From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
In xfs_bmap_btalloc, we try using the CoW extent size hint to force
allocations to align (offset-wise) to cowextsz granularity to reduce CoW
fragmentation. This works fine until we cannot satisfy the allocation
with enough blocks to cover the requested range and the alignment hints.
If this happens, return an unaligned region because if we don't the
extent trim functions cause us to return a zero-length extent to iomap,
which iomap doesn't catch and thus blows up.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/iomap.c | 2 +-
fs/xfs/libxfs/xfs_bmap.c | 21 +++++++++++++++++++--
2 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/fs/iomap.c b/fs/iomap.c
index e5de772..aec35a0 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -63,7 +63,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
if (ret)
return ret;
- if (WARN_ON(iomap.offset > pos))
+ if (WARN_ON(iomap.offset > pos) || WARN_ON(iomap.length == 0))
return -EIO;
/*
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 93ce2c6..4ec1fdc5 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3480,8 +3480,20 @@ xfs_bmap_btalloc_filestreams(
static void
xfs_bmap_btalloc_cow(
struct xfs_bmalloca *ap,
- struct xfs_alloc_arg *args)
+ struct xfs_alloc_arg *args,
+ xfs_fileoff_t orig_offset,
+ xfs_extlen_t orig_length)
{
+ /*
+ * If we didn't get enough blocks to satisfy the cowextsize
+ * aligned request, break the alignment and return whatever we
+ * got; it's the best we can do.
+ */
+ if (ap->length <= orig_length)
+ ap->offset = orig_offset;
+ else if (ap->offset + ap->length < orig_offset + orig_length)
+ ap->offset = orig_offset + orig_length - ap->length;
+
/* Filling a previously reserved extent; nothing to do here. */
if (ap->wasdel)
return;
@@ -3520,6 +3532,8 @@ xfs_bmap_btalloc(
xfs_agnumber_t fb_agno; /* ag number of ap->firstblock */
xfs_agnumber_t ag;
xfs_alloc_arg_t args;
+ xfs_fileoff_t orig_offset;
+ xfs_extlen_t orig_length;
xfs_extlen_t blen;
xfs_extlen_t nextminlen = 0;
int nullfb; /* true if ap->firstblock isn't set */
@@ -3529,6 +3543,8 @@ xfs_bmap_btalloc(
int stripe_align;
ASSERT(ap->length);
+ orig_offset = ap->offset;
+ orig_length = ap->length;
mp = ap->ip->i_mount;
@@ -3745,7 +3761,8 @@ xfs_bmap_btalloc(
ASSERT(nullfb || fb_agno <= args.agno);
ap->length = args.len;
if (ap->flags & XFS_BMAPI_COWFORK) {
- xfs_bmap_btalloc_cow(ap, &args);
+ xfs_bmap_btalloc_cow(ap, &args, orig_offset,
+ orig_length);
} else {
ap->ip->i_d.di_nblocks += args.len;
xfs_trans_log_inode(ap->tp, ap->ip, XFS_ILOG_CORE);
--
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