udev's block device locking protocol has one pitfall not even the
example in the documentation got right so far (even though this is
explained in all detail above): udev's rescanning is only triggered when
an fd that is opened for writing is closed. This means that if a
separate locking fd is opened on a block device – one that is maintained
independently of the fd actually used for writing – it must be opened for
writing too, so that closing the lock definitely triggers a rescan. This
matters in cases where the lock fd is kept for longer than the fd used
for writing to disk. (Because otherwise udev might get the
IN_CLOSE_WRITE event, but when it tries to rescan will find the device
locked, and never retry because no IN_CLOSE_WRITE is triggred anymore.)
Let's fix that across the codebase, at 4 places:
1. in makefs (a lock fd is kept, and mkfs then invoked as child, which
uses a different fd, and the lock fd is closed only once the child
died)
2. in udevadm lock (embarassing!): which is intended to be used to wrap tools
that modify disk contents, very similar to the makefs case. The lock
is also kept until after the tool exited.
3. In storagetm: the kernel nvme-tcp layer writes to the device
directly, we just keep a lock fd.
4. the example in BLOCK_DEVICE_LOCKING.md
Add a new `MakeFilesystemFlags` enum and use it to replace the existing
`quiet` and `discard` booleans on `make_filesystem()`.
Update the callers. While we're doing that, consolidate some duplicated
logic in systemd-repart.
Signed-off-by: Allison Karlitskaya <allison.karlitskaya@redhat.com>
This commit cleans up the includes for all the small tools across
the tree.
A few cases of returning EXIT_SUCCESS are replaced with returning
0 to avoid including <stdlib.h>.
Split out of #37344.
Let's move some logic from _DEFINE_MAIN_FUNCTION() and other places
in main-func.h into functions that we implement in main-func.c to
allow moving some included headers from the header to the .c file.
To resolve conflict with sys/mount.h and linux/mount.h or linux/fs.h.
The conflict between sys/mount.h and linux/mount.h is resolved in
glibc-2.37 (774058d72942249f71d74e7f2b639f77184160a6), but our baseline
is still glibc-2.31. Also, even with the version or newer, still
sys/mount.h conflicts with linux/fs.h, which is included by
linux/btrfs.h.
This introduces our own implementation of sys/mount.h, that can be
simultaneously included with linux/mount.h and linux/fs.h. This also
imports linux/fs.h, linux/mount.h, and several other dependent headers.
The introduced sys/mount.h header itself may not be enough simple, but
by using the header, we can drop most of workarounds in other source files.
Yu Watanabe
Lennart Poettering
Allison Karlitskaya
Daan De Meyer
Zbigniew Jędrzejewski-Szmek