diff options
| author | Kent Overstreet <kent.overstreet@linux.dev> | 2025-05-14 21:32:40 -0400 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2025-05-19 08:28:41 -0400 |
| commit | cbed8287e5789558cf947a7b4d47fdf3e25c29bf (patch) | |
| tree | 8bea593146de8fd79ba66a690665aebcd3f9b15a | |
| parent | 494d458cfa70d8c107de5a6b6fc941f31c886b12 (diff) | |
bcachefs: mkwrite() now only dirties one page
Don't dirty the whole folio - fixes write amplification with
applications doing mmaped writes.
https://www.reddit.com/r/bcachefs/comments/1klzcg1/incredible_amounts_of_write_amplification_when/
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
| -rw-r--r-- | fs/bcachefs/fs-io-pagecache.c | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/fs/bcachefs/fs-io-pagecache.c b/fs/bcachefs/fs-io-pagecache.c index e072900e6a5b..fbae9c1de746 100644 --- a/fs/bcachefs/fs-io-pagecache.c +++ b/fs/bcachefs/fs-io-pagecache.c @@ -605,10 +605,14 @@ vm_fault_t bch2_page_mkwrite(struct vm_fault *vmf) struct address_space *mapping = file->f_mapping; struct bch_fs *c = inode->v.i_sb->s_fs_info; struct bch2_folio_reservation res; - unsigned len; - loff_t isize; vm_fault_t ret; + loff_t file_offset = round_down(vmf->pgoff << PAGE_SHIFT, block_bytes(c)); + unsigned offset = file_offset - folio_pos(folio); + unsigned len = max(PAGE_SIZE, block_bytes(c)); + + BUG_ON(offset + len > folio_size(folio)); + bch2_folio_reservation_init(c, inode, &res); sb_start_pagefault(inode->v.i_sb); @@ -623,24 +627,24 @@ vm_fault_t bch2_page_mkwrite(struct vm_fault *vmf) bch2_pagecache_add_get(inode); folio_lock(folio); - isize = i_size_read(&inode->v); + u64 isize = i_size_read(&inode->v); - if (folio->mapping != mapping || folio_pos(folio) >= isize) { + if (folio->mapping != mapping || file_offset >= isize) { folio_unlock(folio); ret = VM_FAULT_NOPAGE; goto out; } - len = min_t(loff_t, folio_size(folio), isize - folio_pos(folio)); + len = min_t(unsigned, len, isize - file_offset); if (bch2_folio_set(c, inode_inum(inode), &folio, 1) ?: - bch2_folio_reservation_get(c, inode, folio, &res, 0, len)) { + bch2_folio_reservation_get(c, inode, folio, &res, offset, len)) { folio_unlock(folio); ret = VM_FAULT_SIGBUS; goto out; } - bch2_set_folio_dirty(c, inode, folio, &res, 0, len); + bch2_set_folio_dirty(c, inode, folio, &res, offset, len); bch2_folio_reservation_put(c, inode, &res); folio_wait_stable(folio); |