statmount: add a new supported_mask field

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Some of the fields in the statmount() reply can be optional. If the
kernel has nothing to emit in that field, then it doesn't set the flag
in the reply. This presents a problem: There is currently no way to
know what mask flags the kernel supports since you can't always count on
them being in the reply.

Add a new STATMOUNT_SUPPORTED_MASK flag and field that the kernel can
set in the reply. Userland can use this to determine if the fields it
requires from the kernel are supported. This also gives us a way to
deprecate fields in the future, if that should become necessary.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20250206-statmount-v2-1-6ae70a21c2ab@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

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Jeff Layton 2025-02-06 07:51:52 -05:00 • committed by Christian Brauner

parent 312994674e

commit 8f6116b5b7

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2 changed files with 26 additions and 1 deletions

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23

fs/namespace.c

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4

include/uapi/linux/mount.h

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