The patch titled
mm: fix pagecache write deadlocks (comment)
has been added to the -mm tree. Its filename is
mm-fix-pagecache-write-deadlocks-comment.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: mm: fix pagecache write deadlocks (comment)
From: Nick Piggin <npiggin@xxxxxxx>
Comment was not entirely clear about why we must eliminate all other
possibilities.
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/filemap.c | 17 ++++++++++++-----
1 files changed, 12 insertions(+), 5 deletions(-)
diff -puN mm/filemap.c~mm-fix-pagecache-write-deadlocks-comment mm/filemap.c
--- a/mm/filemap.c~mm-fix-pagecache-write-deadlocks-comment
+++ a/mm/filemap.c
@@ -2155,12 +2155,19 @@ retry_noprogress:
if (!PageUptodate(page)) {
/*
* If the page is not uptodate, we cannot allow a
- * partial commit_write, because that might expose
- * uninitialised data.
+ * partial commit_write because when we unlock the
+ * page below, someone else might bring it uptodate
+ * and we lose our write. We cannot allow a full
+ * commit_write, because that exposes uninitialised
+ * data. We cannot zero the rest of the file and do
+ * a full commit_write because that exposes transient
+ * zeroes.
*
- * We will enter the single-segment path below, which
- * should get the filesystem to bring the page
- * uputodate for us next time.
+ * Abort the operation entirely with a zero length
+ * commit_write. Retry. We will enter the
+ * single-segment path below, which should get the
+ * filesystem to bring the page uputodate for us next
+ * time.
*/
if (unlikely(copied != bytes))
copied = 0;
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
mm-comment-mmap_sem--lock_page-lockorder.patch
mm-only-mm-debug-write-deadlocks.patch
mm-fix-pagecache-write-deadlocks.patch
mm-fix-pagecache-write-deadlocks-comment.patch
oom-dont-kill-unkillable-children-or-siblings.patch
oom-cleanup-messages.patch
oom-less-memdie.patch
mm-incorrect-vm_fault_oom-returns-from-drivers.patch
mm-add-arch_alloc_page.patch
radix-tree-rcu-lockless-readside.patch
-
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