[PATCH 04/46] mm/memfd: make f_pos accesses atomic

[Rik van Riel]

On Tue, 2026-10-27 at 00:17 +0100, David Hildenbrand (Arm) wrote:
> From: Josef Bacik <josef at toxicpanda.com>
> 
> 
> Set the flag when the memfd is created.  As for any other regular
> file the
> lock is only taken if the file is reachable in more than one way, and
> nothing a memfd does in read or write waits for another operation on
> the
> same file.  This cannot be done for all alloc_file_pseudo() files:
> anon
> inode files such as eventfd are S_IFREG as well, and a blocked read
> holding
> ->f_pos_lock would lock out the write that is supposed to wake it.
> 
> Fix generated by an LLM and sent by Josef Bacik in private.
> 
> Fixes: 9183df25fe7b ("shm: add memfd_create() syscall")
> Cc: stable at vger.kernel.org
> Signed-off-by: Josef Bacik <josef at toxicpanda.com>
> [ david: minor description tweaks ]
> Signed-off-by: David Hildenbrand (Arm) <david at kernel.org>

Reviewed-by: Rik van Riel <riel at surriel.com>

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