From: Darrick J. Wong Date: Fri, 22 Jun 2018 06:26:56 +0000 (-0700) Subject: xfs: don't trip over negative free space in xfs_reserve_blocks X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=aafe12cee0b132824f5187987f8a3fb704b9f685;p=openwrt%2Fstaging%2Fblogic.git xfs: don't trip over negative free space in xfs_reserve_blocks If we somehow end up with a filesystem that has fewer free blocks than the blocks set aside to avoid ENOSPC deadlocks, it's possible that the free space calculation in xfs_reserve_blocks will spit out a negative number (because percpu_counter_sum returns s64). We fail to notice this negative number and set fdblks_delta to it. Now we increment fdblocks(!) and the unsigned type of m_resblks means that we end up setting a ridiculously huge m_resblks reservation. Avoid this comedy of errors by detecting the negative free space and returning -ENOSPC. Signed-off-by: Darrick J. Wong Reviewed-by: Allison Henderson Reviewed-by: Christoph Hellwig --- diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c index a7afcad6b711..3f2bd6032cf8 100644 --- a/fs/xfs/xfs_fsops.c +++ b/fs/xfs/xfs_fsops.c @@ -387,7 +387,7 @@ xfs_reserve_blocks( do { free = percpu_counter_sum(&mp->m_fdblocks) - mp->m_alloc_set_aside; - if (!free) + if (free <= 0) break; delta = request - mp->m_resblks;