[05/22] shmem: export shmem_get_folio

Commit Message

Christoph Hellwig Feb. 19, 2024, 6:27 a.m. UTC

Export shmem_get_folio as a slightly lower-level variant of
shmem_read_folio_gfp.  This will be useful for XFS xfile use cases
that want to pass SGP_NOALLOC or get a locked page, which the thin
shmem_read_folio_gfp wrapper can't provide.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Matthew Wilcox (Oracle) <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
---
 mm/shmem.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

Patch

diff --git a/mm/shmem.c b/mm/shmem.c
index ad533b2f0721a7..aeb1fd19ea3f72 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2137,12 +2137,32 @@  static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
 	return error;
 }
 
+/**
+ * shmem_get_folio - find, and lock a shmem folio.
+ * @inode:	inode to search
+ * @index:	the page index.
+ * @foliop:	pointer to the folio if found
+ * @sgp:	SGP_* flags to control behavior
+ *
+ * Looks up the page cache entry at @inode & @index.  If a folio is
+ * present, it is returned locked with an increased refcount.
+ *
+ * When no folio is found, the behavior depends on @sgp:
+ *  - for SGP_READ, *foliop is %NULL and 0 is returned
+ *  - for SGP_NOALLOC, *foliop is %NULL and -ENOENT is returned
+ *  - for all other flags a new folio is allocated, inserted into the
+ *    page cache and returned locked in @foliop.
+ *
+ * Context: May sleep.
+ * Return: 0 if successful, else a negative error code.
+ */
 int shmem_get_folio(struct inode *inode, pgoff_t index, struct folio **foliop,
 		enum sgp_type sgp)
 {
 	return shmem_get_folio_gfp(inode, index, foliop, sgp,
 			mapping_gfp_mask(inode->i_mapping), NULL, NULL);
 }
+EXPORT_SYMBOL_GPL(shmem_get_folio);
 
 /*
  * This is like autoremove_wake_function, but it removes the wait queue