diff mbox series

[v4,03/11] filemap: allocate mapping_min_order folios in the page cache

Message ID 20240425113746.335530-4-kernel@pankajraghav.com (mailing list archive)
State Superseded, archived
Headers show
Series enable bs > ps in XFS | expand

Commit Message

Pankaj Raghav (Samsung) April 25, 2024, 11:37 a.m. UTC 
From: Luis Chamberlain <mcgrof@kernel.org>

filemap_create_folio() and do_read_cache_folio() were always allocating
folio of order 0. __filemap_get_folio was trying to allocate higher
order folios when fgp_flags had higher order hint set but it will default
to order 0 folio if higher order memory allocation fails.

Supporting mapping_min_order implies that we guarantee each folio in the
page cache has at least an order of mapping_min_order. When adding new
folios to the page cache we must also ensure the index used is aligned to
the mapping_min_order as the page cache requires the index to be aligned
to the order of the folio.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Co-developed-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 mm/filemap.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

Comments

Hannes Reinecke April 25, 2024, 7:04 p.m. UTC | #1 
On 4/25/24 13:37, Pankaj Raghav (Samsung) wrote:
> From: Luis Chamberlain <mcgrof@kernel.org>
> 
> filemap_create_folio() and do_read_cache_folio() were always allocating
> folio of order 0. __filemap_get_folio was trying to allocate higher
> order folios when fgp_flags had higher order hint set but it will default
> to order 0 folio if higher order memory allocation fails.
> 
> Supporting mapping_min_order implies that we guarantee each folio in the
> page cache has at least an order of mapping_min_order. When adding new
> folios to the page cache we must also ensure the index used is aligned to
> the mapping_min_order as the page cache requires the index to be aligned
> to the order of the folio.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> Co-developed-by: Pankaj Raghav <p.raghav@samsung.com>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>   mm/filemap.c | 24 +++++++++++++++++-------
>   1 file changed, 17 insertions(+), 7 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
Darrick J. Wong April 26, 2024, 3:12 p.m. UTC | #2 
On Thu, Apr 25, 2024 at 01:37:38PM +0200, Pankaj Raghav (Samsung) wrote:
> From: Luis Chamberlain <mcgrof@kernel.org>
> 
> filemap_create_folio() and do_read_cache_folio() were always allocating
> folio of order 0. __filemap_get_folio was trying to allocate higher
> order folios when fgp_flags had higher order hint set but it will default
> to order 0 folio if higher order memory allocation fails.
> 
> Supporting mapping_min_order implies that we guarantee each folio in the
> page cache has at least an order of mapping_min_order. When adding new
> folios to the page cache we must also ensure the index used is aligned to
> the mapping_min_order as the page cache requires the index to be aligned
> to the order of the folio.

If we cannot find a folio of at least min_order size, what error is sent
back?

If the answer is "the same error that you get if we cannot allocate a
base page today (aka ENOMEM)", then I think I understand this enough to
say

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> Co-developed-by: Pankaj Raghav <p.raghav@samsung.com>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>  mm/filemap.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 30de18c4fd28..f0c0cfbbd134 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -858,6 +858,8 @@ noinline int __filemap_add_folio(struct address_space *mapping,
>  
>  	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
>  	VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
> +	VM_BUG_ON_FOLIO(folio_order(folio) < mapping_min_folio_order(mapping),
> +			folio);
>  	mapping_set_update(&xas, mapping);
>  
>  	if (!huge) {
> @@ -1895,8 +1897,10 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
>  		folio_wait_stable(folio);
>  no_page:
>  	if (!folio && (fgp_flags & FGP_CREAT)) {
> -		unsigned order = FGF_GET_ORDER(fgp_flags);
> +		unsigned int min_order = mapping_min_folio_order(mapping);
> +		unsigned int order = max(min_order, FGF_GET_ORDER(fgp_flags));
>  		int err;
> +		index = mapping_align_start_index(mapping, index);
>  
>  		if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
>  			gfp |= __GFP_WRITE;
> @@ -1936,7 +1940,7 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
>  				break;
>  			folio_put(folio);
>  			folio = NULL;
> -		} while (order-- > 0);
> +		} while (order-- > min_order);
>  
>  		if (err == -EEXIST)
>  			goto repeat;
> @@ -2425,13 +2429,16 @@ static int filemap_update_page(struct kiocb *iocb,
>  }
>  
>  static int filemap_create_folio(struct file *file,
> -		struct address_space *mapping, pgoff_t index,
> +		struct address_space *mapping, loff_t pos,
>  		struct folio_batch *fbatch)
>  {
>  	struct folio *folio;
>  	int error;
> +	unsigned int min_order = mapping_min_folio_order(mapping);
> +	pgoff_t index;
>  
> -	folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
> +	folio = filemap_alloc_folio(mapping_gfp_mask(mapping),
> +				    min_order);
>  	if (!folio)
>  		return -ENOMEM;
>  
> @@ -2449,6 +2456,8 @@ static int filemap_create_folio(struct file *file,
>  	 * well to keep locking rules simple.
>  	 */
>  	filemap_invalidate_lock_shared(mapping);
> +	/* index in PAGE units but aligned to min_order number of pages. */
> +	index = (pos >> (PAGE_SHIFT + min_order)) << min_order;
>  	error = filemap_add_folio(mapping, folio, index,
>  			mapping_gfp_constraint(mapping, GFP_KERNEL));
>  	if (error == -EEXIST)
> @@ -2509,8 +2518,7 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count,
>  	if (!folio_batch_count(fbatch)) {
>  		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
>  			return -EAGAIN;
> -		err = filemap_create_folio(filp, mapping,
> -				iocb->ki_pos >> PAGE_SHIFT, fbatch);
> +		err = filemap_create_folio(filp, mapping, iocb->ki_pos, fbatch);
>  		if (err == AOP_TRUNCATED_PAGE)
>  			goto retry;
>  		return err;
> @@ -3708,9 +3716,11 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
>  repeat:
>  	folio = filemap_get_folio(mapping, index);
>  	if (IS_ERR(folio)) {
> -		folio = filemap_alloc_folio(gfp, 0);
> +		folio = filemap_alloc_folio(gfp,
> +					    mapping_min_folio_order(mapping));
>  		if (!folio)
>  			return ERR_PTR(-ENOMEM);
> +		index = mapping_align_start_index(mapping, index);
>  		err = filemap_add_folio(mapping, folio, index, gfp);
>  		if (unlikely(err)) {
>  			folio_put(folio);
> -- 
> 2.34.1
> 
>
Pankaj Raghav (Samsung) April 28, 2024, 8:59 p.m. UTC | #3 
On Fri, Apr 26, 2024 at 08:12:43AM -0700, Darrick J. Wong wrote:
> On Thu, Apr 25, 2024 at 01:37:38PM +0200, Pankaj Raghav (Samsung) wrote:
> > From: Luis Chamberlain <mcgrof@kernel.org>
> > 
> > filemap_create_folio() and do_read_cache_folio() were always allocating
> > folio of order 0. __filemap_get_folio was trying to allocate higher
> > order folios when fgp_flags had higher order hint set but it will default
> > to order 0 folio if higher order memory allocation fails.
> > 
> > Supporting mapping_min_order implies that we guarantee each folio in the
> > page cache has at least an order of mapping_min_order. When adding new
> > folios to the page cache we must also ensure the index used is aligned to
> > the mapping_min_order as the page cache requires the index to be aligned
> > to the order of the folio.
> 
> If we cannot find a folio of at least min_order size, what error is sent
> back?
> 
> If the answer is "the same error that you get if we cannot allocate a
> base page today (aka ENOMEM)", then I think I understand this enough to
> say
> 
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>

Yes. We will get a ENOMEM if we cannot allocate min_order size folio. :)
Thanks!
> 
> --D
> 
> > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> > Co-developed-by: Pankaj Raghav <p.raghav@samsung.com>
> > Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> > ---
> >  mm/filemap.c | 24 +++++++++++++++++-------
> >  1 file changed, 17 insertions(+), 7 deletions(-)
> > 
> > diff --git a/mm/filemap.c b/mm/filemap.c
> > index 30de18c4fd28..f0c0cfbbd134 100644
> > --- a/mm/filemap.c
> > +++ b/mm/filemap.c
> > @@ -858,6 +858,8 @@ noinline int __filemap_add_folio(struct address_space *mapping,
> >  
> >  	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
> >  	VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
> > +	VM_BUG_ON_FOLIO(folio_order(folio) < mapping_min_folio_order(mapping),
> > +			folio);
> >  	mapping_set_update(&xas, mapping);
> >  
> >  	if (!huge) {
> > @@ -1895,8 +1897,10 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> >  		folio_wait_stable(folio);
> >  no_page:
> >  	if (!folio && (fgp_flags & FGP_CREAT)) {
> > -		unsigned order = FGF_GET_ORDER(fgp_flags);
> > +		unsigned int min_order = mapping_min_folio_order(mapping);
> > +		unsigned int order = max(min_order, FGF_GET_ORDER(fgp_flags));
> >  		int err;
> > +		index = mapping_align_start_index(mapping, index);
> >  
> >  		if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
> >  			gfp |= __GFP_WRITE;
> > @@ -1936,7 +1940,7 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> >  				break;
> >  			folio_put(folio);
> >  			folio = NULL;
> > -		} while (order-- > 0);
> > +		} while (order-- > min_order);
> >  
> >  		if (err == -EEXIST)
> >  			goto repeat;
> > @@ -2425,13 +2429,16 @@ static int filemap_update_page(struct kiocb *iocb,
> >  }
> >  
> >  static int filemap_create_folio(struct file *file,
> > -		struct address_space *mapping, pgoff_t index,
> > +		struct address_space *mapping, loff_t pos,
> >  		struct folio_batch *fbatch)
> >  {
> >  	struct folio *folio;
> >  	int error;
> > +	unsigned int min_order = mapping_min_folio_order(mapping);
> > +	pgoff_t index;
> >  
> > -	folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
> > +	folio = filemap_alloc_folio(mapping_gfp_mask(mapping),
> > +				    min_order);
> >  	if (!folio)
> >  		return -ENOMEM;
> >  
> > @@ -2449,6 +2456,8 @@ static int filemap_create_folio(struct file *file,
> >  	 * well to keep locking rules simple.
> >  	 */
> >  	filemap_invalidate_lock_shared(mapping);
> > +	/* index in PAGE units but aligned to min_order number of pages. */
> > +	index = (pos >> (PAGE_SHIFT + min_order)) << min_order;
> >  	error = filemap_add_folio(mapping, folio, index,
> >  			mapping_gfp_constraint(mapping, GFP_KERNEL));
> >  	if (error == -EEXIST)
> > @@ -2509,8 +2518,7 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count,
> >  	if (!folio_batch_count(fbatch)) {
> >  		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
> >  			return -EAGAIN;
> > -		err = filemap_create_folio(filp, mapping,
> > -				iocb->ki_pos >> PAGE_SHIFT, fbatch);
> > +		err = filemap_create_folio(filp, mapping, iocb->ki_pos, fbatch);
> >  		if (err == AOP_TRUNCATED_PAGE)
> >  			goto retry;
> >  		return err;
> > @@ -3708,9 +3716,11 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
> >  repeat:
> >  	folio = filemap_get_folio(mapping, index);
> >  	if (IS_ERR(folio)) {
> > -		folio = filemap_alloc_folio(gfp, 0);
> > +		folio = filemap_alloc_folio(gfp,
> > +					    mapping_min_folio_order(mapping));
> >  		if (!folio)
> >  			return ERR_PTR(-ENOMEM);
> > +		index = mapping_align_start_index(mapping, index);
> >  		err = filemap_add_folio(mapping, folio, index, gfp);
> >  		if (unlikely(err)) {
> >  			folio_put(folio);
> > -- 
> > 2.34.1
> > 
> >
diff mbox series

Patch

diff --git a/mm/filemap.c b/mm/filemap.c
index 30de18c4fd28..f0c0cfbbd134 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -858,6 +858,8 @@  noinline int __filemap_add_folio(struct address_space *mapping,
 
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 	VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
+	VM_BUG_ON_FOLIO(folio_order(folio) < mapping_min_folio_order(mapping),
+			folio);
 	mapping_set_update(&xas, mapping);
 
 	if (!huge) {
@@ -1895,8 +1897,10 @@  struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 		folio_wait_stable(folio);
 no_page:
 	if (!folio && (fgp_flags & FGP_CREAT)) {
-		unsigned order = FGF_GET_ORDER(fgp_flags);
+		unsigned int min_order = mapping_min_folio_order(mapping);
+		unsigned int order = max(min_order, FGF_GET_ORDER(fgp_flags));
 		int err;
+		index = mapping_align_start_index(mapping, index);
 
 		if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
 			gfp |= __GFP_WRITE;
@@ -1936,7 +1940,7 @@  struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 				break;
 			folio_put(folio);
 			folio = NULL;
-		} while (order-- > 0);
+		} while (order-- > min_order);
 
 		if (err == -EEXIST)
 			goto repeat;
@@ -2425,13 +2429,16 @@  static int filemap_update_page(struct kiocb *iocb,
 }
 
 static int filemap_create_folio(struct file *file,
-		struct address_space *mapping, pgoff_t index,
+		struct address_space *mapping, loff_t pos,
 		struct folio_batch *fbatch)
 {
 	struct folio *folio;
 	int error;
+	unsigned int min_order = mapping_min_folio_order(mapping);
+	pgoff_t index;
 
-	folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
+	folio = filemap_alloc_folio(mapping_gfp_mask(mapping),
+				    min_order);
 	if (!folio)
 		return -ENOMEM;
 
@@ -2449,6 +2456,8 @@  static int filemap_create_folio(struct file *file,
 	 * well to keep locking rules simple.
 	 */
 	filemap_invalidate_lock_shared(mapping);
+	/* index in PAGE units but aligned to min_order number of pages. */
+	index = (pos >> (PAGE_SHIFT + min_order)) << min_order;
 	error = filemap_add_folio(mapping, folio, index,
 			mapping_gfp_constraint(mapping, GFP_KERNEL));
 	if (error == -EEXIST)
@@ -2509,8 +2518,7 @@  static int filemap_get_pages(struct kiocb *iocb, size_t count,
 	if (!folio_batch_count(fbatch)) {
 		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
 			return -EAGAIN;
-		err = filemap_create_folio(filp, mapping,
-				iocb->ki_pos >> PAGE_SHIFT, fbatch);
+		err = filemap_create_folio(filp, mapping, iocb->ki_pos, fbatch);
 		if (err == AOP_TRUNCATED_PAGE)
 			goto retry;
 		return err;
@@ -3708,9 +3716,11 @@  static struct folio *do_read_cache_folio(struct address_space *mapping,
 repeat:
 	folio = filemap_get_folio(mapping, index);
 	if (IS_ERR(folio)) {
-		folio = filemap_alloc_folio(gfp, 0);
+		folio = filemap_alloc_folio(gfp,
+					    mapping_min_folio_order(mapping));
 		if (!folio)
 			return ERR_PTR(-ENOMEM);
+		index = mapping_align_start_index(mapping, index);
 		err = filemap_add_folio(mapping, folio, index, gfp);
 		if (unlikely(err)) {
 			folio_put(folio);