From: Dave Chinner dchinner@redhat.com

maillist inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9VTE3 CVE: NA

Reference: https://lore.kernel.org/linux-xfs/20240705162450.3481169-1-john.g.garry@orac...

--------------------------------

When we are near ENOSPC and don't have enough free space for an args->maxlen allocation, xfs_alloc_space_available() will trim args->maxlen to equal the available space. However, this function has only checked that there is enough contiguous free space for an aligned args->minlen allocation to succeed. Hence there is no guarantee that an args->maxlen allocation will succeed, nor that the available space will allow for correct alignment of an args->maxlen allocation.

Further, by trimming args->maxlen arbitrarily, it breaks an assumption made in xfs_alloc_fix_len() that if the caller wants aligned allocation, then args->maxlen will be set to an aligned value. It then skips the tail alignment and so we end up with extents that aren't aligned to extent size hint boundaries as we approach ENOSPC.

To avoid this problem, don't reduce args->maxlen by some random, arbitrary amount. If args->maxlen is too large for the available space, reduce the allocation to a minlen allocation as we know we have contiguous free space available for this to succeed and always be correctly aligned.

Signed-off-by: Dave Chinner dchinner@redhat.com Signed-off-by: John Garry john.g.garry@oracle.com Signed-off-by: Long Li leo.lilong@huawei.com --- fs/xfs/libxfs/xfs_alloc.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index 95bfe89651ad..19d89bf19b48 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c @@ -2385,14 +2385,23 @@ xfs_alloc_space_available( if (available < (int)max(args->total, alloc_len)) return false;

+ if (flags & XFS_ALLOC_FLAG_CHECK) + return true; + /* - * Clamp maxlen to the amount of free space available for the actual - * extent allocation. + * If we can't do a maxlen allocation, then we must reduce the size of + * the allocation to match the available free space. We know how big + * the largest contiguous free space we can allocate is, so that's our + * upper bound. However, we don't exaclty know what alignment/size + * constraints have been placed on the allocation, so we can't + * arbitrarily select some new max size. Hence make this a minlen + * allocation as we know that will definitely succeed and match the + * callers alignment constraints. */ - if (available < (int)args->maxlen && !(flags & XFS_ALLOC_FLAG_CHECK)) { - args->maxlen = available; + alloc_len = args->maxlen + (args->alignment - 1) + args->minalignslop; + if (longest < alloc_len) { + args->maxlen = args->minlen; ASSERT(args->maxlen > 0); - ASSERT(args->maxlen >= args->minlen); }

return true;

From: Dave Chinner dchinner@redhat.com

maillist inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9VTE3 CVE: NA

Reference: https://lore.kernel.org/linux-xfs/20240705162450.3481169-1-john.g.garry@orac...

--------------------------------

If args->minlen is not aligned to the constraints of forced alignment, we may do minlen allocations that are not aligned when we approach ENOSPC. Avoid this by always aligning args->minlen appropriately. If alignment of minlen results in a value smaller than the alignment constraint, fail the allocation immediately.

Signed-off-by: Dave Chinner dchinner@redhat.com Reviewed-by: "Darrick J. Wong" djwong@kernel.org Signed-off-by: John Garry john.g.garry@oracle.com Conflicts: fs/xfs/libxfs/xfs_bmap.c [Conflicts in xfs_bmap_select_minlen()] Signed-off-by: Long Li leo.lilong@huawei.com --- fs/xfs/libxfs/xfs_bmap.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c index 7682dfe2f701..1cb4fe414e55 100644 --- a/fs/xfs/libxfs/xfs_bmap.c +++ b/fs/xfs/libxfs/xfs_bmap.c @@ -3253,32 +3253,44 @@ xfs_bmap_longest_free_extent( return error; }

-static void +static int xfs_bmap_select_minlen( struct xfs_bmalloca *ap, struct xfs_alloc_arg *args, xfs_extlen_t *blen, int notinit) { + xfs_extlen_t nlen = 0; + if (notinit || *blen < ap->minlen) { /* * Since we did a BUF_TRYLOCK above, it is possible that * there is space for this request. */ - args->minlen = ap->minlen; + nlen = ap->minlen; } else if (*blen < args->maxlen) { /* * If the best seen length is less than the request length, * use the best as the minimum. */ - args->minlen = *blen; + + nlen = *blen; } else { /* * Otherwise we've seen an extent as big as maxlen, use that * as the minimum. */ - args->minlen = args->maxlen; + nlen = args->maxlen; } + + if (args->alignment > 1) { + nlen = rounddown(nlen, args->alignment); + if (nlen < ap->minlen) { + return -ENOSPC; + } + } + args->minlen = nlen; + return 0; }

STATIC int @@ -3311,8 +3323,8 @@ xfs_bmap_btalloc_nullfb( break; }

- xfs_bmap_select_minlen(ap, args, blen, notinit); - return 0; + error = xfs_bmap_select_minlen(ap, args, blen, notinit); + return error; }

STATIC int @@ -3349,7 +3361,9 @@ xfs_bmap_btalloc_filestreams(

}

- xfs_bmap_select_minlen(ap, args, blen, notinit); + error = xfs_bmap_select_minlen(ap, args, blen, notinit); + if (error) + return error;

/* * Set the failure fallback case to look in the selected AG as stream