On Wed, Nov 28, 2012 at 05:48:24PM +0100, Michal Hocko wrote: > On Wed 28-11-12 17:46:40, Michal Hocko wrote: > > On Wed 28-11-12 11:37:36, Johannes Weiner wrote: > > > On Wed, Nov 28, 2012 at 05:04:47PM +0100, Michal Hocko wrote: > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > > > index 095d2b4..5abe441 100644 > > > > --- a/include/linux/memcontrol.h > > > > +++ b/include/linux/memcontrol.h > > > > @@ -57,13 +57,14 @@ extern int mem_cgroup_newpage_charge(struct page *page, struct mm_struct *mm, > > > > gfp_t gfp_mask); > > > > /* for swap handling */ > > > > extern int mem_cgroup_try_charge_swapin(struct mm_struct *mm, > > > > - struct page *page, gfp_t mask, struct mem_cgroup **memcgp); > > > > + struct page *page, gfp_t mask, struct mem_cgroup **memcgp, > > > > + bool oom); > > > > > > Ok, now I feel almost bad for asking, but why the public interface, > > > too? > > > > Would it work out if I tell it was to double check that your review > > quality is not decreased after that many revisions? :P Deal. > >From e21bb704947e9a477ec1df9121575c606dbfcb52 Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@xxxxxxx> > Date: Wed, 28 Nov 2012 17:46:32 +0100 > Subject: [PATCH] memcg: do not trigger OOM from add_to_page_cache_locked > > memcg oom killer might deadlock if the process which falls down to > mem_cgroup_handle_oom holds a lock which prevents other task to > terminate because it is blocked on the very same lock. > This can happen when a write system call needs to allocate a page but > the allocation hits the memcg hard limit and there is nothing to reclaim > (e.g. there is no swap or swap limit is hit as well and all cache pages > have been reclaimed already) and the process selected by memcg OOM > killer is blocked on i_mutex on the same inode (e.g. truncate it). > > Process A > [<ffffffff811109b8>] do_truncate+0x58/0xa0 # takes i_mutex > [<ffffffff81121c90>] do_last+0x250/0xa30 > [<ffffffff81122547>] path_openat+0xd7/0x440 > [<ffffffff811229c9>] do_filp_open+0x49/0xa0 > [<ffffffff8110f7d6>] do_sys_open+0x106/0x240 > [<ffffffff8110f950>] sys_open+0x20/0x30 > [<ffffffff815b5926>] system_call_fastpath+0x18/0x1d > [<ffffffffffffffff>] 0xffffffffffffffff > > Process B > [<ffffffff8110a9c1>] mem_cgroup_handle_oom+0x241/0x3b0 > [<ffffffff8110b5ab>] T.1146+0x5ab/0x5c0 > [<ffffffff8110c22e>] mem_cgroup_cache_charge+0xbe/0xe0 > [<ffffffff810ca28c>] add_to_page_cache_locked+0x4c/0x140 > [<ffffffff810ca3a2>] add_to_page_cache_lru+0x22/0x50 > [<ffffffff810ca45b>] grab_cache_page_write_begin+0x8b/0xe0 > [<ffffffff81193a18>] ext3_write_begin+0x88/0x270 > [<ffffffff810c8fc6>] generic_file_buffered_write+0x116/0x290 > [<ffffffff810cb3cc>] __generic_file_aio_write+0x27c/0x480 > [<ffffffff810cb646>] generic_file_aio_write+0x76/0xf0 # takes ->i_mutex > [<ffffffff8111156a>] do_sync_write+0xea/0x130 > [<ffffffff81112183>] vfs_write+0xf3/0x1f0 > [<ffffffff81112381>] sys_write+0x51/0x90 > [<ffffffff815b5926>] system_call_fastpath+0x18/0x1d > [<ffffffffffffffff>] 0xffffffffffffffff > > This is not a hard deadlock though because administrator can still > intervene and increase the limit on the group which helps the writer to > finish the allocation and release the lock. > > This patch heals the problem by forbidding OOM from page cache charges > (namely add_ro_page_cache_locked). mem_cgroup_cache_charge grows oom > argument which is pushed down the call chain. > > As a possibly visible result add_to_page_cache_lru might fail more often > with ENOMEM but this is to be expected if the limit is set and it is > preferable than OOM killer IMO. > > Changes since v1 > - do not abuse gfp_flags and rather use oom parameter directly as per > Johannes > - handle also shmem write fauls resp. fallocate properly as per Johannes > > Reported-by: azurIt <azurit@xxxxxxxx> > Signed-off-by: Michal Hocko <mhocko@xxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Thanks, Michal! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>