diff options
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/extent_io.c | 182 | ||||
| -rw-r--r-- | fs/btrfs/ordered-data.c | 23 | ||||
| -rw-r--r-- | fs/btrfs/ordered-data.h | 8 |
3 files changed, 205 insertions, 8 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index bdf75435b5f9..bfc1882ac439 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1075,6 +1075,184 @@ static int btrfs_do_readpage(struct folio *folio, struct extent_map **em_cached, return 0; } +/* + * Check if we can skip waiting the @ordered extent covering the block at @fileoff. + * + * @fileoff: Both input and output. + * Input as the file offset where the check should start at. + * Output as where the next check should start at, + * if the function returns true. + * + * Return true if we can skip to @fileoff. The caller needs to check the new + * @fileoff value to make sure it covers the full range, before skipping the + * full OE. + * + * Return false if we must wait for the ordered extent. + */ +static bool can_skip_one_ordered_range(struct btrfs_inode *inode, + struct btrfs_ordered_extent *ordered, + u64 *fileoff) +{ + const struct btrfs_fs_info *fs_info = inode->root->fs_info; + struct folio *folio; + const u32 blocksize = fs_info->sectorsize; + u64 cur = *fileoff; + bool ret; + + folio = filemap_get_folio(inode->vfs_inode.i_mapping, cur >> PAGE_SHIFT); + + /* + * We should have locked the folio(s) for range [start, end], thus + * there must be a folio and it must be locked. + */ + ASSERT(!IS_ERR(folio)); + ASSERT(folio_test_locked(folio)); + + /* + * There are several cases for the folio and OE combination: + * + * 1) Folio has no private flag + * The OE has all its IO done but not yet finished, and folio got + * invalidated. + * + * Have we have to wait for the OE to finish, as it may contain the + * to-be-inserted data checksum. + * Without the data checksum inserted into the csum tree, read will + * just fail with missing csum. + */ + if (!folio_test_private(folio)) { + ret = false; + goto out; + } + + /* + * 2) The first block is DIRTY. + * + * This means the OE is created by some other folios whose file pos is + * before this one. And since we are holding the folio lock, the writeback + * of this folio cannot start. + * + * We must skip the whole OE, because it will never start until we + * finished our folio read and unlocked the folio. + */ + if (btrfs_folio_test_dirty(fs_info, folio, cur, blocksize)) { + u64 range_len = min(folio_pos(folio) + folio_size(folio), + ordered->file_offset + ordered->num_bytes) - cur; + + ret = true; + /* + * At least inside the folio, all the remaining blocks should + * also be dirty. + */ + ASSERT(btrfs_folio_test_dirty(fs_info, folio, cur, range_len)); + *fileoff = ordered->file_offset + ordered->num_bytes; + goto out; + } + + /* + * 3) The first block is uptodate. + * + * At least the first block can be skipped, but we are still not fully + * sure. E.g. if the OE has some other folios in the range that cannot + * be skipped. + * So we return true and update @next_ret to the OE/folio boundary. + */ + if (btrfs_folio_test_uptodate(fs_info, folio, cur, blocksize)) { + u64 range_len = min(folio_pos(folio) + folio_size(folio), + ordered->file_offset + ordered->num_bytes) - cur; + + /* + * The whole range to the OE end or folio boundary should also + * be uptodate. + */ + ASSERT(btrfs_folio_test_uptodate(fs_info, folio, cur, range_len)); + ret = true; + *fileoff = cur + range_len; + goto out; + } + + /* + * 4) The first block is not uptodate. + * + * This means the folio is invalidated after the writeback was finished, + * but by some other operations (e.g. block aligned buffered write) the + * folio is inserted into filemap. + * Very much the same as case 1). + */ + ret = false; +out: + folio_put(folio); + return ret; +} + +static bool can_skip_ordered_extent(struct btrfs_inode *inode, + struct btrfs_ordered_extent *ordered, + u64 start, u64 end) +{ + const u64 range_end = min(end, ordered->file_offset + ordered->num_bytes - 1); + u64 cur = max(start, ordered->file_offset); + + while (cur < range_end) { + bool can_skip; + + can_skip = can_skip_one_ordered_range(inode, ordered, &cur); + if (!can_skip) + return false; + } + return true; +} + +/* + * Locking helper to make sure we get a stable view of extent maps for the + * involved range. + * + * This is for folio read paths (read and readahead), thus the involved range + * should have all the folios locked. + */ +static void lock_extents_for_read(struct btrfs_inode *inode, u64 start, u64 end, + struct extent_state **cached_state) +{ + u64 cur_pos; + + /* Caller must provide a valid @cached_state. */ + ASSERT(cached_state); + + /* The range must at least be page aligned, as all read paths are folio based. */ + ASSERT(IS_ALIGNED(start, PAGE_SIZE)); + ASSERT(IS_ALIGNED(end + 1, PAGE_SIZE)); + +again: + lock_extent(&inode->io_tree, start, end, cached_state); + cur_pos = start; + while (cur_pos < end) { + struct btrfs_ordered_extent *ordered; + + ordered = btrfs_lookup_ordered_range(inode, cur_pos, + end - cur_pos + 1); + /* + * No ordered extents in the range, and we hold the extent lock, + * no one can modify the extent maps in the range, we're safe to return. + */ + if (!ordered) + break; + + /* Check if we can skip waiting for the whole OE. */ + if (can_skip_ordered_extent(inode, ordered, start, end)) { + cur_pos = min(ordered->file_offset + ordered->num_bytes, + end + 1); + btrfs_put_ordered_extent(ordered); + continue; + } + + /* Now wait for the OE to finish. */ + unlock_extent(&inode->io_tree, start, end, cached_state); + btrfs_start_ordered_extent_nowriteback(ordered, start, end + 1 - start); + btrfs_put_ordered_extent(ordered); + /* We have unlocked the whole range, restart from the beginning. */ + goto again; + } +} + int btrfs_read_folio(struct file *file, struct folio *folio) { struct btrfs_inode *inode = folio_to_inode(folio); @@ -1085,7 +1263,7 @@ int btrfs_read_folio(struct file *file, struct folio *folio) struct extent_map *em_cached = NULL; int ret; - btrfs_lock_and_flush_ordered_range(inode, start, end, &cached_state); + lock_extents_for_read(inode, start, end, &cached_state); ret = btrfs_do_readpage(folio, &em_cached, &bio_ctrl, NULL); unlock_extent(&inode->io_tree, start, end, &cached_state); @@ -2370,7 +2548,7 @@ void btrfs_readahead(struct readahead_control *rac) struct extent_map *em_cached = NULL; u64 prev_em_start = (u64)-1; - btrfs_lock_and_flush_ordered_range(inode, start, end, &cached_state); + lock_extents_for_read(inode, start, end, &cached_state); while ((folio = readahead_folio(rac)) != NULL) btrfs_do_readpage(folio, &em_cached, &bio_ctrl, &prev_em_start); diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c index 4aca7475fd82..03c945711003 100644 --- a/fs/btrfs/ordered-data.c +++ b/fs/btrfs/ordered-data.c @@ -842,10 +842,12 @@ void btrfs_wait_ordered_roots(struct btrfs_fs_info *fs_info, u64 nr, /* * Start IO and wait for a given ordered extent to finish. * - * Wait on page writeback for all the pages in the extent and the IO completion - * code to insert metadata into the btree corresponding to the extent. + * Wait on page writeback for all the pages in the extent but not in + * [@nowriteback_start, @nowriteback_start + @nowriteback_len) and the + * IO completion code to insert metadata into the btree corresponding to the extent. */ -void btrfs_start_ordered_extent(struct btrfs_ordered_extent *entry) +void btrfs_start_ordered_extent_nowriteback(struct btrfs_ordered_extent *entry, + u64 nowriteback_start, u32 nowriteback_len) { u64 start = entry->file_offset; u64 end = start + entry->num_bytes - 1; @@ -865,8 +867,19 @@ void btrfs_start_ordered_extent(struct btrfs_ordered_extent *entry) * start IO on any dirty ones so the wait doesn't stall waiting * for the flusher thread to find them */ - if (!test_bit(BTRFS_ORDERED_DIRECT, &entry->flags)) - filemap_fdatawrite_range(inode->vfs_inode.i_mapping, start, end); + if (!test_bit(BTRFS_ORDERED_DIRECT, &entry->flags)) { + if (!nowriteback_len) { + filemap_fdatawrite_range(inode->vfs_inode.i_mapping, start, end); + } else { + if (start < nowriteback_start) + filemap_fdatawrite_range(inode->vfs_inode.i_mapping, start, + nowriteback_start - 1); + if (nowriteback_start + nowriteback_len < end) + filemap_fdatawrite_range(inode->vfs_inode.i_mapping, + nowriteback_start + nowriteback_len, + end); + } + } if (!freespace_inode) btrfs_might_wait_for_event(inode->root->fs_info, btrfs_ordered_extent); diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h index be36083297a7..1e6b0b182b29 100644 --- a/fs/btrfs/ordered-data.h +++ b/fs/btrfs/ordered-data.h @@ -192,7 +192,13 @@ void btrfs_add_ordered_sum(struct btrfs_ordered_extent *entry, struct btrfs_ordered_sum *sum); struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct btrfs_inode *inode, u64 file_offset); -void btrfs_start_ordered_extent(struct btrfs_ordered_extent *entry); +void btrfs_start_ordered_extent_nowriteback(struct btrfs_ordered_extent *entry, + u64 nowriteback_start, u32 nowriteback_len); +static inline void btrfs_start_ordered_extent(struct btrfs_ordered_extent *entry) +{ + return btrfs_start_ordered_extent_nowriteback(entry, 0, 0); +} + int btrfs_wait_ordered_range(struct btrfs_inode *inode, u64 start, u64 len); struct btrfs_ordered_extent * btrfs_lookup_first_ordered_extent(struct btrfs_inode *inode, u64 file_offset); |