Re: [PATCH v3 1/2] mm/filemap: count only the faulting address as a mmap hit

Re: [PATCH v3 1/2] mm/filemap: count only the faulting address as a mmap hit

[Vishal Moola]

On Tue, Apr 28, 2026 at 01:59:43AM +0000, fujunjie wrote:
> filemap_map_pages() reduces file->f_ra.mmap_miss when fault-around maps
> folios that are already present in the page cache.  That hit accounting
> is too generous because fault-around can install PTEs around the
> faulting address even though the fault only proves that the faulting
> address was accessed.
> 
> Move the mmap_miss update back into filemap_map_pages(), drop the
> mmap_miss argument from the helper functions, and decrement mmap_miss
> only when the helper return value shows that the faulting address was
> mapped.  Keep the existing workingset-folio behavior unchanged.
> 
> Signed-off-by: fujunjie <fujunjie1@qq.com>
> ---

Reviewed-by: Vishal Moola <vishal.moola@gmail.com>

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

[Vishal Moola]

On Tue, Apr 28, 2026 at 01:59:44AM +0000, 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@qq.com>
> ---

Reviewed-by: Vishal Moola <vishal.moola@gmail.com>