The patch titled
shmem: fix BUG in shmem_writepage
has been added to the -mm tree. Its filename is
shmem-fix-bug-in-shmem_writepage.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: shmem: fix BUG in shmem_writepage
From: Miklos Szeredi <mszeredi@xxxxxxx>
BUG_ON(!entry) in shmem_writepage() is triggered in rare circumstances.
The cause is that shmem_truncate_range() erroneously removes partially
truncated directory pages at the end of the range. A later reclaim on
pages pointing to these removed directories triggers the BUG.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Badari Pulavarty <pbadari@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff -puN mm/shmem.c~shmem-fix-bug-in-shmem_writepage mm/shmem.c
--- a/mm/shmem.c~shmem-fix-bug-in-shmem_writepage
+++ a/mm/shmem.c
@@ -543,7 +543,9 @@ static void shmem_truncate_range(struct
if (*dir) {
diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
- if (!diroff && !offset) {
+ if (!diroff && !offset &&
+ (!punch_hole ||
+ limit - idx >= ENTRIES_PER_PAGEPAGE)) {
*dir = NULL;
nr_pages_to_free++;
list_add(&middir->lru, &pages_to_free);
@@ -570,9 +572,12 @@ static void shmem_truncate_range(struct
}
stage = idx + ENTRIES_PER_PAGEPAGE;
middir = *dir;
- *dir = NULL;
- nr_pages_to_free++;
- list_add(&middir->lru, &pages_to_free);
+ if (!punch_hole ||
+ limit - idx >= ENTRIES_PER_PAGEPAGE) {
+ *dir = NULL;
+ nr_pages_to_free++;
+ list_add(&middir->lru, &pages_to_free);
+ }
shmem_dir_unmap(dir);
cond_resched();
dir = shmem_dir_map(middir);
@@ -598,7 +603,8 @@ static void shmem_truncate_range(struct
}
if (offset)
offset = 0;
- else if (subdir && !page_private(subdir)) {
+ else if (subdir &&
+ (!punch_hole || limit - idx >= ENTRIES_PER_PAGE)) {
dir[diroff] = NULL;
nr_pages_to_free++;
list_add(&subdir->lru, &pages_to_free);
_
Patches currently in -mm which might be from mszeredi@xxxxxxx are
shmem-fix-bug-in-shmem_writepage.patch
shmem-dont-release-lock-for-hole-punching.patch
fix-quadratic-behavior-of-shrink_dcache_parent.patch
mm-shrink-parent-dentries-when-shrinking-slab.patch
add-filesystem-subtype-support.patch
consolidate-generic_writepages-and-mpage_writepages.patch
-
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