bcache in userspace; userspace fsck

1 files changed, 2457 insertions, 0 deletions

diff --git a/libbcache/fs-io.c b/libbcache/fs-io.c
new file mode 100644
index 0000000..942baeb
--- /dev/null
+++ b/libbcache/fs-io.c
@@ -0,0 +1,2457 @@
+
+#include "bcache.h"
+#include "btree_update.h"
+#include "buckets.h"
+#include "clock.h"
+#include "error.h"
+#include "fs.h"
+#include "fs-gc.h"
+#include "fs-io.h"
+#include "inode.h"
+#include "journal.h"
+#include "io.h"
+#include "keylist.h"
+
+#include <linux/aio.h>
+#include <linux/backing-dev.h>
+#include <linux/falloc.h>
+#include <linux/migrate.h>
+#include <linux/mmu_context.h>
+#include <linux/pagevec.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/uio.h>
+#include <linux/writeback.h>
+#include <trace/events/writeback.h>
+
+struct bio_set *bch_writepage_bioset;
+struct bio_set *bch_dio_read_bioset;
+struct bio_set *bch_dio_write_bioset;
+
+/* pagecache_block must be held */
+static int write_invalidate_inode_pages_range(struct address_space *mapping,
+					      loff_t start, loff_t end)
+{
+	int ret;
+
+	/*
+	 * XXX: the way this is currently implemented, we can spin if a process
+	 * is continually redirtying a specific page
+	 */
+	do {
+		if (!mapping->nrpages &&
+		    !mapping->nrexceptional)
+			return 0;
+
+		ret = filemap_write_and_wait_range(mapping, start, end);
+		if (ret)
+			break;
+
+		if (!mapping->nrpages)
+			return 0;
+
+		ret = invalidate_inode_pages2_range(mapping,
+				start >> PAGE_SHIFT,
+				end >> PAGE_SHIFT);
+	} while (ret == -EBUSY);
+
+	return ret;
+}
+
+/* i_size updates: */
+
+static int inode_set_size(struct bch_inode_info *ei, struct bch_inode *bi,
+			  void *p)
+{
+	loff_t *new_i_size = p;
+	unsigned i_flags = le32_to_cpu(bi->i_flags);
+
+	lockdep_assert_held(&ei->update_lock);
+
+	bi->i_size = cpu_to_le64(*new_i_size);
+
+	if (atomic_long_read(&ei->i_size_dirty_count))
+		i_flags |= BCH_INODE_I_SIZE_DIRTY;
+	else
+		i_flags &= ~BCH_INODE_I_SIZE_DIRTY;
+
+	bi->i_flags = cpu_to_le32(i_flags);
+
+	return 0;
+}
+
+static int __must_check bch_write_inode_size(struct cache_set *c,
+					     struct bch_inode_info *ei,
+					     loff_t new_size)
+{
+	return __bch_write_inode(c, ei, inode_set_size, &new_size);
+}
+
+static inline void i_size_dirty_put(struct bch_inode_info *ei)
+{
+	atomic_long_dec_bug(&ei->i_size_dirty_count);
+}
+
+static inline void i_size_dirty_get(struct bch_inode_info *ei)
+{
+	lockdep_assert_held(&ei->vfs_inode.i_rwsem);
+
+	atomic_long_inc(&ei->i_size_dirty_count);
+}
+
+/* i_sectors accounting: */
+
+static enum extent_insert_hook_ret
+i_sectors_hook_fn(struct extent_insert_hook *hook,
+		  struct bpos committed_pos,
+		  struct bpos next_pos,
+		  struct bkey_s_c k,
+		  const struct bkey_i *insert)
+{
+	struct i_sectors_hook *h = container_of(hook,
+				struct i_sectors_hook, hook);
+	s64 sectors = next_pos.offset - committed_pos.offset;
+	int sign = bkey_extent_is_allocation(&insert->k) -
+		(k.k && bkey_extent_is_allocation(k.k));
+
+	EBUG_ON(!(h->ei->i_flags & BCH_INODE_I_SECTORS_DIRTY));
+	EBUG_ON(!atomic_long_read(&h->ei->i_sectors_dirty_count));
+
+	h->sectors += sectors * sign;
+
+	return BTREE_HOOK_DO_INSERT;
+}
+
+static int inode_set_i_sectors_dirty(struct bch_inode_info *ei,
+				    struct bch_inode *bi, void *p)
+{
+	BUG_ON(le32_to_cpu(bi->i_flags) & BCH_INODE_I_SECTORS_DIRTY);
+
+	bi->i_flags = cpu_to_le32(le32_to_cpu(bi->i_flags)|
+				  BCH_INODE_I_SECTORS_DIRTY);
+	return 0;
+}
+
+static int inode_clear_i_sectors_dirty(struct bch_inode_info *ei,
+				       struct bch_inode *bi, void *p)
+{
+	BUG_ON(!(le32_to_cpu(bi->i_flags) & BCH_INODE_I_SECTORS_DIRTY));
+
+	bi->i_sectors	= cpu_to_le64(atomic64_read(&ei->i_sectors));
+	bi->i_flags	= cpu_to_le32(le32_to_cpu(bi->i_flags) &
+				      ~BCH_INODE_I_SECTORS_DIRTY);
+	return 0;
+}
+
+static void i_sectors_dirty_put(struct bch_inode_info *ei,
+				struct i_sectors_hook *h)
+{
+	struct inode *inode = &ei->vfs_inode;
+
+	if (h->sectors) {
+		spin_lock(&inode->i_lock);
+		inode->i_blocks += h->sectors;
+		spin_unlock(&inode->i_lock);
+
+		atomic64_add(h->sectors, &ei->i_sectors);
+		EBUG_ON(atomic64_read(&ei->i_sectors) < 0);
+	}
+
+	EBUG_ON(atomic_long_read(&ei->i_sectors_dirty_count) <= 0);
+
+	mutex_lock(&ei->update_lock);
+
+	if (atomic_long_dec_and_test(&ei->i_sectors_dirty_count)) {
+		struct cache_set *c = ei->vfs_inode.i_sb->s_fs_info;
+		int ret = __bch_write_inode(c, ei, inode_clear_i_sectors_dirty, NULL);
+
+		ret = ret;
+	}
+
+	mutex_unlock(&ei->update_lock);
+}
+
+static int __must_check i_sectors_dirty_get(struct bch_inode_info *ei,
+					    struct i_sectors_hook *h)
+{
+	int ret = 0;
+
+	h->hook.fn	= i_sectors_hook_fn;
+	h->sectors	= 0;
+#ifdef CONFIG_BCACHE_DEBUG
+	h->ei		= ei;
+#endif
+
+	if (atomic_long_inc_not_zero(&ei->i_sectors_dirty_count))
+		return 0;
+
+	mutex_lock(&ei->update_lock);
+
+	if (!(ei->i_flags & BCH_INODE_I_SECTORS_DIRTY)) {
+		struct cache_set *c = ei->vfs_inode.i_sb->s_fs_info;
+
+		ret = __bch_write_inode(c, ei, inode_set_i_sectors_dirty, NULL);
+	}
+
+	if (!ret)
+		atomic_long_inc(&ei->i_sectors_dirty_count);
+
+	mutex_unlock(&ei->update_lock);
+
+	return ret;
+}
+
+struct bchfs_extent_trans_hook {
+	struct bchfs_write_op		*op;
+	struct extent_insert_hook	hook;
+	struct bkey_i_inode		new_inode;
+	bool				need_inode_update;
+};
+
+static enum extent_insert_hook_ret
+bchfs_extent_update_hook(struct extent_insert_hook *hook,
+			 struct bpos committed_pos,
+			 struct bpos next_pos,
+			 struct bkey_s_c k,
+			 const struct bkey_i *insert)
+{
+	struct bchfs_extent_trans_hook *h = container_of(hook,
+				struct bchfs_extent_trans_hook, hook);
+	struct bch_inode_info *ei = h->op->ei;
+	struct inode *inode = &ei->vfs_inode;
+	int sign = bkey_extent_is_allocation(&insert->k) -
+		(k.k && bkey_extent_is_allocation(k.k));
+	s64 sectors = (s64) (next_pos.offset - committed_pos.offset) * sign;
+	u64 offset = min(next_pos.offset << 9, h->op->new_i_size);
+
+	BUG_ON((next_pos.offset << 9) > round_up(offset, PAGE_SIZE));
+
+	/* XXX: ei->i_size locking */
+	if (offset > ei->i_size) {
+		BUG_ON(ei->i_flags & BCH_INODE_I_SIZE_DIRTY);
+
+		if (!h->need_inode_update) {
+			h->need_inode_update = true;
+			return BTREE_HOOK_RESTART_TRANS;
+		}
+
+		h->new_inode.v.i_size = cpu_to_le64(offset);
+		ei->i_size = offset;
+
+		if (h->op->is_dio)
+			i_size_write(inode, offset);
+	}
+
+	if (sectors) {
+		if (!h->need_inode_update) {
+			h->need_inode_update = true;
+			return BTREE_HOOK_RESTART_TRANS;
+		}
+
+		le64_add_cpu(&h->new_inode.v.i_sectors, sectors);
+		atomic64_add(sectors, &ei->i_sectors);
+
+		h->op->sectors_added += sectors;
+
+		if (h->op->is_dio) {
+			spin_lock(&inode->i_lock);
+			inode->i_blocks += sectors;
+			spin_unlock(&inode->i_lock);
+		}
+	}
+
+	return BTREE_HOOK_DO_INSERT;
+}
+
+static int bchfs_write_index_update(struct bch_write_op *wop)
+{
+	struct bchfs_write_op *op = container_of(wop,
+				struct bchfs_write_op, op);
+	struct keylist *keys = &op->op.insert_keys;
+	struct btree_iter extent_iter, inode_iter;
+	struct bchfs_extent_trans_hook hook;
+	struct bkey_i *k = bch_keylist_front(keys);
+	int ret;
+
+	BUG_ON(k->k.p.inode != op->ei->vfs_inode.i_ino);
+
+	bch_btree_iter_init_intent(&extent_iter, wop->c, BTREE_ID_EXTENTS,
+				   bkey_start_pos(&bch_keylist_front(keys)->k));
+	bch_btree_iter_init_intent(&inode_iter, wop->c,	BTREE_ID_INODES,
+				   POS(extent_iter.pos.inode, 0));
+
+	hook.op			= op;
+	hook.hook.fn		= bchfs_extent_update_hook;
+	hook.need_inode_update	= false;
+
+	do {
+		ret = bch_btree_iter_traverse(&extent_iter);
+		if (ret)
+			goto err;
+
+		/* XXX: ei->i_size locking */
+		k = bch_keylist_front(keys);
+		if (min(k->k.p.offset << 9, op->new_i_size) > op->ei->i_size)
+			hook.need_inode_update = true;
+
+		if (hook.need_inode_update) {
+			struct bkey_s_c inode;
+
+			if (!btree_iter_linked(&inode_iter))
+				bch_btree_iter_link(&extent_iter, &inode_iter);
+
+			inode = bch_btree_iter_peek_with_holes(&inode_iter);
+			if ((ret = btree_iter_err(inode)))
+				goto err;
+
+			if (WARN_ONCE(inode.k->type != BCH_INODE_FS,
+				      "inode %llu not found when updating",
+				      extent_iter.pos.inode)) {
+				ret = -ENOENT;
+				break;
+			}
+
+			bkey_reassemble(&hook.new_inode.k_i, inode);
+
+			ret = bch_btree_insert_at(wop->c, &wop->res,
+					&hook.hook, op_journal_seq(wop),
+					BTREE_INSERT_NOFAIL|BTREE_INSERT_ATOMIC,
+					BTREE_INSERT_ENTRY(&extent_iter, k),
+					BTREE_INSERT_ENTRY(&inode_iter, &hook.new_inode.k_i));
+		} else {
+			ret = bch_btree_insert_at(wop->c, &wop->res,
+					&hook.hook, op_journal_seq(wop),
+					BTREE_INSERT_NOFAIL|BTREE_INSERT_ATOMIC,
+					BTREE_INSERT_ENTRY(&extent_iter, k));
+		}
+err:
+		if (ret == -EINTR)
+			continue;
+		if (ret)
+			break;
+
+		bch_keylist_pop_front(keys);
+	} while (!bch_keylist_empty(keys));
+
+	bch_btree_iter_unlock(&extent_iter);
+	bch_btree_iter_unlock(&inode_iter);
+
+	return ret;
+}
+
+/* page state: */
+
+/* stored in page->private: */
+
+/*
+ * bch_page_state has to (unfortunately) be manipulated with cmpxchg - we could
+ * almost protected it with the page lock, except that bch_writepage_io_done has
+ * to update the sector counts (and from interrupt/bottom half context).
+ */
+struct bch_page_state {
+union { struct {
+	/*
+	 * BCH_PAGE_ALLOCATED: page is _fully_ written on disk, and not
+	 * compressed - which means to write this page we don't have to reserve
+	 * space (the new write will never take up more space on disk than what
+	 * it's overwriting)
+	 *
+	 * BCH_PAGE_UNALLOCATED: page is not fully written on disk, or is
+	 * compressed - before writing we have to reserve space with
+	 * bch_reserve_sectors()
+	 *
+	 * BCH_PAGE_RESERVED: page has space reserved on disk (reservation will
+	 * be consumed when the page is written).
+	 */
+	enum {
+		BCH_PAGE_UNALLOCATED	= 0,
+		BCH_PAGE_ALLOCATED,
+	}			alloc_state:2;
+
+	/* Owns PAGE_SECTORS sized reservation: */
+	unsigned		reserved:1;
+
+	/*
+	 * Number of sectors on disk - for i_blocks
+	 * Uncompressed size, not compressed size:
+	 */
+	u8			sectors;
+	u8			dirty_sectors;
+};
+	/* for cmpxchg: */
+	unsigned long		v;
+};
+};
+
+#define page_state_cmpxchg(_ptr, _new, _expr)				\
+({									\
+	unsigned long _v = READ_ONCE((_ptr)->v);			\
+	struct bch_page_state _old;					\
+									\
+	do {								\
+		_old.v = _new.v = _v;					\
+		_expr;							\
+									\
+		EBUG_ON(_new.sectors + _new.dirty_sectors > PAGE_SECTORS);\
+	} while (_old.v != _new.v &&					\
+		 (_v = cmpxchg(&(_ptr)->v, _old.v, _new.v)) != _old.v);	\
+									\
+	_old;								\
+})
+
+static inline struct bch_page_state *page_state(struct page *page)
+{
+	struct bch_page_state *s = (void *) &page->private;
+
+	BUILD_BUG_ON(sizeof(*s) > sizeof(page->private));
+
+	if (!PagePrivate(page))
+		SetPagePrivate(page);
+
+	return s;
+}
+
+static void bch_put_page_reservation(struct cache_set *c, struct page *page)
+{
+	struct disk_reservation res = { .sectors = PAGE_SECTORS };
+	struct bch_page_state s;
+
+	s = page_state_cmpxchg(page_state(page), s, {
+		if (!s.reserved)
+			return;
+		s.reserved = 0;
+	});
+
+	bch_disk_reservation_put(c, &res);
+}
+
+static int bch_get_page_reservation(struct cache_set *c, struct page *page,
+				    bool check_enospc)
+{
+	struct bch_page_state *s = page_state(page), new;
+	struct disk_reservation res;
+	int ret = 0;
+
+	BUG_ON(s->alloc_state == BCH_PAGE_ALLOCATED &&
+	       s->sectors != PAGE_SECTORS);
+
+	if (s->reserved ||
+	    s->alloc_state == BCH_PAGE_ALLOCATED)
+		return 0;
+
+	ret = bch_disk_reservation_get(c, &res, PAGE_SECTORS, !check_enospc
+				       ? BCH_DISK_RESERVATION_NOFAIL : 0);
+	if (ret)
+		return ret;
+
+	page_state_cmpxchg(s, new, {
+		if (new.reserved) {
+			bch_disk_reservation_put(c, &res);
+			return 0;
+		}
+		new.reserved = 1;
+	});
+
+	return 0;
+}
+
+static void bch_clear_page_bits(struct page *page)
+{
+	struct inode *inode = page->mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct disk_reservation res = { .sectors = PAGE_SECTORS };
+	struct bch_page_state s;
+
+	if (!PagePrivate(page))
+		return;
+
+	s = xchg(page_state(page), (struct bch_page_state) { .v = 0 });
+	ClearPagePrivate(page);
+
+	if (s.dirty_sectors) {
+		spin_lock(&inode->i_lock);
+		inode->i_blocks -= s.dirty_sectors;
+		spin_unlock(&inode->i_lock);
+	}
+
+	if (s.reserved)
+		bch_disk_reservation_put(c, &res);
+}
+
+int bch_set_page_dirty(struct page *page)
+{
+	struct bch_page_state old, new;
+
+	old = page_state_cmpxchg(page_state(page), new,
+		new.dirty_sectors = PAGE_SECTORS - new.sectors;
+	);
+
+	if (old.dirty_sectors != new.dirty_sectors) {
+		struct inode *inode = page->mapping->host;
+
+		spin_lock(&inode->i_lock);
+		inode->i_blocks += new.dirty_sectors - old.dirty_sectors;
+		spin_unlock(&inode->i_lock);
+	}
+
+	return __set_page_dirty_nobuffers(page);
+}
+
+/* readpages/writepages: */
+
+static bool bio_can_add_page_contig(struct bio *bio, struct page *page)
+{
+	sector_t offset = (sector_t) page->index << (PAGE_SHIFT - 9);
+
+	return bio->bi_vcnt < bio->bi_max_vecs &&
+		bio_end_sector(bio) == offset;
+}
+
+static int bio_add_page_contig(struct bio *bio, struct page *page)
+{
+	sector_t offset = (sector_t) page->index << (PAGE_SHIFT - 9);
+
+	BUG_ON(!bio->bi_max_vecs);
+
+	if (!bio->bi_vcnt)
+		bio->bi_iter.bi_sector = offset;
+	else if (!bio_can_add_page_contig(bio, page))
+		return -1;
+
+	bio->bi_io_vec[bio->bi_vcnt++] = (struct bio_vec) {
+		.bv_page = page,
+		.bv_len = PAGE_SIZE,
+		.bv_offset = 0,
+	};
+
+	bio->bi_iter.bi_size += PAGE_SIZE;
+
+	return 0;
+}
+
+static void bch_readpages_end_io(struct bio *bio)
+{
+	struct bio_vec *bv;
+	int i;
+
+	bio_for_each_segment_all(bv, bio, i) {
+		struct page *page = bv->bv_page;
+
+		if (!bio->bi_error) {
+			SetPageUptodate(page);
+		} else {
+			ClearPageUptodate(page);
+			SetPageError(page);
+		}
+		unlock_page(page);
+	}
+
+	bio_put(bio);
+}
+
+static inline struct page *__readpage_next_page(struct address_space *mapping,
+						struct list_head *pages,
+						unsigned *nr_pages)
+{
+	struct page *page;
+	int ret;
+
+	while (*nr_pages) {
+		page = list_entry(pages->prev, struct page, lru);
+		prefetchw(&page->flags);
+		list_del(&page->lru);
+
+		ret = add_to_page_cache_lru(page, mapping, page->index, GFP_NOFS);
+
+		/* if add_to_page_cache_lru() succeeded, page is locked: */
+		put_page(page);
+
+		if (!ret)
+			return page;
+
+		(*nr_pages)--;
+	}
+
+	return NULL;
+}
+
+#define for_each_readpage_page(_mapping, _pages, _nr_pages, _page)	\
+	for (;								\
+	     ((_page) = __readpage_next_page(_mapping, _pages, &(_nr_pages)));\
+	     (_nr_pages)--)
+
+static void bch_mark_pages_unalloc(struct bio *bio)
+{
+	struct bvec_iter iter;
+	struct bio_vec bv;
+
+	bio_for_each_segment(bv, bio, iter)
+		page_state(bv.bv_page)->alloc_state = BCH_PAGE_UNALLOCATED;
+}
+
+static void bch_add_page_sectors(struct bio *bio, const struct bkey *k)
+{
+	struct bvec_iter iter;
+	struct bio_vec bv;
+
+	bio_for_each_segment(bv, bio, iter) {
+		struct bch_page_state *s = page_state(bv.bv_page);
+
+		/* sectors in @k from the start of this page: */
+		unsigned k_sectors = k->size - (iter.bi_sector - k->p.offset);
+
+		unsigned page_sectors = min(bv.bv_len >> 9, k_sectors);
+
+		BUG_ON(s->sectors + page_sectors > PAGE_SECTORS);
+
+		s->sectors += page_sectors;
+	}
+}
+
+static void bchfs_read(struct cache_set *c, struct bch_read_bio *rbio, u64 inode)
+{
+	struct bio *bio = &rbio->bio;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	struct bio_vec *bv;
+	unsigned i;
+	int ret;
+
+	bch_increment_clock(c, bio_sectors(bio), READ);
+
+	/*
+	 * Initialize page state:
+	 * If a page is partly allocated and partly a hole, we want it to be
+	 * marked BCH_PAGE_UNALLOCATED - so we initially mark all pages
+	 * allocated and then mark them unallocated as we find holes:
+	 *
+	 * Note that the bio hasn't been split yet - it's the only bio that
+	 * points to these pages. As we walk extents and split @bio, that
+	 * necessarily be true, the splits won't necessarily be on page
+	 * boundaries:
+	 */
+	bio_for_each_segment_all(bv, bio, i) {
+		struct bch_page_state *s = page_state(bv->bv_page);
+
+		EBUG_ON(s->reserved);
+
+		s->alloc_state = BCH_PAGE_ALLOCATED;
+		s->sectors = 0;
+	}
+
+	for_each_btree_key_with_holes(&iter, c, BTREE_ID_EXTENTS,
+				      POS(inode, bio->bi_iter.bi_sector), k) {
+		BKEY_PADDED(k) tmp;
+		struct extent_pick_ptr pick;
+		unsigned bytes, sectors;
+		bool is_last;
+
+		bkey_reassemble(&tmp.k, k);
+		bch_btree_iter_unlock(&iter);
+		k = bkey_i_to_s_c(&tmp.k);
+
+		if (!bkey_extent_is_allocation(k.k) ||
+		    bkey_extent_is_compressed(c, k))
+			bch_mark_pages_unalloc(bio);
+
+		bch_extent_pick_ptr(c, k, &pick);
+		if (IS_ERR(pick.ca)) {
+			bcache_io_error(c, bio, "no device to read from");
+			bio_endio(bio);
+			return;
+		}
+
+		sectors = min_t(u64, k.k->p.offset, bio_end_sector(bio)) -
+			bio->bi_iter.bi_sector;
+		bytes = sectors << 9;
+		is_last = bytes == bio->bi_iter.bi_size;
+		swap(bio->bi_iter.bi_size, bytes);
+
+		if (bkey_extent_is_allocation(k.k))
+			bch_add_page_sectors(bio, k.k);
+
+		if (pick.ca) {
+			PTR_BUCKET(pick.ca, &pick.ptr)->read_prio =
+				c->prio_clock[READ].hand;
+
+			bch_read_extent(c, rbio, k, &pick,
+					BCH_READ_RETRY_IF_STALE|
+					BCH_READ_PROMOTE|
+					(is_last ? BCH_READ_IS_LAST : 0));
+		} else {
+			zero_fill_bio_iter(bio, bio->bi_iter);
+
+			if (is_last)
+				bio_endio(bio);
+		}
+
+		if (is_last)
+			return;
+
+		swap(bio->bi_iter.bi_size, bytes);
+		bio_advance(bio, bytes);
+	}
+
+	/*
+	 * If we get here, it better have been because there was an error
+	 * reading a btree node
+	 */
+	ret = bch_btree_iter_unlock(&iter);
+	BUG_ON(!ret);
+	bcache_io_error(c, bio, "btree IO error %i", ret);
+	bio_endio(bio);
+}
+
+int bch_readpages(struct file *file, struct address_space *mapping,
+		  struct list_head *pages, unsigned nr_pages)
+{
+	struct inode *inode = mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct bch_read_bio *rbio = NULL;
+	struct page *page;
+
+	pr_debug("reading %u pages", nr_pages);
+
+	if (current->pagecache_lock != &mapping->add_lock)
+		pagecache_add_get(&mapping->add_lock);
+
+	for_each_readpage_page(mapping, pages, nr_pages, page) {
+again:
+		if (!rbio) {
+			rbio = container_of(bio_alloc_bioset(GFP_NOFS,
+						min_t(unsigned, nr_pages,
+						      BIO_MAX_PAGES),
+						&c->bio_read),
+					   struct bch_read_bio, bio);
+
+			rbio->bio.bi_end_io = bch_readpages_end_io;
+		}
+
+		if (bio_add_page_contig(&rbio->bio, page)) {
+			bchfs_read(c, rbio, inode->i_ino);
+			rbio = NULL;
+			goto again;
+		}
+	}
+
+	if (rbio)
+		bchfs_read(c, rbio, inode->i_ino);
+
+	if (current->pagecache_lock != &mapping->add_lock)
+		pagecache_add_put(&mapping->add_lock);
+
+	pr_debug("success");
+	return 0;
+}
+
+int bch_readpage(struct file *file, struct page *page)
+{
+	struct address_space *mapping = page->mapping;
+	struct inode *inode = mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct bch_read_bio *rbio;
+
+	rbio = container_of(bio_alloc_bioset(GFP_NOFS, 1,
+					    &c->bio_read),
+			   struct bch_read_bio, bio);
+	bio_set_op_attrs(&rbio->bio, REQ_OP_READ, REQ_SYNC);
+	rbio->bio.bi_end_io = bch_readpages_end_io;
+
+	bio_add_page_contig(&rbio->bio, page);
+	bchfs_read(c, rbio, inode->i_ino);
+
+	return 0;
+}
+
+struct bch_writepage_state {
+	struct bch_writepage_io	*io;
+};
+
+static void bch_writepage_io_free(struct closure *cl)
+{
+	struct bch_writepage_io *io = container_of(cl,
+					struct bch_writepage_io, cl);
+	struct bio *bio = &io->bio.bio;
+
+	bio_put(bio);
+}
+
+static void bch_writepage_io_done(struct closure *cl)
+{
+	struct bch_writepage_io *io = container_of(cl,
+					struct bch_writepage_io, cl);
+	struct cache_set *c = io->op.op.c;
+	struct bio *bio = &io->bio.bio;
+	struct bio_vec *bvec;
+	unsigned i;
+
+	atomic_sub(bio->bi_vcnt, &c->writeback_pages);
+	wake_up(&c->writeback_wait);
+
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->bv_page;
+
+		if (io->op.op.error) {
+			SetPageError(page);
+			if (page->mapping)
+				set_bit(AS_EIO, &page->mapping->flags);
+		}
+
+		if (io->op.op.written >= PAGE_SECTORS) {
+			struct bch_page_state old, new;
+
+			old = page_state_cmpxchg(page_state(page), new, {
+				new.sectors = PAGE_SECTORS;
+				new.dirty_sectors = 0;
+			});
+
+			io->op.sectors_added -= old.dirty_sectors;
+			io->op.op.written -= PAGE_SECTORS;
+		}
+	}
+
+	/*
+	 * racing with fallocate can cause us to add fewer sectors than
+	 * expected - but we shouldn't add more sectors than expected:
+	 *
+	 * (error (due to going RO) halfway through a page can screw that up
+	 * slightly)
+	 */
+	BUG_ON(io->op.sectors_added >= (s64) PAGE_SECTORS);
+
+	/*
+	 * PageWriteback is effectively our ref on the inode - fixup i_blocks
+	 * before calling end_page_writeback:
+	 */
+	if (io->op.sectors_added) {
+		struct inode *inode = &io->op.ei->vfs_inode;
+
+		spin_lock(&inode->i_lock);
+		inode->i_blocks += io->op.sectors_added;
+		spin_unlock(&inode->i_lock);
+	}
+
+	bio_for_each_segment_all(bvec, bio, i)
+		end_page_writeback(bvec->bv_page);
+
+	closure_return_with_destructor(&io->cl, bch_writepage_io_free);
+}
+
+static void bch_writepage_do_io(struct bch_writepage_state *w)
+{
+	struct bch_writepage_io *io = w->io;
+
+	w->io = NULL;
+	atomic_add(io->bio.bio.bi_vcnt, &io->op.op.c->writeback_pages);
+
+	io->op.op.pos.offset = io->bio.bio.bi_iter.bi_sector;
+
+	closure_call(&io->op.op.cl, bch_write, NULL, &io->cl);
+	continue_at(&io->cl, bch_writepage_io_done, NULL);
+}
+
+/*
+ * Get a bch_writepage_io and add @page to it - appending to an existing one if
+ * possible, else allocating a new one:
+ */
+static void bch_writepage_io_alloc(struct cache_set *c,
+				   struct bch_writepage_state *w,
+				   struct bch_inode_info *ei,
+				   struct page *page)
+{
+	u64 inum = ei->vfs_inode.i_ino;
+
+	if (!w->io) {
+alloc_io:
+		w->io = container_of(bio_alloc_bioset(GFP_NOFS,
+						      BIO_MAX_PAGES,
+						      bch_writepage_bioset),
+				     struct bch_writepage_io, bio.bio);
+
+		closure_init(&w->io->cl, NULL);
+		w->io->op.ei		= ei;
+		w->io->op.sectors_added	= 0;
+		w->io->op.is_dio	= false;
+		bch_write_op_init(&w->io->op.op, c, &w->io->bio,
+				  (struct disk_reservation) {
+					.nr_replicas = c->opts.data_replicas,
+				  },
+				  foreground_write_point(c, inum),
+				  POS(inum, 0),
+				  &ei->journal_seq, 0);
+		w->io->op.op.index_update_fn = bchfs_write_index_update;
+	}
+
+	if (bio_add_page_contig(&w->io->bio.bio, page)) {
+		bch_writepage_do_io(w);
+		goto alloc_io;
+	}
+
+	/*
+	 * We shouldn't ever be handed pages for multiple inodes in a single
+	 * pass - right?
+	 */
+	BUG_ON(ei != w->io->op.ei);
+}
+
+static int __bch_writepage(struct cache_set *c, struct page *page,
+			   struct writeback_control *wbc,
+			   struct bch_writepage_state *w)
+{
+	struct inode *inode = page->mapping->host;
+	struct bch_inode_info *ei = to_bch_ei(inode);
+	struct bch_page_state new, old;
+	unsigned offset;
+	loff_t i_size = i_size_read(inode);
+	pgoff_t end_index = i_size >> PAGE_SHIFT;
+
+	EBUG_ON(!PageUptodate(page));
+
+	/* Is the page fully inside i_size? */
+	if (page->index < end_index)
+		goto do_io;
+
+	/* Is the page fully outside i_size? (truncate in progress) */
+	offset = i_size & (PAGE_SIZE - 1);
+	if (page->index > end_index || !offset) {
+		unlock_page(page);
+		return 0;
+	}
+
+	/*
+	 * The page straddles i_size.  It must be zeroed out on each and every
+	 * writepage invocation because it may be mmapped.  "A file is mapped
+	 * in multiples of the page size.  For a file that is not a multiple of
+	 * the  page size, the remaining memory is zeroed when mapped, and
+	 * writes to that region are not written out to the file."
+	 */
+	zero_user_segment(page, offset, PAGE_SIZE);
+do_io:
+	bch_writepage_io_alloc(c, w, ei, page);
+
+	/* while page is locked: */
+	w->io->op.new_i_size = i_size;
+
+	if (wbc->sync_mode == WB_SYNC_ALL)
+		w->io->bio.bio.bi_opf |= WRITE_SYNC;
+
+	/* Before unlocking the page, transfer reservation to w->io: */
+	old = page_state_cmpxchg(page_state(page), new, {
+		BUG_ON(!new.reserved &&
+		       (new.sectors != PAGE_SECTORS ||
+			new.alloc_state != BCH_PAGE_ALLOCATED));
+
+		if (new.alloc_state == BCH_PAGE_ALLOCATED &&
+		    w->io->op.op.compression_type != BCH_COMPRESSION_NONE)
+			new.alloc_state = BCH_PAGE_UNALLOCATED;
+		else if (!new.reserved)
+			goto out;
+		new.reserved = 0;
+	});
+
+	w->io->op.op.res.sectors += PAGE_SECTORS * (old.reserved - new.reserved);
+out:
+	BUG_ON(PageWriteback(page));
+	set_page_writeback(page);
+	unlock_page(page);
+
+	return 0;
+}
+
+int bch_writepages(struct address_space *mapping, struct writeback_control *wbc)
+{
+	struct cache_set *c = mapping->host->i_sb->s_fs_info;
+	struct bch_writepage_state w = { NULL };
+	struct pagecache_iter iter;
+	struct page *page;
+	int ret = 0;
+	int done = 0;
+	pgoff_t uninitialized_var(writeback_index);
+	pgoff_t index;
+	pgoff_t end;		/* Inclusive */
+	pgoff_t done_index;
+	int cycled;
+	int range_whole = 0;
+	int tag;
+
+	if (wbc->range_cyclic) {
+		writeback_index = mapping->writeback_index; /* prev offset */
+		index = writeback_index;
+		if (index == 0)
+			cycled = 1;
+		else
+			cycled = 0;
+		end = -1;
+	} else {
+		index = wbc->range_start >> PAGE_SHIFT;
+		end = wbc->range_end >> PAGE_SHIFT;
+		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+			range_whole = 1;
+		cycled = 1; /* ignore range_cyclic tests */
+	}
+	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+		tag = PAGECACHE_TAG_TOWRITE;
+	else
+		tag = PAGECACHE_TAG_DIRTY;
+retry:
+	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+		tag_pages_for_writeback(mapping, index, end);
+
+	done_index = index;
+get_pages:
+	for_each_pagecache_tag(&iter, mapping, tag, index, end, page) {
+		done_index = page->index;
+
+		if (w.io &&
+		    !bio_can_add_page_contig(&w.io->bio.bio, page))
+			bch_writepage_do_io(&w);
+
+		if (!w.io &&
+		    atomic_read(&c->writeback_pages) >=
+		    c->writeback_pages_max) {
+			/* don't sleep with pages pinned: */
+			pagecache_iter_release(&iter);
+
+			__wait_event(c->writeback_wait,
+				     atomic_read(&c->writeback_pages) <
+				     c->writeback_pages_max);
+			goto get_pages;
+		}
+
+		lock_page(page);
+
+		/*
+		 * Page truncated or invalidated. We can freely skip it
+		 * then, even for data integrity operations: the page
+		 * has disappeared concurrently, so there could be no
+		 * real expectation of this data interity operation
+		 * even if there is now a new, dirty page at the same
+		 * pagecache address.
+		 */
+		if (unlikely(page->mapping != mapping)) {
+continue_unlock:
+			unlock_page(page);
+			continue;
+		}
+
+		if (!PageDirty(page)) {
+			/* someone wrote it for us */
+			goto continue_unlock;
+		}
+
+		if (PageWriteback(page)) {
+			if (wbc->sync_mode != WB_SYNC_NONE)
+				wait_on_page_writeback(page);
+			else
+				goto continue_unlock;
+		}
+
+		BUG_ON(PageWriteback(page));
+		if (!clear_page_dirty_for_io(page))
+			goto continue_unlock;
+
+		trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
+		ret = __bch_writepage(c, page, wbc, &w);
+		if (unlikely(ret)) {
+			if (ret == AOP_WRITEPAGE_ACTIVATE) {
+				unlock_page(page);
+				ret = 0;
+			} else {
+				/*
+				 * done_index is set past this page,
+				 * so media errors will not choke
+				 * background writeout for the entire
+				 * file. This has consequences for
+				 * range_cyclic semantics (ie. it may
+				 * not be suitable for data integrity
+				 * writeout).
+				 */
+				done_index = page->index + 1;
+				done = 1;
+				break;
+			}
+		}
+
+		/*
+		 * We stop writing back only if we are not doing
+		 * integrity sync. In case of integrity sync we have to
+		 * keep going until we have written all the pages
+		 * we tagged for writeback prior to entering this loop.
+		 */
+		if (--wbc->nr_to_write <= 0 &&
+		    wbc->sync_mode == WB_SYNC_NONE) {
+			done = 1;
+			break;
+		}
+	}
+	pagecache_iter_release(&iter);
+
+	if (w.io)
+		bch_writepage_do_io(&w);
+
+	if (!cycled && !done) {
+		/*
+		 * range_cyclic:
+		 * We hit the last page and there is more work to be done: wrap
+		 * back to the start of the file
+		 */
+		cycled = 1;
+		index = 0;
+		end = writeback_index - 1;
+		goto retry;
+	}
+	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
+		mapping->writeback_index = done_index;
+
+	return ret;
+}
+
+int bch_writepage(struct page *page, struct writeback_control *wbc)
+{
+	struct cache_set *c = page->mapping->host->i_sb->s_fs_info;
+	struct bch_writepage_state w = { NULL };
+	int ret;
+
+	ret = __bch_writepage(c, page, wbc, &w);
+	if (w.io)
+		bch_writepage_do_io(&w);
+
+	return ret;
+}
+
+static void bch_read_single_page_end_io(struct bio *bio)
+{
+	complete(bio->bi_private);
+}
+
+static int bch_read_single_page(struct page *page,
+				struct address_space *mapping)
+{
+	struct inode *inode = mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct bch_read_bio *rbio;
+	int ret;
+	DECLARE_COMPLETION_ONSTACK(done);
+
+	rbio = container_of(bio_alloc_bioset(GFP_NOFS, 1,
+					     &c->bio_read),
+			    struct bch_read_bio, bio);
+	bio_set_op_attrs(&rbio->bio, REQ_OP_READ, REQ_SYNC);
+	rbio->bio.bi_private = &done;
+	rbio->bio.bi_end_io = bch_read_single_page_end_io;
+	bio_add_page_contig(&rbio->bio, page);
+
+	bchfs_read(c, rbio, inode->i_ino);
+	wait_for_completion(&done);
+
+	ret = rbio->bio.bi_error;
+	bio_put(&rbio->bio);
+
+	if (ret < 0)
+		return ret;
+
+	SetPageUptodate(page);
+	return 0;
+}
+
+int bch_write_begin(struct file *file, struct address_space *mapping,
+		    loff_t pos, unsigned len, unsigned flags,
+		    struct page **pagep, void **fsdata)
+{
+	struct inode *inode = mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	pgoff_t index = pos >> PAGE_SHIFT;
+	unsigned offset = pos & (PAGE_SIZE - 1);
+	struct page *page;
+	int ret = -ENOMEM;
+
+	BUG_ON(inode_unhashed(mapping->host));
+
+	/* Not strictly necessary - same reason as mkwrite(): */
+	pagecache_add_get(&mapping->add_lock);
+
+	page = grab_cache_page_write_begin(mapping, index, flags);
+	if (!page)
+		goto err_unlock;
+
+	if (PageUptodate(page))
+		goto out;
+
+	/* If we're writing entire page, don't need to read it in first: */
+	if (len == PAGE_SIZE)
+		goto out;
+
+	if (!offset && pos + len >= inode->i_size) {
+		zero_user_segment(page, len, PAGE_SIZE);
+		flush_dcache_page(page);
+		goto out;
+	}
+
+	if (index > inode->i_size >> PAGE_SHIFT) {
+		zero_user_segments(page, 0, offset, offset + len, PAGE_SIZE);
+		flush_dcache_page(page);
+		goto out;
+	}
+readpage:
+	ret = bch_read_single_page(page, mapping);
+	if (ret)
+		goto err;
+out:
+	ret = bch_get_page_reservation(c, page, true);
+	if (ret) {
+		if (!PageUptodate(page)) {
+			/*
+			 * If the page hasn't been read in, we won't know if we
+			 * actually need a reservation - we don't actually need
+			 * to read here, we just need to check if the page is
+			 * fully backed by uncompressed data:
+			 */
+			goto readpage;
+		}
+
+		goto err;
+	}
+
+	*pagep = page;
+	return 0;
+err:
+	unlock_page(page);
+	put_page(page);
+	*pagep = NULL;
+err_unlock:
+	pagecache_add_put(&mapping->add_lock);
+	return ret;
+}
+
+int bch_write_end(struct file *filp, struct address_space *mapping,
+		  loff_t pos, unsigned len, unsigned copied,
+		  struct page *page, void *fsdata)
+{
+	struct inode *inode = page->mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+
+	lockdep_assert_held(&inode->i_rwsem);
+
+	if (unlikely(copied < len && !PageUptodate(page))) {
+		/*
+		 * The page needs to be read in, but that would destroy
+		 * our partial write - simplest thing is to just force
+		 * userspace to redo the write:
+		 */
+		zero_user(page, 0, PAGE_SIZE);
+		flush_dcache_page(page);
+		copied = 0;
+	}
+
+	if (pos + copied > inode->i_size)
+		i_size_write(inode, pos + copied);
+
+	if (copied) {
+		if (!PageUptodate(page))
+			SetPageUptodate(page);
+		if (!PageDirty(page))
+			set_page_dirty(page);
+	} else {
+		bch_put_page_reservation(c, page);
+	}
+
+	unlock_page(page);
+	put_page(page);
+	pagecache_add_put(&mapping->add_lock);
+
+	return copied;
+}
+
+/* O_DIRECT */
+
+static void bch_dio_read_complete(struct closure *cl)
+{
+	struct dio_read *dio = container_of(cl, struct dio_read, cl);
+
+	dio->req->ki_complete(dio->req, dio->ret, 0);
+	bio_check_pages_dirty(&dio->rbio.bio);	/* transfers ownership */
+}
+
+static void bch_direct_IO_read_endio(struct bio *bio)
+{
+	struct dio_read *dio = bio->bi_private;
+
+	if (bio->bi_error)
+		dio->ret = bio->bi_error;
+
+	closure_put(&dio->cl);
+}
+
+static void bch_direct_IO_read_split_endio(struct bio *bio)
+{
+	bch_direct_IO_read_endio(bio);
+	bio_check_pages_dirty(bio);	/* transfers ownership */
+}
+
+static int bch_direct_IO_read(struct cache_set *c, struct kiocb *req,
+			      struct file *file, struct inode *inode,
+			      struct iov_iter *iter, loff_t offset)
+{
+	struct dio_read *dio;
+	struct bio *bio;
+	bool sync = is_sync_kiocb(req);
+	ssize_t ret;
+
+	if ((offset|iter->count) & (block_bytes(c) - 1))
+		return -EINVAL;
+
+	ret = min_t(loff_t, iter->count,
+		    max_t(loff_t, 0, i_size_read(inode) - offset));
+	iov_iter_truncate(iter, round_up(ret, block_bytes(c)));
+
+	if (!ret)
+		return ret;
+
+	bio = bio_alloc_bioset(GFP_KERNEL,
+			       iov_iter_npages(iter, BIO_MAX_PAGES),
+			       bch_dio_read_bioset);
+
+	bio->bi_end_io = bch_direct_IO_read_endio;
+
+	dio = container_of(bio, struct dio_read, rbio.bio);
+	closure_init(&dio->cl, NULL);
+
+	/*
+	 * this is a _really_ horrible hack just to avoid an atomic sub at the
+	 * end:
+	 */
+	if (!sync) {
+		set_closure_fn(&dio->cl, bch_dio_read_complete, NULL);
+		atomic_set(&dio->cl.remaining,
+			   CLOSURE_REMAINING_INITIALIZER -
+			   CLOSURE_RUNNING +
+			   CLOSURE_DESTRUCTOR);
+	} else {
+		atomic_set(&dio->cl.remaining,
+			   CLOSURE_REMAINING_INITIALIZER + 1);
+	}
+
+	dio->req	= req;
+	dio->ret	= ret;
+
+	goto start;
+	while (iter->count) {
+		bio = bio_alloc_bioset(GFP_KERNEL,
+				       iov_iter_npages(iter, BIO_MAX_PAGES),
+				       &c->bio_read);
+		bio->bi_end_io		= bch_direct_IO_read_split_endio;
+start:
+		bio_set_op_attrs(bio, REQ_OP_READ, REQ_SYNC);
+		bio->bi_iter.bi_sector	= offset >> 9;
+		bio->bi_private		= dio;
+
+		ret = bio_get_user_pages(bio, iter, 1);
+		if (ret < 0) {
+			/* XXX: fault inject this path */
+			bio->bi_error = ret;
+			bio_endio(bio);
+			break;
+		}
+
+		offset += bio->bi_iter.bi_size;
+		bio_set_pages_dirty(bio);
+
+		if (iter->count)
+			closure_get(&dio->cl);
+
+		bch_read(c, container_of(bio,
+				struct bch_read_bio, bio),
+			 inode->i_ino);
+	}
+
+	if (sync) {
+		closure_sync(&dio->cl);
+		closure_debug_destroy(&dio->cl);
+		ret = dio->ret;
+		bio_check_pages_dirty(&dio->rbio.bio); /* transfers ownership */
+		return ret;
+	} else {
+		return -EIOCBQUEUED;
+	}
+}
+
+static long __bch_dio_write_complete(struct dio_write *dio)
+{
+	struct file *file = dio->req->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = file->f_inode;
+	long ret = dio->error ?: dio->written;
+
+	bch_disk_reservation_put(dio->c, &dio->res);
+
+	__pagecache_block_put(&mapping->add_lock);
+	inode_dio_end(inode);
+
+	if (dio->iovec && dio->iovec != dio->inline_vecs)
+		kfree(dio->iovec);
+
+	bio_put(&dio->bio.bio);
+	return ret;
+}
+
+static void bch_dio_write_complete(struct closure *cl)
+{
+	struct dio_write *dio = container_of(cl, struct dio_write, cl);
+	struct kiocb *req = dio->req;
+
+	req->ki_complete(req, __bch_dio_write_complete(dio), 0);
+}
+
+static void bch_dio_write_done(struct dio_write *dio)
+{
+	struct bio_vec *bv;
+	int i;
+
+	dio->written += dio->iop.op.written << 9;
+
+	if (dio->iop.op.error)
+		dio->error = dio->iop.op.error;
+
+	bio_for_each_segment_all(bv, &dio->bio.bio, i)
+		put_page(bv->bv_page);
+
+	if (dio->iter.count)
+		bio_reset(&dio->bio.bio);
+}
+
+static void bch_do_direct_IO_write(struct dio_write *dio)
+{
+	struct file *file = dio->req->ki_filp;
+	struct inode *inode = file->f_inode;
+	struct bch_inode_info *ei = to_bch_ei(inode);
+	struct bio *bio = &dio->bio.bio;
+	unsigned flags = 0;
+	int ret;
+
+	if ((dio->req->ki_flags & IOCB_DSYNC) &&
+	    !dio->c->opts.journal_flush_disabled)
+		flags |= BCH_WRITE_FLUSH;
+
+	bio->bi_iter.bi_sector = (dio->offset + dio->written) >> 9;
+
+	ret = bio_get_user_pages(bio, &dio->iter, 0);
+	if (ret < 0) {
+		/*
+		 * these didn't get initialized, but bch_dio_write_done() will
+		 * look at them:
+		 */
+		dio->iop.op.error = 0;
+		dio->iop.op.written = 0;
+		dio->error = ret;
+		return;
+	}
+
+	dio->iop.ei		= ei;
+	dio->iop.sectors_added	= 0;
+	dio->iop.is_dio		= true;
+	dio->iop.new_i_size	= U64_MAX;
+	bch_write_op_init(&dio->iop.op, dio->c, &dio->bio,
+			  dio->res,
+			  foreground_write_point(dio->c, inode->i_ino),
+			  POS(inode->i_ino, bio->bi_iter.bi_sector),
+			  &ei->journal_seq, flags);
+	dio->iop.op.index_update_fn = bchfs_write_index_update;
+
+	dio->res.sectors -= bio_sectors(bio);
+	dio->iop.op.res.sectors = bio_sectors(bio);
+
+	task_io_account_write(bio->bi_iter.bi_size);
+
+	closure_call(&dio->iop.op.cl, bch_write, NULL, &dio->cl);
+}
+
+static void bch_dio_write_loop_async(struct closure *cl)
+{
+	struct dio_write *dio =
+		container_of(cl, struct dio_write, cl);
+	struct address_space *mapping = dio->req->ki_filp->f_mapping;
+
+	bch_dio_write_done(dio);
+
+	if (dio->iter.count && !dio->error) {
+		use_mm(dio->mm);
+		pagecache_block_get(&mapping->add_lock);
+
+		bch_do_direct_IO_write(dio);
+
+		pagecache_block_put(&mapping->add_lock);
+		unuse_mm(dio->mm);
+
+		continue_at(&dio->cl, bch_dio_write_loop_async, NULL);
+	} else {
+#if 0
+		closure_return_with_destructor(cl, bch_dio_write_complete);
+#else
+		closure_debug_destroy(cl);
+		bch_dio_write_complete(cl);
+#endif
+	}
+}
+
+static int bch_direct_IO_write(struct cache_set *c, struct kiocb *req,
+			       struct file *file, struct inode *inode,
+			       struct iov_iter *iter, loff_t offset)
+{
+	struct address_space *mapping = file->f_mapping;
+	struct dio_write *dio;
+	struct bio *bio;
+	ssize_t ret;
+	bool sync = is_sync_kiocb(req);
+
+	lockdep_assert_held(&inode->i_rwsem);
+
+	if (unlikely(!iter->count))
+		return 0;
+
+	if (unlikely((offset|iter->count) & (block_bytes(c) - 1)))
+		return -EINVAL;
+
+	bio = bio_alloc_bioset(GFP_KERNEL,
+			       iov_iter_npages(iter, BIO_MAX_PAGES),
+			       bch_dio_write_bioset);
+	dio = container_of(bio, struct dio_write, bio.bio);
+	dio->req	= req;
+	dio->c		= c;
+	dio->written	= 0;
+	dio->error	= 0;
+	dio->offset	= offset;
+	dio->iovec	= NULL;
+	dio->iter	= *iter;
+	dio->mm		= current->mm;
+	closure_init(&dio->cl, NULL);
+
+	if (offset + iter->count > inode->i_size)
+		sync = true;
+
+	/*
+	 * XXX: we shouldn't return -ENOSPC if we're overwriting existing data -
+	 * if getting a reservation fails we should check if we are doing an
+	 * overwrite.
+	 *
+	 * Have to then guard against racing with truncate (deleting data that
+	 * we would have been overwriting)
+	 */
+	ret = bch_disk_reservation_get(c, &dio->res, iter->count >> 9, 0);
+	if (unlikely(ret)) {
+		closure_debug_destroy(&dio->cl);
+		bio_put(bio);
+		return ret;
+	}
+
+	inode_dio_begin(inode);
+	__pagecache_block_get(&mapping->add_lock);
+
+	if (sync) {
+		do {
+			bch_do_direct_IO_write(dio);
+
+			closure_sync(&dio->cl);
+			bch_dio_write_done(dio);
+		} while (dio->iter.count && !dio->error);
+
+		closure_debug_destroy(&dio->cl);
+		return __bch_dio_write_complete(dio);
+	} else {
+		bch_do_direct_IO_write(dio);
+
+		if (dio->iter.count && !dio->error) {
+			if (dio->iter.nr_segs > ARRAY_SIZE(dio->inline_vecs)) {
+				dio->iovec = kmalloc(dio->iter.nr_segs *
+						     sizeof(struct iovec),
+						     GFP_KERNEL);
+				if (!dio->iovec)
+					dio->error = -ENOMEM;
+			} else {
+				dio->iovec = dio->inline_vecs;
+			}
+
+			memcpy(dio->iovec,
+			       dio->iter.iov,
+			       dio->iter.nr_segs * sizeof(struct iovec));
+			dio->iter.iov = dio->iovec;
+		}
+
+		continue_at_noreturn(&dio->cl, bch_dio_write_loop_async, NULL);
+		return -EIOCBQUEUED;
+	}
+}
+
+ssize_t bch_direct_IO(struct kiocb *req, struct iov_iter *iter)
+{
+	struct file *file = req->ki_filp;
+	struct inode *inode = file->f_inode;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+
+	return ((iov_iter_rw(iter) == WRITE)
+		? bch_direct_IO_write
+		: bch_direct_IO_read)(c, req, file, inode, iter, req->ki_pos);
+}
+
+static ssize_t
+bch_direct_write(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file->f_inode;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct address_space *mapping = file->f_mapping;
+	loff_t pos = iocb->ki_pos;
+	ssize_t	ret;
+
+	pagecache_block_get(&mapping->add_lock);
+
+	/* Write and invalidate pagecache range that we're writing to: */
+	ret = write_invalidate_inode_pages_range(file->f_mapping, pos,
+					pos + iov_iter_count(iter) - 1);
+	if (unlikely(ret))
+		goto err;
+
+	ret = bch_direct_IO_write(c, iocb, file, inode, iter, pos);
+err:
+	pagecache_block_put(&mapping->add_lock);
+
+	return ret;
+}
+
+static ssize_t __bch_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	ssize_t	ret;
+
+	/* We can write back this queue in page reclaim */
+	current->backing_dev_info = inode_to_bdi(inode);
+	ret = file_remove_privs(file);
+	if (ret)
+		goto out;
+
+	ret = file_update_time(file);
+	if (ret)
+		goto out;
+
+	ret = iocb->ki_flags & IOCB_DIRECT
+		? bch_direct_write(iocb, from)
+		: generic_perform_write(file, from, iocb->ki_pos);
+
+	if (likely(ret > 0))
+		iocb->ki_pos += ret;
+out:
+	current->backing_dev_info = NULL;
+	return ret;
+}
+
+ssize_t bch_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file->f_mapping->host;
+	bool direct = iocb->ki_flags & IOCB_DIRECT;
+	ssize_t ret;
+
+	inode_lock(inode);
+	ret = generic_write_checks(iocb, from);
+	if (ret > 0)
+		ret = __bch_write_iter(iocb, from);
+	inode_unlock(inode);
+
+	if (ret > 0 && !direct)
+		ret = generic_write_sync(iocb, ret);
+
+	return ret;
+}
+
+int bch_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	struct page *page = vmf->page;
+	struct inode *inode = file_inode(vma->vm_file);
+	struct address_space *mapping = inode->i_mapping;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	int ret = VM_FAULT_LOCKED;
+
+	sb_start_pagefault(inode->i_sb);
+	file_update_time(vma->vm_file);
+
+	/*
+	 * Not strictly necessary, but helps avoid dio writes livelocking in
+	 * write_invalidate_inode_pages_range() - can drop this if/when we get
+	 * a write_invalidate_inode_pages_range() that works without dropping
+	 * page lock before invalidating page
+	 */
+	if (current->pagecache_lock != &mapping->add_lock)
+		pagecache_add_get(&mapping->add_lock);
+
+	lock_page(page);
+	if (page->mapping != mapping ||
+	    page_offset(page) > i_size_read(inode)) {
+		unlock_page(page);
+		ret = VM_FAULT_NOPAGE;
+		goto out;
+	}
+
+	if (bch_get_page_reservation(c, page, true)) {
+		unlock_page(page);
+		ret = VM_FAULT_SIGBUS;
+		goto out;
+	}
+
+	if (!PageDirty(page))
+		set_page_dirty(page);
+	wait_for_stable_page(page);
+out:
+	if (current->pagecache_lock != &mapping->add_lock)
+		pagecache_add_put(&mapping->add_lock);
+	sb_end_pagefault(inode->i_sb);
+	return ret;
+}
+
+void bch_invalidatepage(struct page *page, unsigned int offset,
+			unsigned int length)
+{
+	EBUG_ON(!PageLocked(page));
+	EBUG_ON(PageWriteback(page));
+
+	if (offset || length < PAGE_SIZE)
+		return;
+
+	bch_clear_page_bits(page);
+}
+
+int bch_releasepage(struct page *page, gfp_t gfp_mask)
+{
+	EBUG_ON(!PageLocked(page));
+	EBUG_ON(PageWriteback(page));
+
+	if (PageDirty(page))
+		return 0;
+
+	bch_clear_page_bits(page);
+	return 1;
+}
+
+#ifdef CONFIG_MIGRATION
+int bch_migrate_page(struct address_space *mapping, struct page *newpage,
+		     struct page *page, enum migrate_mode mode)
+{
+	int ret;
+
+	ret = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
+	if (ret != MIGRATEPAGE_SUCCESS)
+		return ret;
+
+	if (PagePrivate(page)) {
+		*page_state(newpage) = *page_state(page);
+		ClearPagePrivate(page);
+	}
+
+	migrate_page_copy(newpage, page);
+	return MIGRATEPAGE_SUCCESS;
+}
+#endif
+
+int bch_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct bch_inode_info *ei = to_bch_ei(inode);
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	int ret;
+
+	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (ret)
+		return ret;
+
+	if (c->opts.journal_flush_disabled)
+		return 0;
+
+	return bch_journal_flush_seq(&c->journal, ei->journal_seq);
+}
+
+static int __bch_truncate_page(struct address_space *mapping,
+			       pgoff_t index, loff_t start, loff_t end)
+{
+	struct inode *inode = mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	unsigned start_offset = start & (PAGE_SIZE - 1);
+	unsigned end_offset = ((end - 1) & (PAGE_SIZE - 1)) + 1;
+	struct page *page;
+	int ret = 0;
+
+	/* Page boundary? Nothing to do */
+	if (!((index == start >> PAGE_SHIFT && start_offset) ||
+	      (index == end >> PAGE_SHIFT && end_offset != PAGE_SIZE)))
+		return 0;
+
+	/* Above i_size? */
+	if (index << PAGE_SHIFT >= inode->i_size)
+		return 0;
+
+	page = find_lock_page(mapping, index);
+	if (!page) {
+		struct btree_iter iter;
+		struct bkey_s_c k = bkey_s_c_null;
+
+		/*
+		 * XXX: we're doing two index lookups when we end up reading the
+		 * page
+		 */
+		for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+				   POS(inode->i_ino,
+				       index << (PAGE_SHIFT - 9)), k) {
+			if (bkey_cmp(bkey_start_pos(k.k),
+				     POS(inode->i_ino,
+					 (index + 1) << (PAGE_SHIFT - 9))) >= 0)
+				break;
+
+			if (k.k->type != KEY_TYPE_DISCARD &&
+			    k.k->type != BCH_RESERVATION) {
+				bch_btree_iter_unlock(&iter);
+				goto create;
+			}
+		}
+		bch_btree_iter_unlock(&iter);
+		return 0;
+create:
+		page = find_or_create_page(mapping, index, GFP_KERNEL);
+		if (unlikely(!page)) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	if (!PageUptodate(page)) {
+		ret = bch_read_single_page(page, mapping);
+		if (ret)
+			goto unlock;
+	}
+
+	/*
+	 * Bit of a hack - we don't want truncate to fail due to -ENOSPC.
+	 *
+	 * XXX: because we aren't currently tracking whether the page has actual
+	 * data in it (vs. just 0s, or only partially written) this wrong. ick.
+	 */
+	ret = bch_get_page_reservation(c, page, false);
+	BUG_ON(ret);
+
+	if (index == start >> PAGE_SHIFT &&
+	    index == end >> PAGE_SHIFT)
+		zero_user_segment(page, start_offset, end_offset);
+	else if (index == start >> PAGE_SHIFT)
+		zero_user_segment(page, start_offset, PAGE_SIZE);
+	else if (index == end >> PAGE_SHIFT)
+		zero_user_segment(page, 0, end_offset);
+
+	if (!PageDirty(page))
+		set_page_dirty(page);
+unlock:
+	unlock_page(page);
+	put_page(page);
+out:
+	return ret;
+}
+
+static int bch_truncate_page(struct address_space *mapping, loff_t from)
+{
+	return __bch_truncate_page(mapping, from >> PAGE_SHIFT,
+				   from, from + PAGE_SIZE);
+}
+
+int bch_truncate(struct inode *inode, struct iattr *iattr)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct bch_inode_info *ei = to_bch_ei(inode);
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	bool shrink = iattr->ia_size <= inode->i_size;
+	int ret = 0;
+
+	inode_dio_wait(inode);
+	pagecache_block_get(&mapping->add_lock);
+
+	truncate_setsize(inode, iattr->ia_size);
+
+	/* sync appends.. */
+	/* XXX what protects ei->i_size? */
+	if (iattr->ia_size > ei->i_size)
+		ret = filemap_write_and_wait_range(mapping, ei->i_size, S64_MAX);
+	if (ret)
+		goto err_put_pagecache;
+
+	mutex_lock(&ei->update_lock);
+	i_size_dirty_get(ei);
+	ret = bch_write_inode_size(c, ei, inode->i_size);
+	mutex_unlock(&ei->update_lock);
+
+	if (unlikely(ret))
+		goto err;
+
+	/*
+	 * There might be persistent reservations (from fallocate())
+	 * above i_size, which bch_inode_truncate() will discard - we're
+	 * only supposed to discard them if we're doing a real truncate
+	 * here (new i_size < current i_size):
+	 */
+	if (shrink) {
+		struct i_sectors_hook i_sectors_hook;
+		int ret;
+
+		ret = i_sectors_dirty_get(ei, &i_sectors_hook);
+		if (unlikely(ret))
+			goto err;
+
+		ret = bch_truncate_page(inode->i_mapping, iattr->ia_size);
+		if (unlikely(ret)) {
+			i_sectors_dirty_put(ei, &i_sectors_hook);
+			goto err;
+		}
+
+		ret = bch_inode_truncate(c, inode->i_ino,
+					 round_up(iattr->ia_size, PAGE_SIZE) >> 9,
+					 &i_sectors_hook.hook,
+					 &ei->journal_seq);
+
+		i_sectors_dirty_put(ei, &i_sectors_hook);
+
+		if (unlikely(ret))
+			goto err;
+	}
+
+	mutex_lock(&ei->update_lock);
+	setattr_copy(inode, iattr);
+	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+
+	/* clear I_SIZE_DIRTY: */
+	i_size_dirty_put(ei);
+	ret = bch_write_inode_size(c, ei, inode->i_size);
+	mutex_unlock(&ei->update_lock);
+
+	pagecache_block_put(&mapping->add_lock);
+
+	return 0;
+err:
+	i_size_dirty_put(ei);
+err_put_pagecache:
+	pagecache_block_put(&mapping->add_lock);
+	return ret;
+}
+
+static long bch_fpunch(struct inode *inode, loff_t offset, loff_t len)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct bch_inode_info *ei = to_bch_ei(inode);
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	u64 ino = inode->i_ino;
+	u64 discard_start = round_up(offset, PAGE_SIZE) >> 9;
+	u64 discard_end = round_down(offset + len, PAGE_SIZE) >> 9;
+	int ret = 0;
+
+	inode_lock(inode);
+	inode_dio_wait(inode);
+	pagecache_block_get(&mapping->add_lock);
+
+	ret = __bch_truncate_page(inode->i_mapping,
+				  offset >> PAGE_SHIFT,
+				  offset, offset + len);
+	if (unlikely(ret))
+		goto out;
+
+	if (offset >> PAGE_SHIFT !=
+	    (offset + len) >> PAGE_SHIFT) {
+		ret = __bch_truncate_page(inode->i_mapping,
+					  (offset + len) >> PAGE_SHIFT,
+					  offset, offset + len);
+		if (unlikely(ret))
+			goto out;
+	}
+
+	truncate_pagecache_range(inode, offset, offset + len - 1);
+
+	if (discard_start < discard_end) {
+		struct disk_reservation disk_res;
+		struct i_sectors_hook i_sectors_hook;
+		int ret;
+
+		BUG_ON(bch_disk_reservation_get(c, &disk_res, 0, 0));
+
+		ret = i_sectors_dirty_get(ei, &i_sectors_hook);
+		if (unlikely(ret))
+			goto out;
+
+		ret = bch_discard(c,
+				  POS(ino, discard_start),
+				  POS(ino, discard_end),
+				  0,
+				  &disk_res,
+				  &i_sectors_hook.hook,
+				  &ei->journal_seq);
+
+		i_sectors_dirty_put(ei, &i_sectors_hook);
+		bch_disk_reservation_put(c, &disk_res);
+	}
+out:
+	pagecache_block_put(&mapping->add_lock);
+	inode_unlock(inode);
+
+	return ret;
+}
+
+static long bch_fcollapse(struct inode *inode, loff_t offset, loff_t len)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct bch_inode_info *ei = to_bch_ei(inode);
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct btree_iter src;
+	struct btree_iter dst;
+	BKEY_PADDED(k) copy;
+	struct bkey_s_c k;
+	struct i_sectors_hook i_sectors_hook;
+	loff_t new_size;
+	int ret;
+
+	if ((offset | len) & (PAGE_SIZE - 1))
+		return -EINVAL;
+
+	bch_btree_iter_init_intent(&dst, c, BTREE_ID_EXTENTS,
+				   POS(inode->i_ino, offset >> 9));
+	/* position will be set from dst iter's position: */
+	bch_btree_iter_init(&src, c, BTREE_ID_EXTENTS, POS_MIN);
+	bch_btree_iter_link(&src, &dst);
+
+	/*
+	 * We need i_mutex to keep the page cache consistent with the extents
+	 * btree, and the btree consistent with i_size - we don't need outside
+	 * locking for the extents btree itself, because we're using linked
+	 * iterators
+	 */
+	inode_lock(inode);
+	inode_dio_wait(inode);
+	pagecache_block_get(&mapping->add_lock);
+
+	ret = -EINVAL;
+	if (offset + len >= inode->i_size)
+		goto err;
+
+	if (inode->i_size < len)
+		goto err;
+
+	new_size = inode->i_size - len;
+
+	ret = write_invalidate_inode_pages_range(inode->i_mapping,
+						 offset, LLONG_MAX);
+	if (ret)
+		goto err;
+
+	ret = i_sectors_dirty_get(ei, &i_sectors_hook);
+	if (ret)
+		goto err;
+
+	while (bkey_cmp(dst.pos,
+			POS(inode->i_ino,
+			    round_up(new_size, PAGE_SIZE) >> 9)) < 0) {
+		struct disk_reservation disk_res;
+
+		bch_btree_iter_set_pos(&src,
+			POS(dst.pos.inode, dst.pos.offset + (len >> 9)));
+
+		ret = bch_btree_iter_traverse(&dst);
+		if (ret)
+			goto btree_iter_err;
+
+		k = bch_btree_iter_peek_with_holes(&src);
+		if ((ret = btree_iter_err(k)))
+			goto btree_iter_err;
+
+		bkey_reassemble(&copy.k, k);
+
+		if (bkey_deleted(&copy.k.k))
+			copy.k.k.type = KEY_TYPE_DISCARD;
+
+		bch_cut_front(src.pos, &copy.k);
+		copy.k.k.p.offset -= len >> 9;
+
+		BUG_ON(bkey_cmp(dst.pos, bkey_start_pos(&copy.k.k)));
+
+		ret = bch_disk_reservation_get(c, &disk_res, copy.k.k.size,
+					       BCH_DISK_RESERVATION_NOFAIL);
+		BUG_ON(ret);
+
+		ret = bch_btree_insert_at(c, &disk_res, &i_sectors_hook.hook,
+					  &ei->journal_seq,
+					  BTREE_INSERT_ATOMIC|
+					  BTREE_INSERT_NOFAIL,
+					  BTREE_INSERT_ENTRY(&dst, &copy.k));
+		bch_disk_reservation_put(c, &disk_res);
+btree_iter_err:
+		if (ret < 0 && ret != -EINTR)
+			goto err_unwind;
+
+		bch_btree_iter_cond_resched(&src);
+	}
+
+	bch_btree_iter_unlock(&src);
+	bch_btree_iter_unlock(&dst);
+
+	ret = bch_inode_truncate(c, inode->i_ino,
+				 round_up(new_size, PAGE_SIZE) >> 9,
+				 &i_sectors_hook.hook,
+				 &ei->journal_seq);
+	if (ret)
+		goto err_unwind;
+
+	i_sectors_dirty_put(ei, &i_sectors_hook);
+
+	mutex_lock(&ei->update_lock);
+	i_size_write(inode, new_size);
+	ret = bch_write_inode_size(c, ei, inode->i_size);
+	mutex_unlock(&ei->update_lock);
+
+	pagecache_block_put(&mapping->add_lock);
+	inode_unlock(inode);
+
+	return ret;
+err_unwind:
+	/*
+	 * XXX: we've left data with multiple pointers... which isn't a _super_
+	 * serious problem...
+	 */
+	i_sectors_dirty_put(ei, &i_sectors_hook);
+err:
+	bch_btree_iter_unlock(&src);
+	bch_btree_iter_unlock(&dst);
+	pagecache_block_put(&mapping->add_lock);
+	inode_unlock(inode);
+	return ret;
+}
+
+static long bch_fallocate(struct inode *inode, int mode,
+			  loff_t offset, loff_t len)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct bch_inode_info *ei = to_bch_ei(inode);
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct i_sectors_hook i_sectors_hook;
+	struct btree_iter iter;
+	struct bkey_i reservation;
+	struct bkey_s_c k;
+	struct bpos end;
+	loff_t block_start, block_end;
+	loff_t new_size = offset + len;
+	unsigned sectors;
+	int ret;
+
+	bch_btree_iter_init_intent(&iter, c, BTREE_ID_EXTENTS, POS_MIN);
+
+	inode_lock(inode);
+	inode_dio_wait(inode);
+	pagecache_block_get(&mapping->add_lock);
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
+	    new_size > inode->i_size) {
+		ret = inode_newsize_ok(inode, new_size);
+		if (ret)
+			goto err;
+	}
+
+	if (mode & FALLOC_FL_ZERO_RANGE) {
+		ret = __bch_truncate_page(inode->i_mapping,
+					  offset >> PAGE_SHIFT,
+					  offset, offset + len);
+
+		if (!ret &&
+		    offset >> PAGE_SHIFT !=
+		    (offset + len) >> PAGE_SHIFT)
+			ret = __bch_truncate_page(inode->i_mapping,
+						  (offset + len) >> PAGE_SHIFT,
+						  offset, offset + len);
+
+		if (unlikely(ret))
+			goto err;
+
+		truncate_pagecache_range(inode, offset, offset + len - 1);
+
+		block_start	= round_up(offset, PAGE_SIZE);
+		block_end	= round_down(offset + len, PAGE_SIZE);
+	} else {
+		block_start	= round_down(offset, PAGE_SIZE);
+		block_end	= round_up(offset + len, PAGE_SIZE);
+	}
+
+	bch_btree_iter_set_pos(&iter, POS(inode->i_ino, block_start >> 9));
+	end = POS(inode->i_ino, block_end >> 9);
+
+	ret = i_sectors_dirty_get(ei, &i_sectors_hook);
+	if (unlikely(ret))
+		goto err;
+
+	while (bkey_cmp(iter.pos, end) < 0) {
+		struct disk_reservation disk_res = { 0 };
+
+		k = bch_btree_iter_peek_with_holes(&iter);
+		if ((ret = btree_iter_err(k)))
+			goto btree_iter_err;
+
+		/* already reserved */
+		if (k.k->type == BCH_RESERVATION) {
+			bch_btree_iter_advance_pos(&iter);
+			continue;
+		}
+
+		if (bkey_extent_is_data(k.k)) {
+			if (!(mode & FALLOC_FL_ZERO_RANGE)) {
+				bch_btree_iter_advance_pos(&iter);
+				continue;
+			}
+		}
+
+		bkey_init(&reservation.k);
+		reservation.k.type	= BCH_RESERVATION;
+		reservation.k.p		= k.k->p;
+		reservation.k.size	= k.k->size;
+
+		bch_cut_front(iter.pos, &reservation);
+		bch_cut_back(end, &reservation.k);
+
+		sectors = reservation.k.size;
+
+		if (!bkey_extent_is_allocation(k.k) ||
+		    bkey_extent_is_compressed(c, k)) {
+			ret = bch_disk_reservation_get(c, &disk_res,
+						       sectors, 0);
+			if (ret)
+				goto err_put_sectors_dirty;
+		}
+
+		ret = bch_btree_insert_at(c, &disk_res, &i_sectors_hook.hook,
+					  &ei->journal_seq,
+					  BTREE_INSERT_ATOMIC|
+					  BTREE_INSERT_NOFAIL,
+					  BTREE_INSERT_ENTRY(&iter, &reservation));
+		bch_disk_reservation_put(c, &disk_res);
+btree_iter_err:
+		if (ret < 0 && ret != -EINTR)
+			goto err_put_sectors_dirty;
+
+	}
+	bch_btree_iter_unlock(&iter);
+
+	i_sectors_dirty_put(ei, &i_sectors_hook);
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
+	    new_size > inode->i_size) {
+		i_size_write(inode, new_size);
+
+		mutex_lock(&ei->update_lock);
+		ret = bch_write_inode_size(c, ei, inode->i_size);
+		mutex_unlock(&ei->update_lock);
+	}
+
+	/* blech */
+	if ((mode & FALLOC_FL_KEEP_SIZE) &&
+	    (mode & FALLOC_FL_ZERO_RANGE) &&
+	    ei->i_size != inode->i_size) {
+		/* sync appends.. */
+		ret = filemap_write_and_wait_range(mapping, ei->i_size, S64_MAX);
+		if (ret)
+			goto err;
+
+		if (ei->i_size != inode->i_size) {
+			mutex_lock(&ei->update_lock);
+			ret = bch_write_inode_size(c, ei, inode->i_size);
+			mutex_unlock(&ei->update_lock);
+		}
+	}
+
+	pagecache_block_put(&mapping->add_lock);
+	inode_unlock(inode);
+
+	return 0;
+err_put_sectors_dirty:
+	i_sectors_dirty_put(ei, &i_sectors_hook);
+err:
+	bch_btree_iter_unlock(&iter);
+	pagecache_block_put(&mapping->add_lock);
+	inode_unlock(inode);
+	return ret;
+}
+
+long bch_fallocate_dispatch(struct file *file, int mode,
+			    loff_t offset, loff_t len)
+{
+	struct inode *inode = file_inode(file);
+
+	if (!(mode & ~(FALLOC_FL_KEEP_SIZE|FALLOC_FL_ZERO_RANGE)))
+		return bch_fallocate(inode, mode, offset, len);
+
+	if (mode == (FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE))
+		return bch_fpunch(inode, offset, len);
+
+	if (mode == FALLOC_FL_COLLAPSE_RANGE)
+		return bch_fcollapse(inode, offset, len);
+
+	return -EOPNOTSUPP;
+}
+
+static bool page_is_data(struct page *page)
+{
+	/* XXX: should only have to check PageDirty */
+	return PagePrivate(page) &&
+		(page_state(page)->sectors ||
+		 page_state(page)->dirty_sectors);
+}
+
+static loff_t bch_next_pagecache_data(struct inode *inode,
+				      loff_t start_offset,
+				      loff_t end_offset)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct page *page;
+	pgoff_t index;
+
+	for (index = start_offset >> PAGE_SHIFT;
+	     index < end_offset >> PAGE_SHIFT;
+	     index++) {
+		if (find_get_pages(mapping, index, 1, &page)) {
+			lock_page(page);
+			index = page->index;
+
+			if (page_is_data(page))
+				end_offset =
+					min(end_offset,
+					max(start_offset,
+					    ((loff_t) index) << PAGE_SHIFT));
+			unlock_page(page);
+			put_page(page);
+		} else {
+			break;
+		}
+	}
+
+	return end_offset;
+}
+
+static loff_t bch_seek_data(struct file *file, u64 offset)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	u64 isize, next_data = MAX_LFS_FILESIZE;
+	int ret;
+
+	isize = i_size_read(inode);
+	if (offset >= isize)
+		return -ENXIO;
+
+	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+			   POS(inode->i_ino, offset >> 9), k) {
+		if (k.k->p.inode != inode->i_ino) {
+			break;
+		} else if (bkey_extent_is_data(k.k)) {
+			next_data = max(offset, bkey_start_offset(k.k) << 9);
+			break;
+		} else if (k.k->p.offset >> 9 > isize)
+			break;
+	}
+
+	ret = bch_btree_iter_unlock(&iter);
+	if (ret)
+		return ret;
+
+	if (next_data > offset)
+		next_data = bch_next_pagecache_data(inode, offset, next_data);
+
+	if (next_data > isize)
+		return -ENXIO;
+
+	return vfs_setpos(file, next_data, MAX_LFS_FILESIZE);
+}
+
+static bool page_slot_is_data(struct address_space *mapping, pgoff_t index)
+{
+	struct page *page;
+	bool ret;
+
+	page = find_lock_entry(mapping, index);
+	if (!page || radix_tree_exception(page))
+		return false;
+
+	ret = page_is_data(page);
+	unlock_page(page);
+
+	return ret;
+}
+
+static loff_t bch_next_pagecache_hole(struct inode *inode,
+				      loff_t start_offset,
+				      loff_t end_offset)
+{
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t index;
+
+	for (index = start_offset >> PAGE_SHIFT;
+	     index < end_offset >> PAGE_SHIFT;
+	     index++)
+		if (!page_slot_is_data(mapping, index))
+			end_offset = max(start_offset,
+					 ((loff_t) index) << PAGE_SHIFT);
+
+	return end_offset;
+}
+
+static loff_t bch_seek_hole(struct file *file, u64 offset)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct cache_set *c = inode->i_sb->s_fs_info;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	u64 isize, next_hole = MAX_LFS_FILESIZE;
+	int ret;
+
+	isize = i_size_read(inode);
+	if (offset >= isize)
+		return -ENXIO;
+
+	for_each_btree_key_with_holes(&iter, c, BTREE_ID_EXTENTS,
+				      POS(inode->i_ino, offset >> 9), k) {
+		if (k.k->p.inode != inode->i_ino) {
+			next_hole = bch_next_pagecache_hole(inode,
+					offset, MAX_LFS_FILESIZE);
+			break;
+		} else if (!bkey_extent_is_data(k.k)) {
+			next_hole = bch_next_pagecache_hole(inode,
+					max(offset, bkey_start_offset(k.k) << 9),
+					k.k->p.offset << 9);
+
+			if (next_hole < k.k->p.offset << 9)
+				break;
+		} else {
+			offset = max(offset, bkey_start_offset(k.k) << 9);
+		}
+	}
+
+	ret = bch_btree_iter_unlock(&iter);
+	if (ret)
+		return ret;
+
+	if (next_hole > isize)
+		next_hole = isize;
+
+	return vfs_setpos(file, next_hole, MAX_LFS_FILESIZE);
+}
+
+loff_t bch_llseek(struct file *file, loff_t offset, int whence)
+{
+	switch (whence) {
+	case SEEK_SET:
+	case SEEK_CUR:
+	case SEEK_END:
+		return generic_file_llseek(file, offset, whence);
+	case SEEK_DATA:
+		return bch_seek_data(file, offset);
+	case SEEK_HOLE:
+		return bch_seek_hole(file, offset);
+	}
+
+	return -EINVAL;
+}