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btrfs: avoid overflowing f_bfree

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Since mixed block groups accounting isn't byte-accurate and f_bree is an
unsigned integer, it could overflow. Avoid this.

Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Suggested-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Luis de Bethencourt 2016-03-30 23:18:14 +01:00 committed by David Sterba
parent ae02d1bd07
commit 41b34accb2
1 changed files with 5 additions and 1 deletions
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6
fs/btrfs/super.c
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@ -2100,7 +2100,11 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
/* Account global block reserve as used, it's in logical size already */
spin_lock(&block_rsv->lock);
buf->f_bfree -= block_rsv->size >> bits;
/* Mixed block groups accounting is not byte-accurate, avoid overflow */
if (buf->f_bfree >= block_rsv->size >> bits)
buf->f_bfree -= block_rsv->size >> bits;
else
buf->f_bfree = 0;
spin_unlock(&block_rsv->lock);
buf->f_bavail = div_u64(total_free_data, factor);