[PATCH 05/20] shmem: export shmem_get_folio

[Christoph Hellwig <hch@lst.de>]

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 <hch@lst.de>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
---
 mm/shmem.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/mm/shmem.c b/mm/shmem.c
index ad533b2f0721a7..dae684cd3c99fb 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2137,12 +2137,27 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
 	return error;
 }
 
+/**
+ * shmem_get_folio - find and get a reference to a shmem folio.
+ * @inode:	inode to search
+ * @index:	the page index.
+ * @foliop:	pointer to the found folio if one was found
+ * @sgp:	SGP_* flags to control behavior
+ *
+ * Looks up the page cache entry at @inode & @index.
+ *
+ * If this function returns a folio, it is returned with an increased refcount.
+ *
+ * Return: The found folio, %NULL if SGP_READ or SGP_NOALLOC was passed in @sgp
+ * and no folio was found at @index, or an ERR_PTR() otherwise.
+ */
 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
-- 
2.39.2