user/sven/linux.git, branch v3.14.51

Linux 3.14.51

2015-08-17T03:53:12Z

mm, vmscan: Do not wait for page writeback for GFP_NOFS allocations

2015-08-17T03:51:55Z

commit ecf5fc6e9654cd7a268c782a523f072b2f1959f9 upstream. Nikolay has reported a hang when a memcg reclaim got stuck with the following backtrace: PID: 18308 TASK: ffff883d7c9b0a30 CPU: 1 COMMAND: "rsync" #0 __schedule at ffffffff815ab152 #1 schedule at ffffffff815ab76e #2 schedule_timeout at ffffffff815ae5e5 #3 io_schedule_timeout at ffffffff815aad6a #4 bit_wait_io at ffffffff815abfc6 #5 __wait_on_bit at ffffffff815abda5 #6 wait_on_page_bit at ffffffff8111fd4f #7 shrink_page_list at ffffffff81135445 #8 shrink_inactive_list at ffffffff81135845 #9 shrink_lruvec at ffffffff81135ead #10 shrink_zone at ffffffff811360c3 #11 shrink_zones at ffffffff81136eff #12 do_try_to_free_pages at ffffffff8113712f #13 try_to_free_mem_cgroup_pages at ffffffff811372be #14 try_charge at ffffffff81189423 #15 mem_cgroup_try_charge at ffffffff8118c6f5 #16 __add_to_page_cache_locked at ffffffff8112137d #17 add_to_page_cache_lru at ffffffff81121618 #18 pagecache_get_page at ffffffff8112170b #19 grow_dev_page at ffffffff811c8297 #20 __getblk_slow at ffffffff811c91d6 #21 __getblk_gfp at ffffffff811c92c1 #22 ext4_ext_grow_indepth at ffffffff8124565c #23 ext4_ext_create_new_leaf at ffffffff81246ca8 #24 ext4_ext_insert_extent at ffffffff81246f09 #25 ext4_ext_map_blocks at ffffffff8124a848 #26 ext4_map_blocks at ffffffff8121a5b7 #27 mpage_map_one_extent at ffffffff8121b1fa #28 mpage_map_and_submit_extent at ffffffff8121f07b #29 ext4_writepages at ffffffff8121f6d5 #30 do_writepages at ffffffff8112c490 #31 __filemap_fdatawrite_range at ffffffff81120199 #32 filemap_flush at ffffffff8112041c #33 ext4_alloc_da_blocks at ffffffff81219da1 #34 ext4_rename at ffffffff81229b91 #35 ext4_rename2 at ffffffff81229e32 #36 vfs_rename at ffffffff811a08a5 #37 SYSC_renameat2 at ffffffff811a3ffc #38 sys_renameat2 at ffffffff811a408e #39 sys_rename at ffffffff8119e51e #40 system_call_fastpath at ffffffff815afa89 Dave Chinner has properly pointed out that this is a deadlock in the reclaim code because ext4 doesn't submit pages which are marked by PG_writeback right away. The heuristic was introduced by commit e62e384e9da8 ("memcg: prevent OOM with too many dirty pages") and it was applied only when may_enter_fs was specified. The code has been changed by c3b94f44fcb0 ("memcg: further prevent OOM with too many dirty pages") which has removed the __GFP_FS restriction with a reasoning that we do not get into the fs code. But this is not sufficient apparently because the fs doesn't necessarily submit pages marked PG_writeback for IO right away. ext4_bio_write_page calls io_submit_add_bh but that doesn't necessarily submit the bio. Instead it tries to map more pages into the bio and mpage_map_one_extent might trigger memcg charge which might end up waiting on a page which is marked PG_writeback but hasn't been submitted yet so we would end up waiting for something that never finishes. Fix this issue by replacing __GFP_IO by may_enter_fs check (for case 2) before we go to wait on the writeback. The page fault path, which is the only path that triggers memcg oom killer since 3.12, shouldn't require GFP_NOFS and so we shouldn't reintroduce the premature OOM killer issue which was originally addressed by the heuristic. As per David Chinner the xfs is doing similar thing since 2.6.15 already so ext4 is not the only affected filesystem. Moreover he notes: : For example: IO completion might require unwritten extent conversion : which executes filesystem transactions and GFP_NOFS allocations. The : writeback flag on the pages can not be cleared until unwritten : extent conversion completes. Hence memory reclaim cannot wait on : page writeback to complete in GFP_NOFS context because it is not : safe to do so, memcg reclaim or otherwise. [tytso@mit.edu: corrected the control flow] Fixes: c3b94f44fcb0 ("memcg: further prevent OOM with too many dirty pages") Reported-by: Nikolay Borisov Signed-off-by: Michal Hocko Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

md/bitmap: return an error when bitmap superblock is corrupt.

2015-08-17T03:51:54Z

commit b97e92574c0bf335db1cd2ec491d8ff5cd5d0b49 upstream Use separate bitmaps for each nodes in the cluster bitmap_read_sb() validates the bitmap superblock that it reads in. If it finds an inconsistency like a bad magic number or out-of-range version number, it prints an error and returns, but it incorrectly returns zero, so the array is still assembled with the (invalid) bitmap. This means it could try to use a bitmap with a new version number which it therefore does not understand. This bug was introduced in 3.5 and fix as part of a larger patch in 4.1. So the patch is suitable for any -stable kernel in that range. Fixes: 27581e5ae01f ("md/bitmap: centralise allocation of bitmap file pages.") Signed-off-by: NeilBrown Reported-by: GuoQing Jiang

path_openat(): fix double fput()

2015-08-17T03:51:54Z

commit f15133df088ecadd141ea1907f2c96df67c729f0 upstream. path_openat() jumps to the wrong place after do_tmpfile() - it has already done path_cleanup() (as part of path_lookupat() called by do_tmpfile()), so doing that again can lead to double fput(). Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

kvm: x86: fix kvm_apic_has_events to check for NULL pointer

2015-08-17T03:51:54Z

commit ce40cd3fc7fa40a6119e5fe6c0f2bc0eb4541009 upstream. Malicious (or egregiously buggy) userspace can trigger it, but it should never happen in normal operation. Signed-off-by: Paolo Bonzini Signed-off-by: Wang Kai Signed-off-by: Greg Kroah-Hartman

dcache: don't need rcu in shrink_dentry_list()

2015-08-17T03:51:54Z

commit 60942f2f235ce7b817166cdf355eed729094834d upstream. Since now the shrink list is private and nobody can free the dentry while it is on the shrink list, we can remove RCU protection from this. Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro Cc: "Nicholas A. Bellinger" Signed-off-by: Greg Kroah-Hartman

more graceful recovery in umount_collect()

2015-08-17T03:51:53Z

commit 9c8c10e262e0f62cb2530f1b076de979123183dd upstream. Start with shrink_dcache_parent(), then scan what remains. First of all, BUG() is very much an overkill here; we are holding ->s_umount, and hitting BUG() means that a lot of interesting stuff will be hanging after that point (sync(2), for example). Moreover, in cases when there had been more than one leak, we'll be better off reporting all of them. And more than just the last component of pathname - %pd is there for just such uses... That was the last user of dentry_lru_del(), so kill it off... Signed-off-by: Al Viro Cc: "Nicholas A. Bellinger" Signed-off-by: Greg Kroah-Hartman

don't remove from shrink list in select_collect()

2015-08-17T03:51:53Z

commit fe91522a7ba82ca1a51b07e19954b3825e4aaa22 upstream. If we find something already on a shrink list, just increment data->found and do nothing else. Loops in shrink_dcache_parent() and check_submounts_and_drop() will do the right thing - everything we did put into our list will be evicted and if there had been nothing, but data->found got non-zero, well, we have somebody else shrinking those guys; just try again. Signed-off-by: Al Viro Cc: "Nicholas A. Bellinger" Signed-off-by: Greg Kroah-Hartman

dentry_kill(): don't try to remove from shrink list

2015-08-17T03:51:53Z

commit 41edf278fc2f042f4e22a12ed87d19c5201210e1 upstream. If the victim in on the shrink list, don't remove it from there. If shrink_dentry_list() manages to remove it from the list before we are done - fine, we'll just free it as usual. If not - mark it with new flag (DCACHE_MAY_FREE) and leave it there. Eventually, shrink_dentry_list() will get to it, remove the sucker from shrink list and call dentry_kill(dentry, 0). Which is where we'll deal with freeing. Since now dentry_kill(dentry, 0) may happen after or during dentry_kill(dentry, 1), we need to recognize that (by seeing DCACHE_DENTRY_KILLED already set), unlock everything and either free the sucker (in case DCACHE_MAY_FREE has been set) or leave it for ongoing dentry_kill(dentry, 1) to deal with. Signed-off-by: Al Viro Cc: "Nicholas A. Bellinger" Signed-off-by: Greg Kroah-Hartman

expand the call of dentry_lru_del() in dentry_kill()

2015-08-17T03:51:53Z

commit 01b6035190b024240a43ac1d8e9c6f964f5f1c63 upstream. Signed-off-by: Al Viro Cc: "Nicholas A. Bellinger" Signed-off-by: Greg Kroah-Hartman