kernel.git/fs/nilfs2/page.c, branch linux-3.2.y

nilfs2: fix issue with race condition of competition between segments for dirty blocks

2013-10-26T20:06:07Z

commit 7f42ec3941560f0902fe3671e36f2c20ffd3af0a upstream. Many NILFS2 users were reported about strange file system corruption (for example): NILFS: bad btree node (blocknr=185027): level = 0, flags = 0x0, nchildren = 768 NILFS error (device sda4): nilfs_bmap_last_key: broken bmap (inode number=11540) But such error messages are consequence of file system's issue that takes place more earlier. Fortunately, Jerome Poulin and Anton Eliasson were reported about another issue not so recently. These reports describe the issue with segctor thread's crash: BUG: unable to handle kernel paging request at 0000000000004c83 IP: nilfs_end_page_io+0x12/0xd0 [nilfs2] Call Trace: nilfs_segctor_do_construct+0xf25/0x1b20 [nilfs2] nilfs_segctor_construct+0x17b/0x290 [nilfs2] nilfs_segctor_thread+0x122/0x3b0 [nilfs2] kthread+0xc0/0xd0 ret_from_fork+0x7c/0xb0 These two issues have one reason. This reason can raise third issue too. Third issue results in hanging of segctor thread with eating of 100% CPU. REPRODUCING PATH: One of the possible way or the issue reproducing was described by Jermoe me Poulin : 1. init S to get to single user mode. 2. sysrq+E to make sure only my shell is running 3. start network-manager to get my wifi connection up 4. login as root and launch "screen" 5. cd /boot/log/nilfs which is a ext3 mount point and can log when NILFS dies. 6. lscp | xz -9e > lscp.txt.xz 7. mount my snapshot using mount -o cp=3360839,ro /dev/vgUbuntu/root /mnt/nilfs 8. start a screen to dump /proc/kmsg to text file since rsyslog is killed 9. start a screen and launch strace -f -o find-cat.log -t find /mnt/nilfs -type f -exec cat {} > /dev/null \; 10. start a screen and launch strace -f -o apt-get.log -t apt-get update 11. launch the last command again as it did not crash the first time 12. apt-get crashes 13. ps aux > ps-aux-crashed.log 13. sysrq+W 14. sysrq+E wait for everything to terminate 15. sysrq+SUSB Simplified way of the issue reproducing is starting kernel compilation task and "apt-get update" in parallel. REPRODUCIBILITY: The issue is reproduced not stable [60% - 80%]. It is very important to have proper environment for the issue reproducing. The critical conditions for successful reproducing: (1) It should have big modified file by mmap() way. (2) This file should have the count of dirty blocks are greater that several segments in size (for example, two or three) from time to time during processing. (3) It should be intensive background activity of files modification in another thread. INVESTIGATION: First of all, it is possible to see that the reason of crash is not valid page address: NILFS [nilfs_segctor_complete_write]:2100 bh->b_count 0, bh->b_blocknr 13895680, bh->b_size 13897727, bh->b_page 0000000000001a82 NILFS [nilfs_segctor_complete_write]:2101 segbuf->sb_segnum 6783 Moreover, value of b_page (0x1a82) is 6786. This value looks like segment number. And b_blocknr with b_size values look like block numbers. So, buffer_head's pointer points on not proper address value. Detailed investigation of the issue is discovered such picture: [-----------------------------SEGMENT 6783-------------------------------] NILFS [nilfs_segctor_do_construct]:2310 nilfs_segctor_begin_construction NILFS [nilfs_segctor_do_construct]:2321 nilfs_segctor_collect NILFS [nilfs_segctor_do_construct]:2336 nilfs_segctor_assign NILFS [nilfs_segctor_do_construct]:2367 nilfs_segctor_update_segusage NILFS [nilfs_segctor_do_construct]:2371 nilfs_segctor_prepare_write NILFS [nilfs_segctor_do_construct]:2376 nilfs_add_checksums_on_logs NILFS [nilfs_segctor_do_construct]:2381 nilfs_segctor_write NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111149024, segbuf->sb_segnum 6783 [-----------------------------SEGMENT 6784-------------------------------] NILFS [nilfs_segctor_do_construct]:2310 nilfs_segctor_begin_construction NILFS [nilfs_segctor_do_construct]:2321 nilfs_segctor_collect NILFS [nilfs_lookup_dirty_data_buffers]:782 bh->b_count 1, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824 NILFS [nilfs_lookup_dirty_data_buffers]:783 bh->b_assoc_buffers.next ffff8802174a6798, bh->b_assoc_buffers.prev ffff880221cffee8 NILFS [nilfs_segctor_do_construct]:2336 nilfs_segctor_assign NILFS [nilfs_segctor_do_construct]:2367 nilfs_segctor_update_segusage NILFS [nilfs_segctor_do_construct]:2371 nilfs_segctor_prepare_write NILFS [nilfs_segctor_do_construct]:2376 nilfs_add_checksums_on_logs NILFS [nilfs_segctor_do_construct]:2381 nilfs_segctor_write NILFS [nilfs_segbuf_submit_bh]:575 bh->b_count 1, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824 NILFS [nilfs_segbuf_submit_bh]:576 segbuf->sb_segnum 6784 NILFS [nilfs_segbuf_submit_bh]:577 bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880218bcdf50 NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111150080, segbuf->sb_segnum 6784, segbuf->sb_nbio 0 [----------] ditto NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111164416, segbuf->sb_segnum 6784, segbuf->sb_nbio 15 [-----------------------------SEGMENT 6785-------------------------------] NILFS [nilfs_segctor_do_construct]:2310 nilfs_segctor_begin_construction NILFS [nilfs_segctor_do_construct]:2321 nilfs_segctor_collect NILFS [nilfs_lookup_dirty_data_buffers]:782 bh->b_count 2, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824 NILFS [nilfs_lookup_dirty_data_buffers]:783 bh->b_assoc_buffers.next ffff880219277e80, bh->b_assoc_buffers.prev ffff880221cffc88 NILFS [nilfs_segctor_do_construct]:2367 nilfs_segctor_update_segusage NILFS [nilfs_segctor_do_construct]:2371 nilfs_segctor_prepare_write NILFS [nilfs_segctor_do_construct]:2376 nilfs_add_checksums_on_logs NILFS [nilfs_segctor_do_construct]:2381 nilfs_segctor_write NILFS [nilfs_segbuf_submit_bh]:575 bh->b_count 2, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824 NILFS [nilfs_segbuf_submit_bh]:576 segbuf->sb_segnum 6785 NILFS [nilfs_segbuf_submit_bh]:577 bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880222cc7ee8 NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111165440, segbuf->sb_segnum 6785, segbuf->sb_nbio 0 [----------] ditto NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111177728, segbuf->sb_segnum 6785, segbuf->sb_nbio 12 NILFS [nilfs_segctor_do_construct]:2399 nilfs_segctor_wait NILFS [nilfs_segbuf_wait]:676 segbuf->sb_segnum 6783 NILFS [nilfs_segbuf_wait]:676 segbuf->sb_segnum 6784 NILFS [nilfs_segbuf_wait]:676 segbuf->sb_segnum 6785 NILFS [nilfs_segctor_complete_write]:2100 bh->b_count 0, bh->b_blocknr 13895680, bh->b_size 13897727, bh->b_page 0000000000001a82 BUG: unable to handle kernel paging request at 0000000000001a82 IP: [] nilfs_end_page_io+0x12/0xd0 [nilfs2] Usually, for every segment we collect dirty files in list. Then, dirty blocks are gathered for every dirty file, prepared for write and submitted by means of nilfs_segbuf_submit_bh() call. Finally, it takes place complete write phase after calling nilfs_end_bio_write() on the block layer. Buffers/pages are marked as not dirty on final phase and processed files removed from the list of dirty files. It is possible to see that we had three prepare_write and submit_bio phases before segbuf_wait and complete_write phase. Moreover, segments compete between each other for dirty blocks because on every iteration of segments processing dirty buffer_heads are added in several lists of payload_buffers: [SEGMENT 6784]: bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880218bcdf50 [SEGMENT 6785]: bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880222cc7ee8 The next pointer is the same but prev pointer has changed. It means that buffer_head has next pointer from one list but prev pointer from another. Such modification can be made several times. And, finally, it can be resulted in various issues: (1) segctor hanging, (2) segctor crashing, (3) file system metadata corruption. FIX: This patch adds: (1) setting of BH_Async_Write flag in nilfs_segctor_prepare_write() for every proccessed dirty block; (2) checking of BH_Async_Write flag in nilfs_lookup_dirty_data_buffers() and nilfs_lookup_dirty_node_buffers(); (3) clearing of BH_Async_Write flag in nilfs_segctor_complete_write(), nilfs_abort_logs(), nilfs_forget_buffer(), nilfs_clear_dirty_page(). Reported-by: Jerome Poulin Reported-by: Anton Eliasson Cc: Paul Fertser Cc: ARAI Shun-ichi Cc: Piotr Szymaniak Cc: Juan Barry Manuel Canham Cc: Zahid Chowdhury Cc: Elmer Zhang Cc: Kenneth Langga Signed-off-by: Vyacheslav Dubeyko Acked-by: Ryusuke Konishi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: nilfs_clear_dirty_page() has not been separated from nilfs_clear_dirty_pages()] Signed-off-by: Ben Hutchings

nilfs2: use mark_buffer_dirty to mark btnode or meta data dirty

2011-05-10T13:21:57Z

This replaces nilfs_mdt_mark_buffer_dirty and nilfs_btnode_mark_dirty macros with mark_buffer_dirty and gets rid of nilfs_mark_buffer_dirty, an own mark buffer dirty function. Signed-off-by: Ryusuke Konishi

nilfs2: always set back pointer to host inode in mapping->host

2011-05-10T13:21:57Z

In the current nilfs, page cache for btree nodes and meta data files do not set a valid back pointer to the host inode in mapping->host. This will change it so that every address space in nilfs uses mapping->host to hold its host inode. Signed-off-by: Ryusuke Konishi

nilfs2: get rid of private page allocator

2011-05-10T13:21:44Z

Previously, nilfs was cloning pages for mmapped region to freeze their data and ensure consistency of checksum during writeback cycles. A private page allocator was used for this page cloning. But, we no longer need to do that since clear_page_dirty_for_io function sets up pte so that vm_ops->page_mkwrite function is called right before the mmapped pages are modified and nilfs_page_mkwrite function can safely wait for the pages to be written back to disk. So, this stops making a copy of mmapped pages during writeback, and eliminates the private page allocation and deallocation functions from nilfs. Signed-off-by: Ryusuke Konishi

fs: export empty_aops

2011-04-05T21:51:48Z

With the ->sync_page() hook gone, we have a few users that add their own static address_space_operations without any functions defined. fs/inode.c already has an empty_aops that it uses for init purposes. Lets export that and use it in the places where an otherwise empty aops was defined. Signed-off-by: Jens Axboe

nilfs2: fix oops due to a bad aops initialization

2011-03-30T08:39:25Z

Nilfs in 2.6.39-rc1 hit the following oops: BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 IP: [] try_to_release_page+0x2a/0x3d PGD 234cb6067 PUD 234c72067 PMD 0 Oops: 0000 [#1] SMP Process truncate (pid: 10995, threadinfo ffff8802353c2000, task ffff880234cfa000) Stack: ffff8802333c77b8 ffffffff810b64b0 0000000000003802 ffffffffa0052cca 0000000000000000 ffff8802353c3b58 0000000000000000 ffff8802353c3b58 0000000000000001 0000000000000000 ffffea0007b92308 ffffea0007b92308 Call Trace: [] ? invalidate_inode_pages2_range+0x15f/0x273 [] ? nilfs_palloc_get_block+0x2d/0xaf [nilfs2] [] ? bit_waitqueue+0x14/0xa1 [] ? wake_up_bit+0x10/0x20 [] ? nilfs_forget_buffer+0x66/0x7a [nilfs2] [] ? nilfs_btree_concat_left+0x5c/0x77 [nilfs2] [] ? nilfs_btree_delete+0x395/0x3cf [nilfs2] [] ? nilfs_bmap_do_delete+0x6e/0x79 [nilfs2] [] ? nilfs_btree_last_key+0x14b/0x15e [nilfs2] [] ? nilfs_bmap_truncate+0x2f/0x83 [nilfs2] [] ? nilfs_bmap_last_key+0x35/0x62 [nilfs2] [] ? nilfs_truncate_bmap+0x6b/0xc7 [nilfs2] [] ? nilfs_truncate+0x79/0xe4 [nilfs2] [] ? vmtruncate+0x33/0x3b [] ? nilfs_setattr+0x4d/0x8c [nilfs2] [] ? do_page_fault+0x31b/0x356 [] ? notify_change+0x17d/0x262 [] ? do_truncate+0x65/0x80 [] ? sys_ftruncate+0xf1/0xf6 [] ? system_call_fastpath+0x16/0x1b Code: c3 48 83 ec 08 48 8b 17 48 8b 47 18 80 e2 01 75 04 0f 0b eb fe 48 8b 17 80 e6 20 74 05 31 c0 41 59 c3 48 85 c0 74 11 48 8b 40 58 8b 40 48 48 85 c0 74 04 41 58 ff e0 59 e9 b1 b5 05 00 41 54 RIP [] try_to_release_page+0x2a/0x3d RSP CR2: 0000000000000048 This oops was brought in by the change "block: remove per-queue plugging" (commit: 7eaceaccab5f40bb). It initializes mapping->a_ops with a NULL pointer for some pages in nilfs (e.g. btree node pages), but mm code doesn't NULL pointer checks against mapping->a_ops. (the check is done for each callback function) This corrects the aops initialization and fixes the oops. Signed-off-by: Ryusuke Konishi Acked-by: Jens Axboe

Merge branch 'for-2.6.39/stack-plug' into for-2.6.39/core

2011-03-10T07:58:35Z

Conflicts: block/blk-core.c block/blk-flush.c drivers/md/raid1.c drivers/md/raid10.c drivers/md/raid5.c fs/nilfs2/btnode.c fs/nilfs2/mdt.c Signed-off-by: Jens Axboe

block: remove per-queue plugging

2011-03-10T07:52:07Z

Code has been converted over to the new explicit on-stack plugging, and delay users have been converted to use the new API for that. So lets kill off the old plugging along with aops->sync_page(). Signed-off-by: Jens Axboe

mm: prevent concurrent unmap_mapping_range() on the same inode

2011-02-24T03:52:52Z

Michael Leun reported that running parallel opens on a fuse filesystem can trigger a "kernel BUG at mm/truncate.c:475" Gurudas Pai reported the same bug on NFS. The reason is, unmap_mapping_range() is not prepared for more than one concurrent invocation per inode. For example: thread1: going through a big range, stops in the middle of a vma and stores the restart address in vm_truncate_count. thread2: comes in with a small (e.g. single page) unmap request on the same vma, somewhere before restart_address, finds that the vma was already unmapped up to the restart address and happily returns without doing anything. Another scenario would be two big unmap requests, both having to restart the unmapping and each one setting vm_truncate_count to its own value. This could go on forever without any of them being able to finish. Truncate and hole punching already serialize with i_mutex. Other callers of unmap_mapping_range() do not, and it's difficult to get i_mutex protection for all callers. In particular ->d_revalidate(), which calls invalidate_inode_pages2_range() in fuse, may be called with or without i_mutex. This patch adds a new mutex to 'struct address_space' to prevent running multiple concurrent unmap_mapping_range() on the same mapping. [ We'll hopefully get rid of all this with the upcoming mm preemptibility series by Peter Zijlstra, the "mm: Remove i_mmap_mutex lockbreak" patch in particular. But that is for 2.6.39 ] Signed-off-by: Miklos Szeredi Reported-by: Michael Leun Reported-by: Gurudas Pai Tested-by: Gurudas Pai Acked-by: Hugh Dickins Cc: stable@kernel.org Signed-off-by: Linus Torvalds

nilfs2: fix a checkpatch error in page.c

2011-01-10T05:05:46Z

Will correct the following checkpatch error: ERROR: trailing whitespace #494: FILE: page.c:494: + $ Signed-off-by: Ryusuke Konishi