Gitweb: http://git.kernel.org/linus/020fe22ff14320927f394de222cbb11708bcc7a8
Commit: 020fe22ff14320927f394de222cbb11708bcc7a8
Parent: 041b62374c7fedc11a8a1eeda2868612d3d1436c
Author: Enrik Berkhan <Enrik.Berkhan@ge.com>
AuthorDate: Fri Mar 13 13:51:56 2009 -0700
Committer: Linus Torvalds <torvalds@linux-foundation.org>
CommitDate: Sat Mar 14 11:57:22 2009 -0700
nommu: ramfs: pages allocated to an inode's pagecache may get wrongly discarded
The pages attached to a ramfs inode's pagecache by truncation from nothing
- as done by SYSV SHM for example - may get discarded under memory
pressure.
The problem is that the pages are not marked dirty. Anything that creates
data in an MMU-based ramfs will cause the pages holding that data will
cause the set_page_dirty() aop to be called.
For the NOMMU-based mmap, set_page_dirty() may be called by write(), but
it won't be called by page-writing faults on writable mmaps, and it isn't
called by ramfs_nommu_expand_for_mapping() when a file is being truncated
from nothing to allocate a contiguous run.
The solution is to mark the pages dirty at the point of allocation by the
truncation code.
Signed-off-by: Enrik Berkhan <Enrik.Berkhan@ge.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/ramfs/file-nommu.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
index b9b567a..90d72be 100644
--- a/fs/ramfs/file-nommu.c
+++ b/fs/ramfs/file-nommu.c
@@ -114,6 +114,9 @@ int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
if (!pagevec_add(&lru_pvec, page))
__pagevec_lru_add_file(&lru_pvec);
+ /* prevent the page from being discarded on memory pressure */
+ SetPageDirty(page);
+
unlock_page(page);
}
--
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