Re: [PATCH v4] ntfs: serialize attribute-list replacement with lookups

[Hyunchul Lee]

Hi Cen,

While running generic/013 from xfstests, I observed the following hung
task warning:

[  492.533956] INFO: task fsstress:934 blocked for more than 122 seconds.
[  492.534445]       Tainted: G           O        7.1.0-g81fe702ff176 #2
[  492.534870] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[  492.535914] INFO: task fsstress:934 <reader> blocked on an
rw-semaphore likely owned by task fsstress:934 <writer>
[  492.536788] INFO: lockdep is turned off.

# ps -eo pid,comm,stat | grep " D"
    460 kworker/u16:4+f D
    934 fsstress        D+

# cat /proc/934/stack
[<0>] ntfs_attr_list_lock+0x2a/0x60 [ntfs]
[<0>] ntfs_attr_get_search_ctx+0x97/0x100 [ntfs]
[<0>] ntfs_resident_attr_resize+0x64/0x610 [ntfs]
[<0>] ntfs_ir_truncate+0x82/0x120 [ntfs]
[<0>] ntfs_ie_add+0x35/0x200 [ntfs]
[<0>] ntfs_index_add_filename+0xca/0x120 [ntfs]
[<0>] __ntfs_create+0xa9a/0xd80 [ntfs]
[<0>] ntfs_create+0xbd/0x170 [ntfs]
[<0>] path_openat+0x1014/0x1400
[<0>] do_file_open+0xdf/0x1a0
[<0>] do_sys_openat2+0x7b/0xe0
[<0>] __x64_sys_creat+0x45/0x70
[<0>] do_syscall_64+0x101/0x6a0
[<0>] entry_SYSCALL_64_after_hwframe+0x77/0x7f

# cat /proc/460/stack
[<0>] __ntfs_write_inode+0x7b/0x6b0 [ntfs]
[<0>] __writeback_single_inode+0x3f1/0x580
[<0>] writeback_sb_inodes+0x25b/0x8c0
[<0>] __writeback_inodes_wb+0x47/0xf0
[<0>] wb_writeback+0x216/0x440
[<0>] wb_workfn+0x3e6/0x510
[<0>] process_one_work+0x200/0x5e0
[<0>] worker_thread+0x1a0/0x370
[<0>] kthread+0xef/0x120
[<0>] ret_from_fork+0x270/0x330
[<0>] ret_from_fork_asm+0x1a/0x30