On Fri, Oct 25, 2019 at 5:35 PM Pavel Shilovsky <piastryyy@xxxxxxxxx> wrote:
>
> пт, 25 окт. 2019 г. в 13:52, Frank Sorenson <sorenson@xxxxxxxxxx>:
> >
> > fI'm testing out multiple processes simultaneously doing an
> > open/read/write/close of the same file + smb restart test (next step
> > after the open/read/close + smb restart), and I'm hitting a different hang.
> >
> > It's a bit more complex, so I haven't been able to unravel it like the
> > other hangs.
> >
> > I'm using upstream 531e93d11470 with additional patches to fix the
> > recent crashes and deadlocks that the multiple-process open/read/close +
> > smb restart test hits:
> >
> > Author: Pavel Shilovsky <piastryyy@xxxxxxxxx>
> > Date: 2019-10-23 15:55:40 -0700
> >
> > CIFS: Fix use after free of file info structures
> >
> > Author: Pavel Shilovsky <piastryyy@xxxxxxxxx>
> > Date: 2019-10-22 15:35:34 -0700
> >
> > CIFS: Fix retry mid list corruption on reconnects
> >
> > Author: Dave Wysochanski <dwysocha@xxxxxxxxxx>
> > Date: 2019-10-23 22:08:22 -0400
> >
> > cifs: Fix cifsInodeInfo lock_sem deadlock when reconnect occurs
> >
> >
> > (I've hit this hang both with and without the 'lock_sem deadlock' patch,
> > so at least the patch does not make things worse)
> >
> >
> > on the client, I'm running 50 processes:
> > fd = open(testfile_path, O_RDWR|O_CREAT, 0644)
> > read(fd, buf, 32768);
> > write(fd, testfile_path, strlen(testfile_path);
> > close(fd);
> >
> > on smb server (once):
> > systemctl restart smb.service
> >
> >
> >
> > there are 6 processes looping to while trying to down_write
> > cinode->lock_sem, 5 of them from _cifsFileInfo_put, and one from
> > cifs_new_fileinfo
> >
> > and there are 5 other processes which are blocked, several of them
> > waiting on either PG_writeback or PG_locked (which are both set), all
> > for the same page of the file
> >
> > 2 inode_lock() (inode->i_rwsem) for the file
> > 1 wait_on_page_writeback() for the page
> > 1 down_read(inode->i_rwsem) for the inode of the directory
> > 1 inode_lock()(inode->i_rwsem) for the inode of the directory
> > 1 __lock_page
> >
> >
> > so processes are blocked waiting on:
> > page flags PG_locked and PG_writeback for one specific page
> > inode->i_rwsem for the directory
> > inode->i_rwsem for the file
> > cifsInodeInfo->lock_sem
> >
> >
> >
> > here are the more gory details (let me know if I need to provide
> > anything more/better):
> >
> > [0 00:48:22.765] [UN] PID: 8863 TASK: ffff8c691547c5c0 CPU: 3
> > COMMAND: "reopen_file"
> > #0 [ffff9965007e3ba8] __schedule at ffffffff9b6e6095
> > #1 [ffff9965007e3c38] schedule at ffffffff9b6e64df
> > #2 [ffff9965007e3c48] rwsem_down_write_slowpath at ffffffff9af283d7
> > #3 [ffff9965007e3cb8] legitimize_path at ffffffff9b0f975d
> > #4 [ffff9965007e3d08] path_openat at ffffffff9b0fe55d
> > #5 [ffff9965007e3dd8] do_filp_open at ffffffff9b100a33
> > #6 [ffff9965007e3ee0] do_sys_open at ffffffff9b0eb2d6
> > #7 [ffff9965007e3f38] do_syscall_64 at ffffffff9ae04315
> > * (I think legitimize_path is bogus)
> >
> > in path_openat
> > } else {
> > const char *s = path_init(nd, flags);
> > while (!(error = link_path_walk(s, nd)) &&
> > (error = do_last(nd, file, op)) > 0) { <<<<
> >
> > do_last:
> > if (open_flag & O_CREAT)
> > inode_lock(dir->d_inode); <<<<
> > else
> > so it's trying to take inode->i_rwsem for the directory
> >
> > DENTRY INODE SUPERBLK TYPE PATH
> > ffff8c68bb8e79c0 ffff8c691158ef20 ffff8c6915bf9000 DIR /mnt/vm1_smb/
> > inode.i_rwsem is ffff8c691158efc0
> >
> > <struct rw_semaphore 0xffff8c691158efc0>:
> > owner: <struct task_struct 0xffff8c6914275d00> (UN - 8856 -
> > reopen_file), counter: 0x0000000000000003
> > waitlist: 2
> > 0xffff9965007e3c90 8863 reopen_file UN 0 1:29:22.926
> > RWSEM_WAITING_FOR_WRITE
> > 0xffff996500393e00 9802 ls UN 0 1:17:26.700
> > RWSEM_WAITING_FOR_READ
> >
> >
> > the owner of the inode.i_rwsem of the directory is:
> >
> > [0 00:00:00.109] [UN] PID: 8856 TASK: ffff8c6914275d00 CPU: 3
> > COMMAND: "reopen_file"
> > #0 [ffff99650065b828] __schedule at ffffffff9b6e6095
> > #1 [ffff99650065b8b8] schedule at ffffffff9b6e64df
> > #2 [ffff99650065b8c8] schedule_timeout at ffffffff9b6e9f89
> > #3 [ffff99650065b940] msleep at ffffffff9af573a9
> > #4 [ffff99650065b948] _cifsFileInfo_put.cold.63 at ffffffffc0a42dd6 [cifs]
> > #5 [ffff99650065ba38] cifs_writepage_locked at ffffffffc0a0b8f3 [cifs]
> > #6 [ffff99650065bab0] cifs_launder_page at ffffffffc0a0bb72 [cifs]
> > #7 [ffff99650065bb30] invalidate_inode_pages2_range at ffffffff9b04d4bd
> > #8 [ffff99650065bcb8] cifs_invalidate_mapping at ffffffffc0a11339 [cifs]
> > #9 [ffff99650065bcd0] cifs_revalidate_mapping at ffffffffc0a1139a [cifs]
> > #10 [ffff99650065bcf0] cifs_d_revalidate at ffffffffc0a014f6 [cifs]
> > #11 [ffff99650065bd08] path_openat at ffffffff9b0fe7f7
> > #12 [ffff99650065bdd8] do_filp_open at ffffffff9b100a33
> > #13 [ffff99650065bee0] do_sys_open at ffffffff9b0eb2d6
> > #14 [ffff99650065bf38] do_syscall_64 at ffffffff9ae04315
> >
> > cifs_launder_page is for page 0xffffd1e2c07d2480
> >
> > crash> page.index,mapping,flags 0xffffd1e2c07d2480
> > index = 0x8
> > mapping = 0xffff8c68f3cd0db0
> > flags = 0xfffffc0008095
> >
> > PAGE-FLAG BIT VALUE
> > PG_locked 0 0000001
> > PG_uptodate 2 0000004
> > PG_lru 4 0000010
> > PG_waiters 7 0000080
> > PG_writeback 15 0008000
> >
> >
> > inode is ffff8c68f3cd0c40
> > inode.i_rwsem is ffff8c68f3cd0ce0
> > DENTRY INODE SUPERBLK TYPE PATH
> > ffff8c68a1f1b480 ffff8c68f3cd0c40 ffff8c6915bf9000 REG
> > /mnt/vm1_smb/testfile.8853
> >
> >
> > this process holds the inode->i_rwsem for the parent directory, is
> > laundering a page attached to the inode of the file it's opening, and in
> > _cifsFileInfo_put is trying to down_write the cifsInodeInfo->lock_sem
> > for the file itself.
> >
> >
> > <struct rw_semaphore 0xffff8c68f3cd0ce0>:
> > owner: <struct task_struct 0xffff8c6914272e80> (UN - 8854 -
> > reopen_file), counter: 0x0000000000000003
> > waitlist: 1
> > 0xffff9965005dfd80 8855 reopen_file UN 0 1:29:22.912
> > RWSEM_WAITING_FOR_WRITE
> >
> > this is the inode.i_rwsem for the file
> >
> > the owner:
> >
> > [0 00:48:22.739] [UN] PID: 8854 TASK: ffff8c6914272e80 CPU: 2
> > COMMAND: "reopen_file"
> > #0 [ffff99650054fb38] __schedule at ffffffff9b6e6095
> > #1 [ffff99650054fbc8] schedule at ffffffff9b6e64df
> > #2 [ffff99650054fbd8] io_schedule at ffffffff9b6e68e2
> > #3 [ffff99650054fbe8] __lock_page at ffffffff9b03c56f
> > #4 [ffff99650054fc80] pagecache_get_page at ffffffff9b03dcdf
> > #5 [ffff99650054fcc0] grab_cache_page_write_begin at ffffffff9b03ef4c
> > #6 [ffff99650054fcd0] cifs_write_begin at ffffffffc0a064ec [cifs]
> > #7 [ffff99650054fd30] generic_perform_write at ffffffff9b03bba4
> > #8 [ffff99650054fda8] __generic_file_write_iter at ffffffff9b04060a
> > #9 [ffff99650054fdf0] cifs_strict_writev.cold.70 at ffffffffc0a4469b [cifs]
> > #10 [ffff99650054fe48] new_sync_write at ffffffff9b0ec1dd
> > #11 [ffff99650054fed0] vfs_write at ffffffff9b0eed35
> > #12 [ffff99650054ff00] ksys_write at ffffffff9b0eefd9
> > #13 [ffff99650054ff38] do_syscall_64 at ffffffff9ae04315
> >
> > the process holds the inode->i_rwsem for the file to which it's writing,
> > and is trying to __lock_page for the same page as in the other processes
> >
> >
> > the other tasks:
> > [0 00:00:00.028] [UN] PID: 8859 TASK: ffff8c6915479740 CPU: 2
> > COMMAND: "reopen_file"
> > #0 [ffff9965007b39d8] __schedule at ffffffff9b6e6095
> > #1 [ffff9965007b3a68] schedule at ffffffff9b6e64df
> > #2 [ffff9965007b3a78] schedule_timeout at ffffffff9b6e9f89
> > #3 [ffff9965007b3af0] msleep at ffffffff9af573a9
> > #4 [ffff9965007b3af8] cifs_new_fileinfo.cold.61 at ffffffffc0a42a07 [cifs]
> > #5 [ffff9965007b3b78] cifs_open at ffffffffc0a0709d [cifs]
> > #6 [ffff9965007b3cd8] do_dentry_open at ffffffff9b0e9b7a
> > #7 [ffff9965007b3d08] path_openat at ffffffff9b0fe34f
> > #8 [ffff9965007b3dd8] do_filp_open at ffffffff9b100a33
> > #9 [ffff9965007b3ee0] do_sys_open at ffffffff9b0eb2d6
> > #10 [ffff9965007b3f38] do_syscall_64 at ffffffff9ae04315
> >
> > this is opening the file, and is trying to down_write cinode->lock_sem
> >
> >
> > [0 00:00:00.041] [UN] PID: 8860 TASK: ffff8c691547ae80 CPU: 2
> > COMMAND: "reopen_file"
> > [0 00:00:00.057] [UN] PID: 8861 TASK: ffff8c6915478000 CPU: 3
> > COMMAND: "reopen_file"
> > [0 00:00:00.059] [UN] PID: 8858 TASK: ffff8c6914271740 CPU: 2
> > COMMAND: "reopen_file"
> > [0 00:00:00.109] [UN] PID: 8862 TASK: ffff8c691547dd00 CPU: 6
> > COMMAND: "reopen_file"
> > #0 [ffff9965007c3c78] __schedule at ffffffff9b6e6095
> > #1 [ffff9965007c3d08] schedule at ffffffff9b6e64df
> > #2 [ffff9965007c3d18] schedule_timeout at ffffffff9b6e9f89
> > #3 [ffff9965007c3d90] msleep at ffffffff9af573a9
> > #4 [ffff9965007c3d98] _cifsFileInfo_put.cold.63 at ffffffffc0a42dd6 [cifs]
> > #5 [ffff9965007c3e88] cifs_close at ffffffffc0a07aaf [cifs]
> > #6 [ffff9965007c3ea0] __fput at ffffffff9b0efa6e
> > #7 [ffff9965007c3ee8] task_work_run at ffffffff9aef1614
> > #8 [ffff9965007c3f20] exit_to_usermode_loop at ffffffff9ae03d6f
> > #9 [ffff9965007c3f38] do_syscall_64 at ffffffff9ae0444c
> >
> > closing the file, and trying to down_write cifsi->lock_sem
> >
> >
> > [0 00:48:22.839] [UN] PID: 8857 TASK: ffff8c6914270000 CPU: 7
> > COMMAND: "reopen_file"
> > #0 [ffff9965006a7cc8] __schedule at ffffffff9b6e6095
> > #1 [ffff9965006a7d58] schedule at ffffffff9b6e64df
> > #2 [ffff9965006a7d68] io_schedule at ffffffff9b6e68e2
> > #3 [ffff9965006a7d78] wait_on_page_bit at ffffffff9b03cac6
> > #4 [ffff9965006a7e10] __filemap_fdatawait_range at ffffffff9b03b028
> > #5 [ffff9965006a7ed8] filemap_write_and_wait at ffffffff9b040165
> > #6 [ffff9965006a7ef0] cifs_flush at ffffffffc0a0c2fa [cifs]
> > #7 [ffff9965006a7f10] filp_close at ffffffff9b0e93f1
> > #8 [ffff9965006a7f30] __x64_sys_close at ffffffff9b0e9a0e
> > #9 [ffff9965006a7f38] do_syscall_64 at ffffffff9ae04315
> >
> > in __filemap_fdatawait_range
> > wait_on_page_writeback(page);
> > for the same page of the file
> >
> >
> >
> > [0 00:48:22.718] [UN] PID: 8855 TASK: ffff8c69142745c0 CPU: 7
> > COMMAND: "reopen_file"
> > #0 [ffff9965005dfc98] __schedule at ffffffff9b6e6095
> > #1 [ffff9965005dfd28] schedule at ffffffff9b6e64df
> > #2 [ffff9965005dfd38] rwsem_down_write_slowpath at ffffffff9af283d7
> > #3 [ffff9965005dfdf0] cifs_strict_writev at ffffffffc0a0c40a [cifs]
> > #4 [ffff9965005dfe48] new_sync_write at ffffffff9b0ec1dd
> > #5 [ffff9965005dfed0] vfs_write at ffffffff9b0eed35
> > #6 [ffff9965005dff00] ksys_write at ffffffff9b0eefd9
> > #7 [ffff9965005dff38] do_syscall_64 at ffffffff9ae04315
> >
> > inode_lock(inode);
> >
> >
> > and one 'ls' later on, to see whether the rest of the mount is available
> > (the test file is in the root, so we get blocked up on the directory
> > ->i_rwsem), so the entire mount is unavailable
> >
> > [0 00:36:26.473] [UN] PID: 9802 TASK: ffff8c691436ae80 CPU: 4
> > COMMAND: "ls"
> > #0 [ffff996500393d28] __schedule at ffffffff9b6e6095
> > #1 [ffff996500393db8] schedule at ffffffff9b6e64df
> > #2 [ffff996500393dc8] rwsem_down_read_slowpath at ffffffff9b6e9421
> > #3 [ffff996500393e78] down_read_killable at ffffffff9b6e95e2
> > #4 [ffff996500393e88] iterate_dir at ffffffff9b103c56
> > #5 [ffff996500393ec8] ksys_getdents64 at ffffffff9b104b0c
> > #6 [ffff996500393f30] __x64_sys_getdents64 at ffffffff9b104bb6
> > #7 [ffff996500393f38] do_syscall_64 at ffffffff9ae04315
> >
> > in iterate_dir:
> > if (shared)
> > res = down_read_killable(&inode->i_rwsem); <<<<
> > else
> > res = down_write_killable(&inode->i_rwsem);
> >
> >
> >
> > mount looks like:
> > 271 97 0:51 / /mnt/vm1_smb rw,relatime shared:143 - cifs //vm1/cifs
> > rw,vers=2.1,sec=ntlmssp,cache=strict,username=user1,uid=0,noforceuid,gid=0,noforcegid,addr=192.168.122.73,file_mode=0755,dir_mode=0755,hard,nounix,serverino,mapposix,rsize=1048576,wsize=1048576,bsize=1048576,echo_interval=60,actimeo=1
> >
> >
> >
> > # cat /proc/fs/cifs/DebugData
> > Display Internal CIFS Data Structures for Debugging
> > ---------------------------------------------------
> > CIFS Version 2.23
> > Features:
> > DFS,STATS2,DEBUG,ALLOW_INSECURE_LEGACY,WEAK_PW_HASH,CIFS_POSIX,UPCALL(SPNEGO),XATTR,ACL
> > CIFSMaxBufSize: 16384
> > Active VFS Requests: 2
> > Servers:
> > Number of credits: 241 Dialect 0x210
> > 1) Name: 192.168.122.73 Uses: 1 Capability: 0x300007 Session Status: 1
> > TCP status: 1 Instance: 3
> > Local Users To Server: 1 SecMode: 0x1 Req On Wire: 0 In Send: 0 In
> > MaxReq Wait: 0 SessionId: 0xd90a3306
> > Shares:
> > 0) IPC: \\vm1\IPC$ Mounts: 1 DevInfo: 0x0 Attributes: 0x0
> > PathComponentMax: 0 Status: 1 type: 0 Serial Number: 0x0
> >
> > 1) \\vm1\cifs Mounts: 1 DevInfo: 0x20 Attributes: 0x1006f
> > PathComponentMax: 255 Status: 1 type: DISK Serial Number: 0x0
> >
> > MIDs:
> >
> >
> > Frank
> > --
> > Frank Sorenson
> > sorenson@xxxxxxxxxx
> > Principal Software Maintenance Engineer
> > Global Support Services - filesystems
> > Red Hat
>
> Hi Frank,
>
> Thanks for the detailed analysis. So, there is a deadlock between a
> page lock and a cinode->lock_sem.
>
> It seems that the easiest fix would be to change all the places where
> we use get/put reference to a file info to offload the last step (to
> put a file info back) into a work queue, so, it can be lazily closed
> from a separate process that doesn't hold other locks.
>
>
I have also reproduced this while testing the latest patches.
I agree with what you're suggesting - sounds like a good approach.
Thanks.
