| Message ID | 20190923083030.6442-1-bhe@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | memcg: Only record foreign writebacks with dirty pages when memcg is not disabled | expand |
On 09/23/19 at 04:30pm, Baoquan He wrote: > --- > include/linux/memcontrol.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index ad8f1a397ae4..fa53f9d51205 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -1261,7 +1261,8 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct page *page, > static inline void mem_cgroup_track_foreign_dirty(struct page *page, > struct bdi_writeback *wb) > { > - if (unlikely(&page->mem_cgroup->css != wb->memcg_css)) > + if (unlikely(&page->mem_cgroup->css != wb->memcg_css) > + && !mem_cgroup_disabled()) Sorry, this is the draft patch I was testing. Later I think this had better be moved into mem_cgroup_track_foreign_dirty_slowpath(). Not very sure about this. Will send a v2 to match the patch log. > mem_cgroup_track_foreign_dirty_slowpath(page, wb); > } > > -- > 2.17.2 >
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index ad8f1a397ae4..fa53f9d51205 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1261,7 +1261,8 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct page *page, static inline void mem_cgroup_track_foreign_dirty(struct page *page, struct bdi_writeback *wb) { - if (unlikely(&page->mem_cgroup->css != wb->memcg_css)) + if (unlikely(&page->mem_cgroup->css != wb->memcg_css) + && !mem_cgroup_disabled()) mem_cgroup_track_foreign_dirty_slowpath(page, wb); }
In kdump kernel, memcg usually is disabled with 'cgroup_disable=memory' for saving memory. Now kdump kernel will always panic when dump vmcore to local disk: BUG: kernel NULL pointer dereference, address: 0000000000000ab8 PGD 5fcab067 P4D 5fcab067 PUD 5ff73067 PMD 0 Oops: 0000 [#1] SMP NOPTI CPU: 0 PID: 598 Comm: makedumpfile Not tainted 5.3.0+ #26 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 10/02/2018 RIP: 0010:mem_cgroup_track_foreign_dirty_slowpath+0x38/0x140 Code: 55 48 8b 2d 6a bd 12 01 53 4c 8b 67 38 0f 1f 44 00 00 49 8b 06 48 89 e9 31 db be ff ff ff ff 48 8b 38 49 8d 84 24 d0 0a 00 00 <48> 39 78 e8 74 5a 48 8b 50 f8 48 39 ca 79 0e 44 8b 00 41 83 f8 01 RSP: 0018:ffffbc9300817bd0 EFLAGS: 00010046 RAX: 0000000000000ad0 RBX: 0000000000000000 RCX: 00000000fffba227 RDX: fffffffffffffff8 RSI: 00000000ffffffff RDI: 0000000000000004 RBP: 00000000fffba227 R08: 0000000000030340 R09: ffffbc9300817d10 R10: 0000000000000000 R11: 0000000000001000 R12: 0000000000000000 R13: ffff999c1fa2bcf0 R14: ffff999c1f7bcc78 R15: ffffe51fc177a8c0 FS: 00007f84f14c2b80(0000) GS:ffff999c22200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000ab8 CR3: 000000005f564000 CR4: 00000000003406b0 Call Trace: __set_page_dirty+0x52/0xc0 iomap_set_page_dirty+0x50/0x90 iomap_write_end+0x6e/0x270 iomap_write_actor+0xce/0x170 ? iomap_write_end+0x270/0x270 iomap_apply+0xba/0x11e ? iomap_write_end+0x270/0x270 iomap_file_buffered_write+0x62/0x90 ? iomap_write_end+0x270/0x270 xfs_file_buffered_aio_write+0xca/0x320 [xfs] new_sync_write+0x12d/0x1d0 vfs_write+0xa5/0x1a0 ksys_write+0x59/0xd0 do_syscall_64+0x59/0x1e0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f84f1093ab5 And this will corrupt the 1st kernel too with 'cgroup_disable=memory'. From the trace and with debugging, it is pointing to commit 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") which introduced this regression. Disabling memcg causes the null pointer dereference at uninitialized data in function mem_cgroup_track_foreign_dirty_slowpath(). Fix it by returning directly if memcg is disabled, but not trying to record the foreign writebacks with dirty pages. Fixed: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Baoquan He <bhe@redhat.com> --- include/linux/memcontrol.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)