xfs_set_maxicount() overflowed fairly easily for large filesystems
and large maxicount; we started out by multiplying dblocks by
the percentage, *then* dividing by 100, and never checked for
an overflow. The calculations were also, IMHO, a little hard
to follow.
I rewrote it using mult_frac (so handy!) and rounddown, to
do a nice no-overflow, no-precision-loss multiplication by
(%/100), then round down to the inode allocation unit.
Then check to see if we've overflowed the u64, and set to
XFS_MAXINUMBER if so.
Also, growfs open-coded the setting of maxicount; call the
handy helper instead.
This slightly changes growfs behavior, because we weren't
rounding to the allocation multiple in that code. I checked
that we get the same answers for non-growfs cases by running
100 mkfs.xfs's with imaxpct from 1 to 100, and it gives the
same inode count in all cases.
Thanks to dchinner for pointing out that this could use fixing.
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---
Ok Brian, have at it. ;)
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 02fb943..867e476 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -471,12 +471,7 @@ xfs_growfs_data_private(
/* New allocation groups fully initialized, so update mount struct */
if (nagimax)
mp->m_maxagi = nagimax;
- if (mp->m_sb.sb_imax_pct) {
- __uint64_t icount = mp->m_sb.sb_dblocks * mp->m_sb.sb_imax_pct;
- do_div(icount, 100);
- mp->m_maxicount = icount << mp->m_sb.sb_inopblog;
- } else
- mp->m_maxicount = 0;
+ xfs_set_maxicount(mp);
xfs_set_low_space_thresholds(mp);
/* update secondary superblocks. */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 02df7b4..0ec2b19 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -419,24 +419,24 @@ xfs_update_alignment(xfs_mount_t *mp)
}
/*
- * Set the maximum inode count for this filesystem
+ * Set the maximum inode count for this filesystem based on sb_imax_pct
*/
-STATIC void
+void
xfs_set_maxicount(xfs_mount_t *mp)
{
xfs_sb_t *sbp = &(mp->m_sb);
- __uint64_t icount;
+ __uint64_t iblocks;
if (sbp->sb_imax_pct) {
/*
* Make sure the maximum inode count is a multiple
* of the units we allocate inodes in.
*/
- icount = sbp->sb_dblocks * sbp->sb_imax_pct;
- do_div(icount, 100);
- do_div(icount, mp->m_ialloc_blks);
- mp->m_maxicount = (icount * mp->m_ialloc_blks) <<
- sbp->sb_inopblog;
+ iblocks = mult_frac(sbp->sb_dblocks, sbp->sb_imax_pct, 100);
+ iblocks = rounddown(iblocks, mp->m_ialloc_blks);
+ mp->m_maxicount = iblocks << sbp->sb_inopblog;
+ if (mp->m_maxicount < iblocks)
+ mp->m_maxicount = XFS_MAXINUMBER;
} else {
mp->m_maxicount = 0;
}
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index a466c5e..6288a56 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -388,6 +388,7 @@ extern int xfs_mod_incore_sb_batch(xfs_mount_t *, xfs_mod_sb_t *,
extern int xfs_mount_log_sb(xfs_mount_t *, __int64_t);
extern struct xfs_buf *xfs_getsb(xfs_mount_t *, int);
extern int xfs_readsb(xfs_mount_t *, int);
+void xfs_set_maxicount(xfs_mount_t *mp);
extern void xfs_freesb(xfs_mount_t *);
extern int xfs_fs_writable(xfs_mount_t *);
extern int xfs_sb_validate_fsb_count(struct xfs_sb *, __uint64_t);
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