From: Christoph Hellwig Date: Wed, 3 May 2023 15:24:40 +0000 (+0200) Subject: btrfs: use per-buffer locking for extent_buffer reading X-Git-Tag: v6.6.7~2168^2~156 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d7172f52e9933b6ec9305e7fe6e829e3939dba04;p=platform%2Fkernel%2Flinux-starfive.git btrfs: use per-buffer locking for extent_buffer reading Instead of locking and unlocking every page or the extent, just add a new EXTENT_BUFFER_READING bit that mirrors EXTENT_BUFFER_WRITEBACK for synchronizing threads trying to read an extent_buffer and to wait for I/O completion. Reviewed-by: Josef Bacik Signed-off-by: Christoph Hellwig Reviewed-by: David Sterba Signed-off-by: David Sterba --- diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 40f0639..650cb68 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4049,6 +4049,7 @@ void set_extent_buffer_uptodate(struct extent_buffer *eb) static void extent_buffer_read_end_io(struct btrfs_bio *bbio) { struct extent_buffer *eb = bbio->private; + struct btrfs_fs_info *fs_info = eb->fs_info; bool uptodate = !bbio->bio.bi_status; struct bvec_iter_all iter_all; struct bio_vec *bvec; @@ -4068,26 +4069,47 @@ static void extent_buffer_read_end_io(struct btrfs_bio *bbio) } bio_for_each_segment_all(bvec, &bbio->bio, iter_all) { - end_page_read(bvec->bv_page, uptodate, eb->start + bio_offset, - bvec->bv_len); - bio_offset += bvec->bv_len; - } + u64 start = eb->start + bio_offset; + struct page *page = bvec->bv_page; + u32 len = bvec->bv_len; - if (eb->fs_info->nodesize < PAGE_SIZE) { - unlock_extent(&bbio->inode->io_tree, eb->start, - eb->start + bio_offset - 1, NULL); + if (uptodate) + btrfs_page_set_uptodate(fs_info, page, start, len); + else + btrfs_page_clear_uptodate(fs_info, page, start, len); + + bio_offset += len; } + + clear_bit(EXTENT_BUFFER_READING, &eb->bflags); + smp_mb__after_atomic(); + wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING); free_extent_buffer(eb); bio_put(&bbio->bio); } -static void __read_extent_buffer_pages(struct extent_buffer *eb, int mirror_num, - struct btrfs_tree_parent_check *check) +int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num, + struct btrfs_tree_parent_check *check) { int num_pages = num_extent_pages(eb), i; struct btrfs_bio *bbio; + if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) + return 0; + + /* + * We could have had EXTENT_BUFFER_UPTODATE cleared by the write + * operation, which could potentially still be in flight. In this case + * we simply want to return an error. + */ + if (unlikely(test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags))) + return -EIO; + + /* Someone else is already reading the buffer, just wait for it. */ + if (test_and_set_bit(EXTENT_BUFFER_READING, &eb->bflags)) + goto done; + clear_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags); eb->read_mirror = 0; check_buffer_tree_ref(eb); @@ -4108,117 +4130,15 @@ static void __read_extent_buffer_pages(struct extent_buffer *eb, int mirror_num, __bio_add_page(&bbio->bio, eb->pages[i], PAGE_SIZE, 0); } btrfs_submit_bio(bbio, mirror_num); -} - -static int read_extent_buffer_subpage(struct extent_buffer *eb, int wait, - int mirror_num, - struct btrfs_tree_parent_check *check) -{ - struct btrfs_fs_info *fs_info = eb->fs_info; - struct extent_io_tree *io_tree; - struct page *page = eb->pages[0]; - struct extent_state *cached_state = NULL; - int ret; - - ASSERT(!test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags)); - ASSERT(PagePrivate(page)); - ASSERT(check); - io_tree = &BTRFS_I(fs_info->btree_inode)->io_tree; - - if (wait == WAIT_NONE) { - if (!try_lock_extent(io_tree, eb->start, eb->start + eb->len - 1, - &cached_state)) - return -EAGAIN; - } else { - ret = lock_extent(io_tree, eb->start, eb->start + eb->len - 1, - &cached_state); - if (ret < 0) - return ret; - } - - if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) { - unlock_extent(io_tree, eb->start, eb->start + eb->len - 1, - &cached_state); - return 0; - } - - btrfs_subpage_start_reader(fs_info, page, eb->start, eb->len); - __read_extent_buffer_pages(eb, mirror_num, check); - if (wait != WAIT_COMPLETE) { - free_extent_state(cached_state); - return 0; - } - - wait_extent_bit(io_tree, eb->start, eb->start + eb->len - 1, - EXTENT_LOCKED, &cached_state); - if (!test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) - return -EIO; - return 0; -} - -int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num, - struct btrfs_tree_parent_check *check) -{ - int i; - struct page *page; - int locked_pages = 0; - int num_pages; - - if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) - return 0; - - /* - * We could have had EXTENT_BUFFER_UPTODATE cleared by the write - * operation, which could potentially still be in flight. In this case - * we simply want to return an error. - */ - if (unlikely(test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags))) - return -EIO; - - if (eb->fs_info->nodesize < PAGE_SIZE) - return read_extent_buffer_subpage(eb, wait, mirror_num, check); - - num_pages = num_extent_pages(eb); - for (i = 0; i < num_pages; i++) { - page = eb->pages[i]; - if (wait == WAIT_NONE) { - /* - * WAIT_NONE is only utilized by readahead. If we can't - * acquire the lock atomically it means either the eb - * is being read out or under modification. - * Either way the eb will be or has been cached, - * readahead can exit safely. - */ - if (!trylock_page(page)) - goto unlock_exit; - } else { - lock_page(page); - } - locked_pages++; - } - - __read_extent_buffer_pages(eb, mirror_num, check); - - if (wait != WAIT_COMPLETE) - return 0; - - for (i = 0; i < num_pages; i++) { - page = eb->pages[i]; - wait_on_page_locked(page); - if (!PageUptodate(page)) +done: + if (wait == WAIT_COMPLETE) { + wait_on_bit_io(&eb->bflags, EXTENT_BUFFER_READING, TASK_UNINTERRUPTIBLE); + if (!test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) return -EIO; } return 0; - -unlock_exit: - while (locked_pages > 0) { - locked_pages--; - page = eb->pages[locked_pages]; - unlock_page(page); - } - return 0; } static bool report_eb_range(const struct extent_buffer *eb, unsigned long start, diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h index 217c433..2d91ca9 100644 --- a/fs/btrfs/extent_io.h +++ b/fs/btrfs/extent_io.h @@ -29,6 +29,8 @@ enum { /* write IO error */ EXTENT_BUFFER_WRITE_ERR, EXTENT_BUFFER_NO_CHECK, + /* Indicate that extent buffer pages a being read */ + EXTENT_BUFFER_READING, }; /* these are flags for __process_pages_contig */