From 4a3560c4f3f0f92d3b673944753e3e947e030bc4 Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Fri, 7 Aug 2015 16:48:41 +0800 Subject: [PATCH] Btrfs: fix defrag to merge tail file extent The file layout is [extent 1]...[extent n][4k extent][HOLE][extent x] extent 1~n and 4k extent can be merged during defrag, and the whole defrag bytes is larger than our defrag thresh(256k), 4k extent as a tail is left unmerged since we check if its next extent can be merged (the next one is a hole, so the check will fail), the layout thus can be [new extent][4k extent][HOLE][extent x] (1~n) To fix it, beside looking at the next one, this also looks at the previous one by checking @defrag_end, which is set to 0 when we decide to stop merging contiguous extents, otherwise, we can merge the previous one with our extent. Also, this makes btrfs behave consistent with how xfs and ext4 do. Signed-off-by: Liu Bo Signed-off-by: Chris Mason --- fs/btrfs/ioctl.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 3e2a80433504..d1e4cac83311 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1030,6 +1030,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh, struct extent_map *em; int ret = 1; bool next_mergeable = true; + bool prev_mergeable = true; /* * make sure that once we start defragging an extent, we keep on @@ -1050,13 +1051,16 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh, goto out; } + if (!*defrag_end) + prev_mergeable = false; + next_mergeable = defrag_check_next_extent(inode, em); /* * we hit a real extent, if it is big or the next extent is not a * real extent, don't bother defragging it */ if (!compress && (*last_len == 0 || *last_len >= thresh) && - (em->len >= thresh || !next_mergeable)) + (em->len >= thresh || (!next_mergeable && !prev_mergeable))) ret = 0; out: /* -- 2.20.1