24.10.2017 11:33, Lennart Poettering пишет: > On Fr, 13.10.17 01:01, Akira Hayakawa (ruby.w...@gmail.com) wrote: > >> I have a device /dev/sdb1 and let's trace the block request by blktrace >> >> $ sudo blktrace -d /dev/sdb1 >> >> When I write 4KB using dd >> $ sudo dd if=/dev/zero of=/dev/sdb1 oflag=direct bs=4k count=1 >> >> The block trace (after blkparsed) is write request as expected >> 8,17 2 2 0.000003171 5930 Q WS 2048 + 8 [dd] >> >> followed by a unexpected read from systemd-udevd >> 8,17 7 2 0.001755563 5931 Q R 2048 + 8 [systemd-udevd] >> >> My first question is what is: this read request? >> >> And I want to stop the read request because it makes it difficult to test >> kernel code. >> So the second question is: how can I stop the read request? > > If you want exclusive access to a block device and don't want udev to > step in, then simply take a BSD file lock on it (i.e. flock(2)), and > udev won't probe it. >
How do you take exclusive lock on device that does not even exist yet (like in case of dmsetup create)? _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
