friendly ping... On 2021/1/5 21:46, Jan Kara wrote:
We found the following deadlock when running xfstests generic/390 with ext4 filesystem, and simutaneously offlining/onlining the disk we tested. It will cause a deadlock whose call trace is like this: fsstress D 0 11672 11625 0x00000080 Call Trace: ? __schedule+0x2fc/0x930 ? filename_parentat+0x10b/0x1a0 schedule+0x28/0x70 rwsem_down_read_failed+0x102/0x1c0 ? __percpu_down_read+0x93/0xb0 __percpu_down_read+0x93/0xb0 __sb_start_write+0x5f/0x70 mnt_want_write+0x20/0x50 do_renameat2+0x1f3/0x550 __x64_sys_rename+0x1c/0x20 do_syscall_64+0x5b/0x1b0 entry_SYSCALL_64_after_hwframe+0x65/0xca The root cause is that when ext4 hits IO error due to disk being offline, it will switch itself into read-only state. When it is frozen at that moment, following thaw_super() call will not unlock percpu freeze semaphores (as the fs is read-only) causing the deadlock. };
