This is a note to let you know that I've just added the patch titled
tmpfs: change final i_blocks BUG to WARNING
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tmpfs-change-final-i_blocks-bug-to-warning.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <[email protected]>
Date: Fri, 16 Nov 2012 14:15:04 -0800
Subject: tmpfs: change final i_blocks BUG to WARNING
From: Hugh Dickins <[email protected]>
commit 0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66 upstream.
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 <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/shmem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -595,7 +595,7 @@ static void shmem_evict_inode(struct ino
kfree(xattr->name);
kfree(xattr);
}
- BUG_ON(inode->i_blocks);
+ WARN_ON(inode->i_blocks);
shmem_free_inode(inode->i_sb);
end_writeback(inode);
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.4/tmpfs-change-final-i_blocks-bug-to-warning.patch
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