diff options
authorHugh Dickins <hughd@google.com>2012-11-16 14:15:04 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-11-16 14:33:04 -0800
commit0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66 (patch)
parent215c02bc33bbd5ff4d7379a909462d11f0103218 (diff)
tmpfs: change final i_blocks BUG to WARNING
Under a particular load on one machine, I have hit shmem_evict_inode()'s BUG_ON(inode->i_blocks), enough times to narrow it down to a particular race between swapout and eviction. It comes from the "if (freed > 0)" asymmetry in shmem_recalc_inode(), and the lack of coherent locking between mapping's nrpages and shmem's swapped count. There's a window in shmem_writepage(), between lowering nrpages in shmem_delete_from_page_cache() and then raising swapped count, when the freed count appears to be +1 when it should be 0, and then the asymmetry stops it from being corrected with -1 before hitting the BUG. One answer is coherent locking: using tree_lock throughout, without info->lock; reasonable, but the raw_spin_lock in percpu_counter_add() on used_blocks makes that messier than expected. Another answer may be a further effort to eliminate the weird shmem_recalc_inode() altogether, but previous attempts at that failed. So far undecided, but for now change the BUG_ON to WARN_ON: in usual circumstances it remains a useful consistency check. Signed-off-by: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index dc12264f44f5..89341b658bd0 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -643,7 +643,7 @@ static void shmem_evict_inode(struct inode *inode)
- BUG_ON(inode->i_blocks);
+ WARN_ON(inode->i_blocks);