On Mon, 25 Apr 2011, Willy Tarreau wrote: > 2.6.27.59-stable review patch. If anyone has any objections, please let us > know. > > ------------------ > > From: Bob Liu <[email protected]> > > commit b836aec53e2bce71de1d5415313380688c851477 upstream. > > On no-mmu arch, there is a memleak during shmem test. The cause of this > memleak is ramfs_nommu_expand_for_mapping() added page refcount to 2 > which makes iput() can't free that pages. > ... > > Signed-off-by: Bob Liu <[email protected]> > Acked-by: Hugh Dickins <[email protected]> > Signed-off-by: David Howells <[email protected]> > Signed-off-by: Andrew Morton <[email protected]> > Signed-off-by: Linus Torvalds <[email protected]> > Signed-off-by: Greg Kroah-Hartman <[email protected]> > > --- > fs/ramfs/file-nommu.c | 1 + > 1 file changed, 1 insertion(+) > > --- a/fs/ramfs/file-nommu.c > +++ b/fs/ramfs/file-nommu.c > @@ -111,6 +111,7 @@ int ramfs_nommu_expand_for_mapping(struc > SetPageDirty(page); > > unlock_page(page); > + put_page(page); > } > > return 0;
I'm not absolutely certain, but I rather think this patch should NOT be included: I never looked to see when the bug it fixes crept in, but now I'm thinking it may have been 2678958e1225 "ramfs-nommu: use generic lru cache", which did not go in until 2.6.30 - __lru_cache_add adding the unbalanced page_cache_get. Whereas the "SetPageDirty" you can see above is not in 2.6.27.59-rc1: I think you'd do well to include the patch below which introduced it. (It may give you a reject because __pagevec_lru_add was enhanced to __pagevec_lru_add_file by the time that patch went in.) Yes, the pages Enrik reports as being wrongly discarded, would not have been discarded if their reference counts were too high: I do believe you need Enrik's patch instead of Bob's patch. Hugh commit 020fe22ff14320927f394de222cbb11708bcc7a8 Author: Enrik Berkhan <[email protected]> Date: Fri Mar 13 13:51:56 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 <[email protected]> Signed-off-by: David Howells <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Nick Piggin <[email protected]> Cc: Johannes Weiner <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> 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); } _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
