Re: [PATCH v3 2/2] mm/filemap: do not count FAULT_FLAG_TRIED retries as mmap hits

[Jan Kara]

On Tue 28-04-26 01:59:44, fujunjie wrote:
> A fault that starts synchronous mmap readahead can return VM_FAULT_RETRY
> after dropping mmap_lock.  The retry may then map the folio brought in
> by that same miss.
> 
> Do not let this retry decrement mmap_miss.  The retry still maps the
> folio from the page cache; it just does not count as a useful mmap
> readahead hit.
> 
> Signed-off-by: fujunjie <fujunjie1@xxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  mm/filemap.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 543e51c32397..86a46a61eac8 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3933,6 +3933,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
>  		 * we can stop read-ahead.
>  		 */
>  		if ((map_ret & VM_FAULT_NOPAGE) &&
> +		    !(vmf->flags & FAULT_FLAG_TRIED) &&
>  		    !folio_test_workingset(folio)) {
>  			unsigned short mmap_miss;
>  
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR