diff mbox series

[v2,2/6] shmem: return freed pages in shmem_free_swap

Message ID 20230919135536.2165715-3-da.gomez@samsung.com
State New
Headers
Series shmem: high order folios support in write path |

Commit Message

Daniel Gomez Sept. 19, 2023, 1:55 p.m. UTC 
  Both shmem_free_swap callers require to get the number of pages in the
folio after calling shmem_free_swap. Make shmem_free_swap return the
expected value directly and return 0 number of pages being freed
to avoid error handling in the external accounting.

Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
---
 mm/shmem.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

Comments

Matthew Wilcox Sept. 19, 2023, 2:56 p.m. UTC | #1 
On Tue, Sep 19, 2023 at 01:55:47PM +0000, Daniel Gomez wrote:
> +++ b/mm/shmem.c
> @@ -846,16 +846,18 @@ static void shmem_delete_from_page_cache(struct folio *folio, void *radswap)
>  /*
>   * Remove swap entry from page cache, free the swap and its page cache.
>   */
> -static int shmem_free_swap(struct address_space *mapping,
> +static long shmem_free_swap(struct address_space *mapping,
>  			   pgoff_t index, void *radswap)
>  {
>  	void *old;
>  
>  	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
>  	if (old != radswap)
> -		return -ENOENT;
> +		return 0;
> +
>  	free_swap_and_cache(radix_to_swp_entry(radswap));
> -	return 0;
> +
> +	return folio_nr_pages((struct folio *)radswap);
>  }

Oh my goodness.  I have led you astray; my apologies.

shmem_free_swap() is called when the 'folio' is NOT actually a folio.
It's an 'exceptional' / 'value' entry.  We can't do this.

Do we encode the size of the swap entry in the swp_entry_t or do
we have to get that information from the XArray (which no longer
knows it after we've stored a NULL there)?
diff mbox series

Patch

diff --git a/mm/shmem.c b/mm/shmem.c
index de0d0fa0349e..5c9e80207cbf 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -846,16 +846,18 @@  static void shmem_delete_from_page_cache(struct folio *folio, void *radswap)
 /*
  * Remove swap entry from page cache, free the swap and its page cache.
  */
-static int shmem_free_swap(struct address_space *mapping,
+static long shmem_free_swap(struct address_space *mapping,
 			   pgoff_t index, void *radswap)
 {
 	void *old;
 
 	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
 	if (old != radswap)
-		return -ENOENT;
+		return 0;
+
 	free_swap_and_cache(radix_to_swp_entry(radswap));
-	return 0;
+
+	return folio_nr_pages((struct folio *)radswap);
 }
 
 /*
@@ -1008,7 +1010,7 @@  static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 			if (xa_is_value(folio)) {
 				if (unfalloc)
 					continue;
-				nr_swaps_freed += !shmem_free_swap(mapping,
+				nr_swaps_freed += shmem_free_swap(mapping,
 							indices[i], folio);
 				continue;
 			}
@@ -1077,12 +1079,12 @@  static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 			if (xa_is_value(folio)) {
 				if (unfalloc)
 					continue;
-				if (shmem_free_swap(mapping, indices[i], folio)) {
+				nr_swaps_freed += shmem_free_swap(mapping, indices[i], folio);
+				if (!nr_swaps_freed) {
 					/* Swap was replaced by page: retry */
 					index = indices[i];
 					break;
 				}
-				nr_swaps_freed++;
 				continue;
 			}