| Message ID | 20240801163057.3981192-3-john.g.garry@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | forcealign for xfs | expand |
On 01/08/2024 17:30, John Garry wrote: > From: Dave Chinner <dchinner@redhat.com> > > When we do a large allocation, the core free space allocation code > assumes that args->maxlen is aligned to args->prod/args->mod. hence > if we get a maximum sized extent allocated, it does not do tail > alignment of the extent. > > However, this assumes that nothing modifies args->maxlen between the > original allocation context setup and trimming the selected free > space extent to size. This assumption has recently been found to be > invalid - xfs_alloc_space_available() modifies args->maxlen in low > space situations - and there may be more situations we haven't yet > found like this. > > Force aligned allocation introduces the requirement that extents are > correctly tail aligned, resulting in this occasional latent > alignment failure to be reclassified from an unimportant curiousity > to a must-fix bug. > > Removing the assumption about args->maxlen allocations always being > tail aligned is trivial, and should not impact anything because > args->maxlen for inodes with extent size hints configured are > already aligned. Hence all this change does it avoid weird corner > cases that would have resulted in unaligned extent sizes by always > trimming the extent down to an aligned size. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > Reviewed-by: "Darrick J. Wong" <djwong@kernel.org> [provisional on v1 series comment] Note that I marked this as provisional, as not all questions were answered from v1: https://lore.kernel.org/linux-xfs/20240621195058.GS3058325@frogsfrogsfrogs/ I plan on sending v4 today like this, and hope to clear up any unanswered questions then. > Signed-off-by: John Garry <john.g.garry@oracle.com> > --- > fs/xfs/libxfs/xfs_alloc.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > index d559d992c6ef..bf08b9e9d9ac 100644 > --- a/fs/xfs/libxfs/xfs_alloc.c > +++ b/fs/xfs/libxfs/xfs_alloc.c > @@ -433,20 +433,18 @@ xfs_alloc_compute_diff( > * Fix up the length, based on mod and prod. > * len should be k * prod + mod for some k. > * If len is too small it is returned unchanged. > - * If len hits maxlen it is left alone. > */ > -STATIC void > +static void > xfs_alloc_fix_len( > - xfs_alloc_arg_t *args) /* allocation argument structure */ > + struct xfs_alloc_arg *args) > { > - xfs_extlen_t k; > - xfs_extlen_t rlen; > + xfs_extlen_t k; > + xfs_extlen_t rlen = args->len; > > ASSERT(args->mod < args->prod); > - rlen = args->len; > ASSERT(rlen >= args->minlen); > ASSERT(rlen <= args->maxlen); > - if (args->prod <= 1 || rlen < args->mod || rlen == args->maxlen || > + if (args->prod <= 1 || rlen < args->mod || > (args->mod == 0 && rlen < args->prod)) > return; > k = rlen % args->prod;
diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index d559d992c6ef..bf08b9e9d9ac 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c @@ -433,20 +433,18 @@ xfs_alloc_compute_diff( * Fix up the length, based on mod and prod. * len should be k * prod + mod for some k. * If len is too small it is returned unchanged. - * If len hits maxlen it is left alone. */ -STATIC void +static void xfs_alloc_fix_len( - xfs_alloc_arg_t *args) /* allocation argument structure */ + struct xfs_alloc_arg *args) { - xfs_extlen_t k; - xfs_extlen_t rlen; + xfs_extlen_t k; + xfs_extlen_t rlen = args->len; ASSERT(args->mod < args->prod); - rlen = args->len; ASSERT(rlen >= args->minlen); ASSERT(rlen <= args->maxlen); - if (args->prod <= 1 || rlen < args->mod || rlen == args->maxlen || + if (args->prod <= 1 || rlen < args->mod || (args->mod == 0 && rlen < args->prod)) return; k = rlen % args->prod;