[PATCH 05/22] shmem: export shmem_get_folio

Christoph Hellwig
2024-02-19T06:27:46Z

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 | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

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
--
2.39.2