Re: [PATCH v3 08/10] mm/shmem_luo: Allow preserving tmpfs files that are still linked

[sashiko-bot@kernel.org]

> Allow preserving tmpfs files that are still linked. To preserve any
> file, require permission to write to it and the file to be opened for
> reading, and reject append-only files.
> 
> shmem_luo already accepts any shmem file without links, which includes
> unlinked tmpfs files and files created with O_TMPFILE. Accepting linked
> files means that userspace doesn't have to unlink files to preserve them
> and can keep using them by path until the live update.
> 
> The path of the file isn't preserved. Like other files from tmpfs
> mounts, a linked file is retrieved onto a tmpfs mount chosen by
> userspace, which can then link it at the path it wants.
> 
> While a file is preserved, its size is frozen, so truncating it,
> fallocate() and writes past its end fail with -EPERM. For a linked file,
> [ ... ]
> and for immutable files.
> 
> Document the frozen size and the permission requirements.
> 
> Signed-off-by: David Matlack <dmatlack@google.com>

Sashiko has reviewed this patch and found no issues.

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