From 51f395ad4058883e4273b02fdebe98072dbdc0d2 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Fri, 8 Aug 2014 13:06:20 +0800 Subject: [PATCH] btrfs: Use right extent length when inserting overlap extent map. When current btrfs finds that a new extent map is going to be insereted but failed with -EEXIST, it will try again to insert the extent map but with the length of sectorsize. This is OK if we don't enable 'no-holes' feature since all extent space is continuous, we will not go into the not found->insert routine. But if we enable 'no-holes' feature, it will make things out of control. e.g. in 4K sectorsize, we pass the following args to btrfs_get_extent(): btrfs_get_extent() args: start: 27874 len 4100 28672 27874 28672 27874+4100 32768 |-----------------------| |---------hole--------------------|---------data----------| 1) not found and insert Since no extent map containing the range, btrfs_get_extent() will go into the not_found and insert routine, which will try to insert the extent map (27874, 27847 + 4100). 2) first overlap But it overlaps with (28672, 32768) extent, so -EEXIST will be returned by add_extent_mapping(). 3) retry but still overlap After catching the -EEXIST, then btrfs_get_extent() will try insert it again but with 4K length, which still overlaps, so -EEXIST will be returned. This makes the following patch fail to punch hole. d77815461f047e561f77a07754ae923ade597d4e btrfs: Avoid trucating page or punching hole in a already existed hole. This patch will use the right length, which is the (exsisting->start - em->start) to insert, making the above patch works in 'no-holes' mode. Also, some small code style problems in above patch is fixed too. Reported-by: Filipe David Manana Signed-off-by: Qu Wenruo Reviewed-by: Filipe David Manana Tested-by: Filipe David Manana Signed-off-by: Chris Mason --- fs/btrfs/file.c | 4 ++-- fs/btrfs/inode.c | 7 +++---- 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 77e33534c7d6..f15c13f97018 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2215,7 +2215,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len) goto out_only_mutex; } - lockstart = round_up(offset , BTRFS_I(inode)->root->sectorsize); + lockstart = round_up(offset, BTRFS_I(inode)->root->sectorsize); lockend = round_down(offset + len, BTRFS_I(inode)->root->sectorsize) - 1; same_page = ((offset >> PAGE_CACHE_SHIFT) == @@ -2276,7 +2276,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len) tail_start + tail_len, 0, 1); if (ret) goto out_only_mutex; - } + } } } diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 2ac260d41ccd..ae98df67950f 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -6146,14 +6146,14 @@ out_fail: static int merge_extent_mapping(struct extent_map_tree *em_tree, struct extent_map *existing, struct extent_map *em, - u64 map_start, u64 map_len) + u64 map_start) { u64 start_diff; BUG_ON(map_start < em->start || map_start >= extent_map_end(em)); start_diff = map_start - em->start; em->start = map_start; - em->len = map_len; + em->len = existing->start - em->start; if (em->block_start < EXTENT_MAP_LAST_BYTE && !test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) { em->block_start += start_diff; @@ -6441,8 +6441,7 @@ insert: em->len); if (existing) { err = merge_extent_mapping(em_tree, existing, - em, start, - root->sectorsize); + em, start); free_extent_map(existing); if (err) { free_extent_map(em);