[14/50] JFFS2: fix write deadlock regression

From: Greg KH
Date: Mon Sep 24 2007 - 12:29:53 EST

From: Jason Lunz <lunz@xxxxxxxxxxxx>

Changeset fc0e01974ccccc7530b7634a63ee3fcc57b845ea from mainline.

I've bisected the deadlock when many small appends are done on jffs2 down to
this commit:

commit 6fe6900e1e5b6fa9e5c59aa5061f244fe3f467e2
Author: Nick Piggin <npiggin@xxxxxxx>
Date: Sun May 6 14:49:04 2007 -0700

mm: make read_cache_page synchronous

Ensure pages are uptodate after returning from read_cache_page, which allows
us to cut out most of the filesystem-internal PageUptodate calls.

I didn't have a great look down the call chains, but this appears to fixes 7
possible use-before uptodate in hfs, 2 in hfsplus, 1 in jfs, a few in
ecryptfs, 1 in jffs2, and a possible cleared data overwritten with readpage in
block2mtd. All depending on whether the filler is async and/or can return
with a !uptodate page.

It introduced a wait to read_cache_page, as well as a
read_cache_page_async function equivalent to the old read_cache_page
without any callers.

Switching jffs2_gc_fetch_page to read_cache_page_async for the old
behavior makes the deadlocks go away, but maybe reintroduces the
use-before-uptodate problem? I don't understand the mm/fs interaction
well enough to say.

[It's fine. dwmw2.]

Signed-off-by: Jason Lunz <lunz@xxxxxxxxxxxx>
Signed-off-by: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

fs/jffs2/fs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -627,7 +627,7 @@ unsigned char *jffs2_gc_fetch_page(struc
struct inode *inode = OFNI_EDONI_2SFFJ(f);
struct page *pg;

- pg = read_cache_page(inode->i_mapping, offset >> PAGE_CACHE_SHIFT,
+ pg = read_cache_page_async(inode->i_mapping, offset >> PAGE_CACHE_SHIFT,
(void *)jffs2_do_readpage_unlock, inode);
if (IS_ERR(pg))
return (void *)pg;

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