Writing a xfstests case for this, will come soon. Thanks, -liubo On Fri, Aug 07, 2015 at 04:48:41PM +0800, Liu Bo wrote: > 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 <bo.li.liu@xxxxxxxxxx> > --- > 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 0770c91..0691b2b 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: > /* > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
