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author | Hugh Dickins <hughd@google.com> | 2012-11-16 14:15:04 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-11-16 14:33:04 -0800 |
commit | 0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66 (patch) | |
tree | bfd85ce2e0fede607ad196258d8071c67897d9eb | |
parent | 215c02bc33bbd5ff4d7379a909462d11f0103218 (diff) | |
download | linux-3.10-0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66.tar.gz linux-3.10-0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66.tar.bz2 linux-3.10-0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66.zip |
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>
-rw-r--r-- | mm/shmem.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index dc12264f44f..89341b658bd 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -643,7 +643,7 @@ static void shmem_evict_inode(struct inode *inode) kfree(info->symlink); simple_xattrs_free(&info->xattrs); - BUG_ON(inode->i_blocks); + WARN_ON(inode->i_blocks); shmem_free_inode(inode->i_sb); clear_inode(inode); } |