Re: [PATCH v3 07/10] mm/shmem_luo: Retrieve tmpfs files onto a tmpfs mount chosen by userspace

[sashiko-bot@kernel.org]

> Retrieve files that were preserved from a tmpfs mount onto a tmpfs mount
> chosen by userspace, instead of as memfds on the internal tmpfs mount.
> Add struct liveupdate_shmem_retrieve_arg, which userspace passes as the
> retrieve argument of LIVEUPDATE_SESSION_RETRIEVE_FD to choose the mount.
> Record which mount a file was on with a new SHMEM_LUO_FLAG_TMPFS flag in
> struct shmem_luo_ser, based on the superblock of the file.
> 
> shmem_luo already accepts unlinked tmpfs files, such as files created
> with O_TMPFILE, and a following commit also accepts linked ones. The
> mount such a file was on doesn't exist in the new kernel, and userspace
> may want to put the file elsewhere anyway.
> 
> Model struct liveupdate_shmem_retrieve_arg on open(): The kernel creates
> a new file as if by openat(dirfd, ".", O_TMPFILE | flags, mode), so the
> file gets the owner, permission checks and security labels of any new
> [ ... ]
> 
> Like the other failures before the folios are restored, problems with
> the argument and with creating the file can be retried.
> 
> Signed-off-by: David Matlack <dmatlack@google.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261103010216.3447716-1-dmatlack@google.com?part=7