On 3/4/21 10:50 AM, Aurélien Aptel wrote:
From: Aurelien Aptel <aaptel@xxxxxxxx>
Similarly to NFS, CIFS flock() locks behave differently than the
standard. Document those differences.
Here is the rendered text:
CIFS details
In Linux kernels up to 5.4, flock() is not propagated over SMB. A file
with such locks will not appear locked for remote clients.
Since Linux 5.5, flock() locks are emulated with SMB byte-range locks
on the entire file. Similarly to NFS, this means that fcntl(2) and
flock() locks interact with one another. Another important side-effect
is that the locks are not advisory anymore: a write on a locked file
will always fail with EACCES. This difference originates from the de-
sign of locks in the SMB protocol, which provides mandatory locking se-
mantics. The nobrl mount option (see mount.cifs(8)) turns off fnctl(2)
and flock() lock propagation to remote clients and makes flock() locks
advisory again.
Signed-off-by: Aurelien Aptel <aaptel@xxxxxxxx>
Reviewed-By: Tom Talpey <tom@xxxxxxxxxx>
---
[...]
+This difference originates from the design of locks in the SMB
+protocol, which provides mandatory locking semantics. The
+.I nobrl
I agree with Tom. It's much easier to read if you just say that 'nobrl'
torns off the non-locale behaviour, and acts as 5.4 and earlier kernels.
Unless there's any subtlety that makes it different. Is there any?
BTW, you should use "semantic newlines":
$ man 7 man-pages |sed -n '/semantic newlines/,/^$/p'
Use semantic newlines
In the source of a manual page, new sentences should be
started on new lines, and long sentences should split into
lines at clause breaks (commas, semicolons, colons, and so
on). This convention, sometimes known as "semantic new-
lines", makes it easier to see the effect of patches, which
often operate at the level of individual sentences or sen-
tence clauses.
Thanks,
Alex
+mount option (see
+.BR mount.cifs (8))
+turns off
+.BR fnctl (2)
+and
+.BR flock ()
+lock propagation to remote clients and makes
+.BR flock ()
+locks advisory again.
.SH SEE ALSO
.BR flock (1),
.BR close (2),
--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/
