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

[David Matlack <dmatlack@google.com>]

On 2026-11-04 05:45 PM, Pratyush Yadav wrote:
[...]
> > + * Preserving a file requires it to be opened for reading, since the retrieved
> > + * file can be read. It also requires permission to write to the file, since
> > + * preserving it affects all of its users, as described below. But the file
> > + * doesn't need to be opened for writing. For example, a binary that is being
> > + * executed can be preserved through a read-only file descriptor. The owner of
> 
> Why are you talking about preserving binaries being executed? Seems
> oddly specific. I didn't know that was a use case we cared about.

It's the reason the check looks at permission on the inode instead of
requiring an fd opened for writing: a running binary can't be opened for
writing (-ETXTBSY), so requiring a writable fd would make it impossible
to preserve. Preserving binaries is a use case we care about, e.g. to
carry over the binaries of services across a Live Update. I'll keep the
comment shorter and more general in v4.