HOWTO: Add note/exception on allow_mounted_write=
allow_mounted_write= is useful on Linux, but some platforms
just return some error on open(2) for mounted devices.
# uname
Linux
# mkfs.ext4 /dev/loop0 > /dev/null
mke2fs 1.43.3 (04-Sep-2016)
# mount /dev/loop0 /mnt
# mount | grep /dev/loop0
/dev/loop0 on /mnt type ext4 (rw,relatime,seclabel,data=ordered)
# fio --name=xxxxx --ioengine=sync --rw=write --bs=32k --size=1m --filename=/dev/loop0
xxxxx: (g=0): rw=write, bs=32.0KiB-32.0KiB,32.0KiB-32.0KiB,32.0KiB-32.0KiB, ioengine=sync, iodepth=1
fio-2.18-21-gca205
fio: /dev/loop0 appears mounted, and 'allow_mounted_write' isn't set. Aborting.
Run status group 0 (all jobs):
# fio --name=xxxxx --ioengine=sync --rw=write --bs=32k --size=1m --filename=/dev/loop0 --allow_mounted_write=1 > /dev/null; echo $?
0
# uname
FreeBSD
# newfs /dev/da1 > /dev/null
# mount /dev/da1 /mnt
# mount | grep /dev/da1
/dev/da1 on /mnt (ufs, local)
# fio --name=xxxxx --ioengine=sync --rw=write --bs=32k --size=1m --filename=/dev/da1 --allow_mounted_write=1
fio: this platform does not support process shared mutexes, forcing use of threads. Use the 'thread' option to get rid of this warning.
xxxxx: (g=0): rw=write, bs=32.0KiB-32.0KiB,32.0KiB-32.0KiB,32.0KiB-32.0KiB, ioengine=sync, iodepth=1
fio-2.18-21-gca205
Starting 1 thread
fio: failed opening chardev /dev/da1 for size check
file:filesetup.c:654, func=open(/dev/da1), error=Operation not permitted
fio: pid=0, err=1/file:filesetup.c:654, func=open(/dev/da1), error=Operation not permitted
Run status group 0 (all jobs)
Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Jens Axboe <axboe@fb.com>