Commit 2fe33661 authored Aug 24, 2010 by Stuart Brodsky Committed by Dave Chinner Aug 24, 2010

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>

parent efceab1d

fs/xfs/linux-2.6/xfs_super.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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) \|\|