From e9eec72151e215c9bc58431c1a7e00e759c6c391 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Fri, 6 Aug 2021 16:12:38 +0800 Subject: [PATCH] btrfs: defrag: introduce helper to defrag a range A new helper, defrag_one_range(), is introduced to defrag one range. This function will mostly prepare the needed pages and extent status for defrag_one_locked_target(). As we can only have a consistent view of extent map with page and extent bits locked, we need to re-check the range passed in to get a real target list for defrag_one_locked_target(). Since defrag_collect_targets() will call defrag_lookup_extent() and lock extent range, we also need to teach those two functions to skip extent lock. Thus new parameter, @locked, is introduced to skip extent lock if the caller has already locked the range. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/ioctl.c | 103 ++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 93 insertions(+), 10 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 465ee00e2954..d05db6ce559c 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1087,7 +1087,8 @@ none: return -ENOENT; } -static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start) +static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start, + bool locked) { struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree; struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; @@ -1107,9 +1108,11 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start) u64 end = start + sectorsize - 1; /* get the big lock and read metadata off disk */ - lock_extent_bits(io_tree, start, end, &cached); + if (!locked) + lock_extent_bits(io_tree, start, end, &cached); em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, sectorsize); - unlock_extent_cached(io_tree, start, end, &cached); + if (!locked) + unlock_extent_cached(io_tree, start, end, &cached); if (IS_ERR(em)) return NULL; @@ -1118,7 +1121,8 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start) return em; } -static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em) +static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em, + bool locked) { struct extent_map *next; bool ret = true; @@ -1127,7 +1131,7 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em) if (em->start + em->len >= i_size_read(inode)) return false; - next = defrag_lookup_extent(inode, em->start + em->len); + next = defrag_lookup_extent(inode, em->start + em->len, locked); if (!next || next->block_start >= EXTENT_MAP_LAST_BYTE) ret = false; else if ((em->block_start + em->block_len == next->block_start) && @@ -1156,7 +1160,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh, *skip = 0; - em = defrag_lookup_extent(inode, start); + em = defrag_lookup_extent(inode, start, false); if (!em) return 0; @@ -1169,7 +1173,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh, if (!*defrag_end) prev_mergeable = false; - next_mergeable = defrag_check_next_extent(inode, em); + next_mergeable = defrag_check_next_extent(inode, em, false); /* * we hit a real extent, if it is big or the next extent is not a * real extent, don't bother defragging it @@ -1449,12 +1453,13 @@ struct defrag_target_range { * @do_compress: whether the defrag is doing compression * if true, @extent_thresh will be ignored and all regular * file extents meeting @newer_than will be targets. + * @locked: if the range has already held extent lock * @target_list: list of targets file extents */ static int defrag_collect_targets(struct btrfs_inode *inode, u64 start, u64 len, u32 extent_thresh, u64 newer_than, bool do_compress, - struct list_head *target_list) + bool locked, struct list_head *target_list) { u64 cur = start; int ret = 0; @@ -1465,7 +1470,7 @@ static int defrag_collect_targets(struct btrfs_inode *inode, bool next_mergeable = true; u64 range_len; - em = defrag_lookup_extent(&inode->vfs_inode, cur); + em = defrag_lookup_extent(&inode->vfs_inode, cur, locked); if (!em) break; @@ -1489,7 +1494,8 @@ static int defrag_collect_targets(struct btrfs_inode *inode, if (em->len >= extent_thresh) goto next; - next_mergeable = defrag_check_next_extent(&inode->vfs_inode, em); + next_mergeable = defrag_check_next_extent(&inode->vfs_inode, em, + locked); if (!next_mergeable) { struct defrag_target_range *last; @@ -1606,6 +1612,83 @@ static int defrag_one_locked_target(struct btrfs_inode *inode, return ret; } +static int defrag_one_range(struct btrfs_inode *inode, u64 start, u32 len, + u32 extent_thresh, u64 newer_than, bool do_compress) +{ + struct extent_state *cached_state = NULL; + struct defrag_target_range *entry; + struct defrag_target_range *tmp; + LIST_HEAD(target_list); + struct page **pages; + const u32 sectorsize = inode->root->fs_info->sectorsize; + u64 last_index = (start + len - 1) >> PAGE_SHIFT; + u64 start_index = start >> PAGE_SHIFT; + unsigned int nr_pages = last_index - start_index + 1; + int ret = 0; + int i; + + ASSERT(nr_pages <= CLUSTER_SIZE / PAGE_SIZE); + ASSERT(IS_ALIGNED(start, sectorsize) && IS_ALIGNED(len, sectorsize)); + + pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); + if (!pages) + return -ENOMEM; + + /* Prepare all pages */ + for (i = 0; i < nr_pages; i++) { + pages[i] = defrag_prepare_one_page(inode, start_index + i); + if (IS_ERR(pages[i])) { + ret = PTR_ERR(pages[i]); + pages[i] = NULL; + goto free_pages; + } + } + for (i = 0; i < nr_pages; i++) + wait_on_page_writeback(pages[i]); + + /* Lock the pages range */ + lock_extent_bits(&inode->io_tree, start_index << PAGE_SHIFT, + (last_index << PAGE_SHIFT) + PAGE_SIZE - 1, + &cached_state); + /* + * Now we have a consistent view about the extent map, re-check + * which range really needs to be defragged. + * + * And this time we have extent locked already, pass @locked = true + * so that we won't relock the extent range and cause deadlock. + */ + ret = defrag_collect_targets(inode, start, len, extent_thresh, + newer_than, do_compress, true, + &target_list); + if (ret < 0) + goto unlock_extent; + + list_for_each_entry(entry, &target_list, list) { + ret = defrag_one_locked_target(inode, entry, pages, nr_pages, + &cached_state); + if (ret < 0) + break; + } + + list_for_each_entry_safe(entry, tmp, &target_list, list) { + list_del_init(&entry->list); + kfree(entry); + } +unlock_extent: + unlock_extent_cached(&inode->io_tree, start_index << PAGE_SHIFT, + (last_index << PAGE_SHIFT) + PAGE_SIZE - 1, + &cached_state); +free_pages: + for (i = 0; i < nr_pages; i++) { + if (pages[i]) { + unlock_page(pages[i]); + put_page(pages[i]); + } + } + kfree(pages); + return ret; +} + /* * Entry point to file defragmentation. *