path: root/security/device_cgroup.c
diff options
authorJan Kara <jack@suse.cz>2012-10-25 13:37:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-25 14:37:52 -0700
commitef5d437f71afdf4afdbab99213add99f4b1318fd (patch)
treeda7a5b05ae7f3035e95d36824e975c06c103a22c /security/device_cgroup.c
parent4864ccbb5a6f99e4c44dc816304007547a268b9f (diff)
mm: fix XFS oops due to dirty pages without buffers on s390
On s390 any write to a page (even from kernel itself) sets architecture specific page dirty bit. Thus when a page is written to via buffered write, HW dirty bit gets set and when we later map and unmap the page, page_remove_rmap() finds the dirty bit and calls set_page_dirty(). Dirtying of a page which shouldn't be dirty can cause all sorts of problems to filesystems. The bug we observed in practice is that buffers from the page get freed, so when the page gets later marked as dirty and writeback writes it, XFS crashes due to an assertion BUG_ON(!PagePrivate(page)) in page_buffers() called from xfs_count_page_state(). Similar problem can also happen when zero_user_segment() call from xfs_vm_writepage() (or block_write_full_page() for that matter) set the hardware dirty bit during writeback, later buffers get freed, and then page unmapped. Fix the issue by ignoring s390 HW dirty bit for page cache pages of mappings with mapping_cap_account_dirty(). This is safe because for such mappings when a page gets marked as writeable in PTE it is also marked dirty in do_wp_page() or do_page_fault(). When the dirty bit is cleared by clear_page_dirty_for_io(), the page gets writeprotected in page_mkclean(). So pagecache page is writeable if and only if it is dirty. Thanks to Hugh Dickins for pointing out mapping has to have mapping_cap_account_dirty() for things to work and proposing a cleaned up variant of the patch. The patch has survived about two hours of running fsx-linux on tmpfs while heavily swapping and several days of running on out build machines where the original problem was triggered. Signed-off-by: Jan Kara <jack@suse.cz> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: <stable@vger.kernel.org> [3.0+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'security/device_cgroup.c')
0 files changed, 0 insertions, 0 deletions