[RFC PATCH 4/9] shmem: exit shmem_get_folio_gfp() if block is uptodate

[Daniel Gomez]

When we get a folio from the page cache with filemap_get_entry() and
is uptodate we exit from shmem_get_folio_gfp(). Replicate the same
behaviour if the block is uptodate in the index we are operating on.

Signed-off-by: Daniel Gomez <da.gomez@xxxxxxxxxxx>
---
 mm/shmem.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 3bddf7a89c18..614cda767298 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -256,6 +256,16 @@ static inline bool shmem_is_any_uptodate(struct folio *folio)
 	return folio_test_uptodate(folio);
 }
 
+static inline bool shmem_is_block_uptodate(struct folio *folio,
+					   unsigned int block)
+{
+	struct shmem_folio_state *sfs = folio->private;
+
+	if (folio_test_large(folio) && sfs)
+		return sfs_is_block_uptodate(sfs, block);
+	return folio_test_uptodate(folio);
+}
+
 static void shmem_set_range_uptodate(struct folio *folio, size_t off,
 				     size_t len)
 {
@@ -2143,7 +2153,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
 		}
 		if (sgp == SGP_WRITE)
 			folio_mark_accessed(folio);
-		if (folio_test_uptodate(folio))
+		if (shmem_is_block_uptodate(folio, index - folio_index(folio)))
 			goto out;
 		/* fallocated folio */
 		if (sgp != SGP_READ)
-- 
2.43.0