Re: [PATCH] fcntl.2, read.2, write.2: document "Lost locks" as cause for EIO.

On 12/18/2017 10:45 PM, NeilBrown wrote:

On Mon, Dec 18 2017, Michael Kerrisk (man-pages) wrote:

quoted

Hello Neil

There's a piece of your patch I don't understand. Please see below.

On 12/13/2017 05:19 AM, NeilBrown wrote:

quoted

If an advisory lock is lost, then read/write requests on any
affected file descriptor can return EIO - for NFSv4 at least.

Signed-off-by: NeilBrown <neilb-IBi9RG/b67k@public.gmane.org>
---
 man2/fcntl.2 | 24 ++++++++++++++++++++++++
 man2/read.2  |  9 +++++++++
 man2/write.2 |  9 +++++++++
 3 files changed, 42 insertions(+)

diff --git a/man2/fcntl.2 b/man2/fcntl.2
index 67642384154c..6e6e26f66aa0 100644
--- a/man2/fcntl.2
+++ b/man2/fcntl.2

@@ -669,6 +669,30 @@ and
 Mandatory locking is not specified by POSIX.
 Some other systems also support mandatory locking,
 although the details of how to enable it vary across systems.
+.SS Lost locks
+When an advisory lock is obtained on a networked filesystem such as
+NFS it is possible that the lock might get lost.
+This may happen due to administrative action on the server, or due to a
+network partition which lasts long enough for the server to assume

What does "network partition which lasts long enough" mean?
I think this perhaps needs to be clarified a little. At least,
I don't understand it.

"network partition" is a term using the NFS RFCs for any situation that
that results in the server and client not being able to communicate
(that are partitioned, one from the other?  There is partition (wall)
between them?  They are in separate partitions?).
I can see how the meaning might not be obvious if you hadn't come across
it before.

If we change "network partition" to "loss of connectivity", would that
make it clear.  Is "loss of network connectivity with the server" too
verbose?

Thanks, Neil. I've applied your patch and added the words "loss of network
connectivity with the server".

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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