76fed01420
io_acct_set was enabled for raid0/raid5 io accounting. bios that contain md_io_acct are allocated in the i/o path. There isn't a good method to monitor if these bios are all finished and freed. In the takeover process, io_acct_set (which is used for bios with md_io_acct) need to be freed. However, if some bios finish after io_acct_set is freed, it may trigger the following panic: [ 6973.767999] RIP: 0010:mempool_free+0x52/0x80 [ 6973.786098] Call Trace: [ 6973.786549] md_end_io_acct+0x31/0x40 [ 6973.787227] blk_update_request+0x224/0x380 [ 6973.787994] blk_mq_end_request+0x1a/0x130 [ 6973.788739] blk_complete_reqs+0x35/0x50 [ 6973.789456] __do_softirq+0xd7/0x2c8 [ 6973.790114] ? sort_range+0x20/0x20 [ 6973.790763] run_ksoftirqd+0x2a/0x40 [ 6973.791400] smpboot_thread_fn+0xb5/0x150 [ 6973.792114] kthread+0x10b/0x130 [ 6973.792724] ? set_kthread_struct+0x50/0x50 [ 6973.793491] ret_from_fork+0x1f/0x40 Fix this by increasing and decreasing active_io for each bio with md_io_acct so that mddev_suspend() will wait until all bios from io_acct_set finish before freeing io_acct_set. Reported-by: Fine Fan <ffan@redhat.com> Signed-off-by: Xiao Ni <xni@redhat.com> Signed-off-by: Song Liu <song@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.