[PATCH 3/3] fs: Pass a folio to page_put_link()

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

All callers now have a folio.  Pass it to page_put_link(), saving a
hidden call to compound_head().  Also add kernel-doc for page_get_link()
and page_put_link().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 fs/fuse/dir.c    |  2 +-
 fs/namei.c       | 30 +++++++++++++++++++++++++++---
 fs/nfs/symlink.c |  2 +-
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 83ac192e7fdd..33b82529cb6e 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1676,7 +1676,7 @@ static const char *fuse_get_link(struct dentry *dentry, struct inode *inode,
 		goto out_err;
 	}
 
-	set_delayed_call(callback, page_put_link, &folio->page);
+	set_delayed_call(callback, page_put_link, folio);
 
 	return folio_address(folio);
 
diff --git a/fs/namei.c b/fs/namei.c
index 8e82aa7ecb82..12d24f6da782 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5419,7 +5419,7 @@ static char *__page_get_link(struct dentry *dentry, struct inode *inode,
 		if (IS_ERR(folio))
 			return ERR_CAST(folio);
 	}
-	set_delayed_call(callback, page_put_link, &folio->page);
+	set_delayed_call(callback, page_put_link, folio);
 	BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
 	return folio_address(folio);
 }
@@ -5431,6 +5431,17 @@ const char *page_get_link_raw(struct dentry *dentry, struct inode *inode,
 }
 EXPORT_SYMBOL_GPL(page_get_link_raw);
 
+/**
+ * page_get_link() - An implementation of the get_link inode_operation.
+ * @dentry: The directory entry which is the symlink.
+ * @inode: The inode for the symlink.
+ * @callback: Used to drop the reference to the symlink.
+ *
+ * Filesystems which store their symlinks in the page cache should use
+ * this to implement the get_link() member of their inode_operations.
+ *
+ * Return: A pointer to the NUL-terminated symlink.
+ */
 const char *page_get_link(struct dentry *dentry, struct inode *inode,
 					struct delayed_call *callback)
 {
@@ -5440,12 +5451,25 @@ const char *page_get_link(struct dentry *dentry, struct inode *inode,
 		nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
 	return kaddr;
 }
-
 EXPORT_SYMBOL(page_get_link);
 
+/**
+ * page_put_link() - Drop the reference to the symlink.
+ * @arg: The folio which contains the symlink.
+ *
+ * This is used internally by page_get_link().  It is exported for use
+ * by filesystems which need to implement a variant of page_get_link()
+ * themselves.  Despite the apparent symmetry, filesystems which use
+ * page_get_link() do not need to call page_put_link().
+ *
+ * The argument, while it has a void pointer type, must be a pointer to
+ * the folio which was retrieved from the page cache.  The delayed_call
+ * infrastructure is used to drop the reference count once the caller
+ * is done with the symlink.
+ */
 void page_put_link(void *arg)
 {
-	put_page(arg);
+	folio_put(arg);
 }
 EXPORT_SYMBOL(page_put_link);
 
diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c
index 004a8f6c568e..58146e935402 100644
--- a/fs/nfs/symlink.c
+++ b/fs/nfs/symlink.c
@@ -63,7 +63,7 @@ static const char *nfs_get_link(struct dentry *dentry,
 		if (IS_ERR(folio))
 			return ERR_CAST(folio);
 	}
-	set_delayed_call(done, page_put_link, &folio->page);
+	set_delayed_call(done, page_put_link, folio);
 	return folio_address(folio);
 }
 
-- 
2.47.2