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authorStuart Brodsky <sbrodsky@sgi.com>2010-08-24 11:46:05 +1000
committerDave Chinner <david@fromorbit.com>2010-08-24 11:46:05 +1000
commit2fe33661fcd79d4c53022509f7223d526b5fa233 (patch)
tree1c26f0ca23372dc7142fa4f9395056c529378801
parentefceab1d563153a2b1a6e7d35376241a48126989 (diff)
xfs: ensure f_ffree returned by statfs() is non-negative
Because of delayed updates to sb_icount field in the super block, it is possible to allocate over maxicount number of inodes. This causes the arithmetic to calculate a negative number of free inodes in user commands like df or stat -f. Since maxicount is a somewhat arbitrary number, a slight over allocation is not critical but user commands should be displayed as 0 or greater and never go negative. To do this the value in the stats buffer f_ffree is capped to never go negative. [ Modified to use max_t as per Christoph's comment. ] Signed-off-by: Stu Brodsky <sbrodsky@sgi.com> Signed-off-by: Dave Chinner <dchinner@redhat.com>
-rw-r--r--fs/xfs/linux-2.6/xfs_super.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 15c35b62ff14..c6b24e7c308a 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -1226,6 +1226,7 @@ xfs_fs_statfs(
struct xfs_inode *ip = XFS_I(dentry->d_inode);
__uint64_t fakeinos, id;
xfs_extlen_t lsize;
+ __int64_t ffree;
statp->f_type = XFS_SB_MAGIC;
statp->f_namelen = MAXNAMELEN - 1;
@@ -1249,7 +1250,11 @@ xfs_fs_statfs(
statp->f_files = min_t(typeof(statp->f_files),
statp->f_files,
mp->m_maxicount);
- statp->f_ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);
+
+ /* make sure statp->f_ffree does not underflow */
+ ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);
+ statp->f_ffree = max_t(__int64_t, ffree, 0);
+
spin_unlock(&mp->m_sb_lock);
if ((ip->i_d.di_flags & XFS_DIFLAG_PROJINHERIT) ||