From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: [4.3-rc1, regression] dax: hang on i_mmap_rwsem in generic/075 Date: Tue, 22 Sep 2015 13:05:55 +1000 Message-ID: <20150922030555.GA3902@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: willy@linux.intel.com, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org To: linux-fsdevel@vger.kernel.org Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Hi folks, I'm seeing hangs like this when using DAX on XFS on 4.3-rc1 running xfstests generic/075 (fsx test): # echo w > /proc/sysrq-trigger [71628.984872] sysrq: SysRq : Show Blocked State [71628.985988] task PC stack pid father [71628.987635] fsx D ffff88043fd756c0 12824 520 32636 0x00000000 [71628.989251] ffff88007f557ba8 0000000000000086 ffff88042eb40580 ffff8803c8bcc180 [71628.990645] ffff88007f558000 ffff88041d748e80 ffff88041d748e68 ffffffff00000000 [71628.992068] 00000000fffffffe ffff88007f557bc0 ffffffff81d855ca ffff8803c8bcc180 [71628.993639] Call Trace: [71628.994097] [] schedule+0x3a/0x90 [71628.994997] [] rwsem_down_write_failed+0x141/0x340 [71628.996197] [] call_rwsem_down_write_failed+0x13/0x20 [71628.997548] [] ? down_write+0x24/0x40 [71628.998502] [] __dax_fault+0x546/0x6c0 [71628.999469] [] ? xfs_get_blocks+0x20/0x20 [71629.000515] [] xfs_filemap_fault+0xc8/0xf0 [71629.001668] [] __do_fault+0x3d/0x80 [71629.002589] [] handle_mm_fault+0xb8a/0xfd0 [71629.003620] [] __do_page_fault+0x15f/0x420 [71629.004680] [] trace_do_page_fault+0x43/0x110 [71629.005877] [] do_async_page_fault+0x1a/0xa0 [71629.006936] [] async_page_fault+0x28/0x30 __dax_fault() gets stuck on this lock: (gdb) l *(__dax_fault+0x546) 0xffffffff812110b6 is in __dax_fault (include/linux/fs.h:499). 494 495 int mapping_tagged(struct address_space *mapping, int tag); 496 497 static inline void i_mmap_lock_write(struct address_space *mapping) 498 { 499 down_write(&mapping->i_mmap_rwsem); 500 } 501 502 static inline void i_mmap_unlock_write(struct address_space *mapping) 503 { This didn't happen on 4.2 + the XFS for-next code that was merged into 4.3-rc1, so it's come from changes somewhere else in the merge. I suspect either of these two commits: 46c043e mm: take i_mmap_lock in unmap_mapping_range() for DAX 8431729 dax: fix race between simultaneous faults as they both modified the i_mmap_lock usage for DAX page faults. Cheers, Dave. -- Dave Chinner david@fromorbit.com