Re: [PATCH v6 3/7] tmpfs: bump the mtime/ctime/iversion when page becomes writeable

Hugh Dickins
2023-07-26T01:39:42Z

On Tue, 25 Jul 2023, Jeff Layton wrote:

> Most filesystems that use the pagecache will update the mtime, ctime,
> and change attribute when a page becomes writeable. Add a page_mkwrite
> operation for tmpfs and just use it to bump the mtime, ctime and change
> attribute.
>
> This fixes xfstest generic/080 on tmpfs.

Huh. I didn't notice when this one crept into the multigrain series.

I'm inclined to NAK this patch: at the very least, it does not belong
in the series, but should be discussed separately.

Yes, tmpfs does not and never has used page_mkwrite, and gains some
performance advantage from that. Nobody has ever asked for this
change before, or not that I recall.

Please drop it from the series: and if you feel strongly, or know
strong reasons why tmpfs suddenly needs to use page_mkwrite now,
please argue them separately. To pass generic/080 is not enough.

Thanks,
Hugh

>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
> mm/shmem.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index b154af49d2df..654d9a585820 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2169,6 +2169,16 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
> return ret;
> }
>
> +static vm_fault_t shmem_page_mkwrite(struct vm_fault *vmf)
> +{
> + struct vm_area_struct *vma = vmf->vma;
> + struct inode *inode = file_inode(vma->vm_file);
> +
> + file_update_time(vma->vm_file);
> + inode_inc_iversion(inode);
> + return 0;
> +}
> +
> unsigned long shmem_get_unmapped_area(struct file *file,
> unsigned long uaddr, unsigned long len,
> unsigned long pgoff, unsigned long flags)
> @@ -4210,6 +4220,7 @@ static const struct super_operations shmem_ops = {
>
> static const struct vm_operations_struct shmem_vm_ops = {
> .fault = shmem_fault,
> + .page_mkwrite = shmem_page_mkwrite,
> .map_pages = filemap_map_pages,
> #ifdef CONFIG_NUMA
> .set_policy = shmem_set_policy,
> @@ -4219,6 +4230,7 @@ static const struct vm_operations_struct shmem_vm_ops = {
>
> static const struct vm_operations_struct shmem_anon_vm_ops = {
> .fault = shmem_fault,
> + .page_mkwrite = shmem_page_mkwrite,
> .map_pages = filemap_map_pages,
> #ifdef CONFIG_NUMA
> .set_policy = shmem_set_policy,
>
> --
> 2.41.0