AFS: Don't put struct file on the stack

Don't put struct file on the stack as it takes up quite a lot of space
and violates lifetime rules for struct file.

Rather than calling afs_readpage() indirectly from the directory routines by
way of read_mapping_page(), split afs_readpage() to have afs_page_filler()
that's given a key instead of a file and call read_cache_page(), specifying the
new function directly.  Use it in afs_readpages() as well.

Also make use of this in afs_mntpt_check_symlink() too for the same reason.

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>

4 files changed, 41 insertions, 36 deletions

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index adc1cb771b57..b42d5cc1d6d2 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -189,13 +189,9 @@ static struct page *afs_dir_get_page(struct inode *dir, unsigned long index,
                                      struct key *key)
 {
         struct page *page;
-        struct file file = {
-                .private_data = key,
-        };
-
         _enter("{%lu},%lu", dir->i_ino, index);
 
-        page = read_mapping_page(dir->i_mapping, index, &file);
+        page = read_cache_page(dir->i_mapping, index, afs_page_filler, key);
         if (!IS_ERR(page)) {
                 kmap(page);
                 if (!PageChecked(page))
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 0df9bc2b724d..14d89fa58fee 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -121,34 +121,19 @@ static void afs_file_readpage_read_complete(struct page *page,
 #endif
 
 /*
- * AFS read page from file, directory or symlink
+ * read page from file, directory or symlink, given a key to use
  */
-static int afs_readpage(struct file *file, struct page *page)
+int afs_page_filler(void *data, struct page *page)
 {
-        struct afs_vnode *vnode;
-        struct inode *inode;
-        struct key *key;
+        struct inode *inode = page->mapping->host;
+        struct afs_vnode *vnode = AFS_FS_I(inode);
+        struct key *key = data;
         size_t len;
         off_t offset;
         int ret;
 
-        inode = page->mapping->host;
-
-        if (file) {
-                key = file->private_data;
-                ASSERT(key != NULL);
-        } else {
-                key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
-                if (IS_ERR(key)) {
-                        ret = PTR_ERR(key);
-                        goto error_nokey;
-                }
-        }
-
         _enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
 
-        vnode = AFS_FS_I(inode);
-
         BUG_ON(!PageLocked(page));
 
         ret = -ESTALE;
@@ -214,31 +199,56 @@ static int afs_readpage(struct file *file, struct page *page)
                 unlock_page(page);
         }
 
-        if (!file)
-                key_put(key);
         _leave(" = 0");
         return 0;
 
 error:
         SetPageError(page);
         unlock_page(page);
-        if (!file)
-                key_put(key);
-error_nokey:
         _leave(" = %d", ret);
         return ret;
 }
 
 /*
+ * read page from file, directory or symlink, given a file to nominate the key
+ * to be used
+ */
+static int afs_readpage(struct file *file, struct page *page)
+{
+        struct key *key;
+        int ret;
+
+        if (file) {
+                key = file->private_data;
+                ASSERT(key != NULL);
+                ret = afs_page_filler(key, page);
+        } else {
+                struct inode *inode = page->mapping->host;
+                key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
+                if (IS_ERR(key)) {
+                        ret = PTR_ERR(key);
+                } else {
+                        ret = afs_page_filler(key, page);
+                        key_put(key);
+                }
+        }
+        return ret;
+}
+
+/*
  * read a set of pages
  */
 static int afs_readpages(struct file *file, struct address_space *mapping,
                          struct list_head *pages, unsigned nr_pages)
 {
+        struct key *key = file->private_data;
         struct afs_vnode *vnode;
         int ret = 0;
 
-        _enter(",{%lu},,%d", mapping->host->i_ino, nr_pages);
+        _enter("{%d},{%lu},,%d",
+               key_serial(key), mapping->host->i_ino, nr_pages);
+
+        ASSERT(key != NULL);
 
         vnode = AFS_FS_I(mapping->host);
         if (vnode->flags & AFS_VNODE_DELETED) {
@@ -279,7 +289,7 @@ static int afs_readpages(struct file *file, struct address_space *mapping,
         }
 
         /* load the missing pages from the network */
-        ret = read_cache_pages(mapping, pages, (void *) afs_readpage, file);
+        ret = read_cache_pages(mapping, pages, afs_page_filler, key);
 
         _leave(" = %d [netting]", ret);
         return ret;
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index a10f2582844f..807f284cc75e 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -494,6 +494,7 @@ extern const struct file_operations afs_file_operations;
 
 extern int afs_open(struct inode *, struct file *);
 extern int afs_release(struct inode *, struct file *);
+extern int afs_page_filler(void *, struct page *);
 
 /*
  * flock.c
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index b3feddc4f7d6..a9e23039ea34 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -49,9 +49,6 @@ static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
  */
 int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
 {
-        struct file file = {
-                .private_data = key,
-        };
         struct page *page;
         size_t size;
         char *buf;
@@ -61,7 +58,8 @@ int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
                vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
 
         /* read the contents of the symlink into the pagecache */
-        page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, &file);
+        page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
+                               afs_page_filler, key);
         if (IS_ERR(page)) {
                 ret = PTR_ERR(page);
                 goto out;