xfs: prevent deadlock in xfs_qm_shake()

It's possible to recurse into filesystem from the memory
allocation, which deadlocks in xfs_qm_shake(). Add check
for __GFP_FS, and bail out if it is not set.

Signed-off-by: Felix Blyakher <[email protected]>
Signed-off-by: Hedi Berriche <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Andi Kleen <[email protected]>
Signed-off-by: Felix Blyakher <[email protected]>

fs/xfs/linux-2.6/kmem.h

@@ -103,7 +103,7 @@ extern void *kmem_zone_zalloc(kmem_zone_t *, unsigned int __nocast);
 static inline int
 kmem_shake_allow(gfp_t gfp_mask)
 {
-	return (gfp_mask & __GFP_WAIT) != 0;
+	return ((gfp_mask & __GFP_WAIT) && (gfp_mask & __GFP_FS));
 }
 
 #endif /* __XFS_SUPPORT_KMEM_H__ */