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linux/fs/zonefs
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Damien Le Moal fe9da61ffc zonefs: fix synchronous direct writes to sequential files 
Commit 16d7fd3cfa ("zonefs: use iomap for synchronous direct writes")
changes zonefs code from a self-built zone append BIO to using iomap for
synchronous direct writes. This change relies on iomap submit BIO
callback to change the write BIO built by iomap to a zone append BIO.
However, this change overlooked the fact that a write BIO may be very
large as it is split when issued. The change from a regular write to a
zone append operation for the built BIO can result in a block layer
warning as zone append BIO are not allowed to be split.

WARNING: CPU: 18 PID: 202210 at block/bio.c:1644 bio_split+0x288/0x350
Call Trace:
? __warn+0xc9/0x2b0
? bio_split+0x288/0x350
? report_bug+0x2e6/0x390
? handle_bug+0x41/0x80
? exc_invalid_op+0x13/0x40
? asm_exc_invalid_op+0x16/0x20
? bio_split+0x288/0x350
bio_split_rw+0x4bc/0x810
? __pfx_bio_split_rw+0x10/0x10
? lockdep_unlock+0xf2/0x250
__bio_split_to_limits+0x1d8/0x900
blk_mq_submit_bio+0x1cf/0x18a0
? __pfx_iov_iter_extract_pages+0x10/0x10
? __pfx_blk_mq_submit_bio+0x10/0x10
? find_held_lock+0x2d/0x110
? lock_release+0x362/0x620
? mark_held_locks+0x9e/0xe0
__submit_bio+0x1ea/0x290
? __pfx___submit_bio+0x10/0x10
? seqcount_lockdep_reader_access.constprop.0+0x82/0x90
submit_bio_noacct_nocheck+0x675/0xa20
? __pfx_bio_iov_iter_get_pages+0x10/0x10
? __pfx_submit_bio_noacct_nocheck+0x10/0x10
iomap_dio_bio_iter+0x624/0x1280
__iomap_dio_rw+0xa22/0x18a0
? lock_is_held_type+0xe3/0x140
? __pfx___iomap_dio_rw+0x10/0x10
? lock_release+0x362/0x620
? zonefs_file_write_iter+0x74c/0xc80 [zonefs]
? down_write+0x13d/0x1e0
iomap_dio_rw+0xe/0x40
zonefs_file_write_iter+0x5ea/0xc80 [zonefs]
do_iter_readv_writev+0x18b/0x2c0
? __pfx_do_iter_readv_writev+0x10/0x10
? inode_security+0x54/0xf0
do_iter_write+0x13b/0x7c0
? lock_is_held_type+0xe3/0x140
vfs_writev+0x185/0x550
? __pfx_vfs_writev+0x10/0x10
? __handle_mm_fault+0x9bd/0x1c90
? find_held_lock+0x2d/0x110
? lock_release+0x362/0x620
? find_held_lock+0x2d/0x110
? lock_release+0x362/0x620
? __up_read+0x1ea/0x720
? do_pwritev+0x136/0x1f0
do_pwritev+0x136/0x1f0
? __pfx_do_pwritev+0x10/0x10
? syscall_enter_from_user_mode+0x22/0x90
? lockdep_hardirqs_on+0x7d/0x100
do_syscall_64+0x58/0x80

This error depends on the hardware used, specifically on the max zone
append bytes and max_[hw_]sectors limits. Tests using AMD Epyc machines
that have low limits did not reveal this issue while runs on Intel Xeon
machines with larger limits trigger it.

Manually splitting the zone append BIO using bio_split_rw() can solve
this issue but also requires issuing the fragment BIOs synchronously
with submit_bio_wait(), to avoid potential reordering of the zone append
BIO fragments, which would lead to data corruption. That is, this
solution is not better than using regular write BIOs which are subject
to serialization using zone write locking at the IO scheduler level.

Given this, fix the issue by removing zone append support and using
regular write BIOs for synchronous direct writes. This allows preseving
the use of iomap and having identical synchronous and asynchronous
sequential file write path. Zone append support will be reintroduced
later through io_uring commands to ensure that the needed special
handling is done correctly.

Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 16d7fd3cfa ("zonefs: use iomap for synchronous direct writes")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
 		2023-08-10 12:59:47 +09:00
..
Kconfig zonefs: select CONFIG_CRC32 2021-01-04 09:06:42 +09:00
Makefile zonefs: Reorganize code 2023-01-23 09:25:50 +09:00
file.c zonefs: fix synchronous direct writes to sequential files 2023-08-10 12:59:47 +09:00
super.c zonefs: fix synchronous direct writes to sequential files 2023-08-10 12:59:47 +09:00
sysfs.c zonefs: make kobj_type structure constant 2023-02-13 08:03:48 +09:00
trace.h zonefs: Separate zone information from inode information 2023-01-23 09:25:51 +09:00
zonefs.h zonefs: fix synchronous direct writes to sequential files 2023-08-10 12:59:47 +09:00