CIFS: FS-Cache: Uncache unread pages in cifs_readpages() before freeing them

In cifs_readpages(), we may decide we don't want to read a page after all -
but the page may already have passed through fscache_read_or_alloc_pages() and
thus have marks and reservations set.  Thus we have to call
fscache_readpages_cancel() or fscache_uncache_page() on the pages we're
returning to clear the marks.

NFS, AFS and 9P should be unaffected by this as they call read_cache_pages()
which does the cleanup for you.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

3 files changed, 28 insertions, 0 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index eb955b525e55..7ddddf2e2504 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3254,6 +3254,9 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
         /*
          * Reads as many pages as possible from fscache. Returns -ENOBUFS
          * immediately if the cookie is negative
+         *
+         * After this point, every page in the list might have PG_fscache set,
+         * so we will need to clean that up off of every page we don't use.
          */
         rc = cifs_readpages_from_fscache(mapping->host, mapping, page_list,
                                          &num_pages);
@@ -3376,6 +3379,11 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
                 kref_put(&rdata->refcount, cifs_readdata_release);
         }
 
+        /* Any pages that have been shown to fscache but didn't get added to
+         * the pagecache must be uncached before they get returned to the
+         * allocator.
+         */
+        cifs_fscache_readpages_cancel(mapping->host, page_list);
         return rc;
 }
 
diff --git a/fs/cifs/fscache.c b/fs/cifs/fscache.c
index 2f4bc5a58054..b3258f35e88a 100644
--- a/fs/cifs/fscache.c
+++ b/fs/cifs/fscache.c
@@ -223,6 +223,13 @@ void __cifs_readpage_to_fscache(struct inode *inode, struct page *page)
                 fscache_uncache_page(CIFS_I(inode)->fscache, page);
 }
 
+void __cifs_fscache_readpages_cancel(struct inode *inode, struct list_head *pages)
+{
+        cifs_dbg(FYI, "%s: (fsc: %p, i: %p)\n",
+                 __func__, CIFS_I(inode)->fscache, inode);
+        fscache_readpages_cancel(CIFS_I(inode)->fscache, pages);
+}
+
 void __cifs_fscache_invalidate_page(struct page *page, struct inode *inode)
 {
         struct cifsInodeInfo *cifsi = CIFS_I(inode);
diff --git a/fs/cifs/fscache.h b/fs/cifs/fscache.h
index 63539323e0b9..24794b6cd8ec 100644
--- a/fs/cifs/fscache.h
+++ b/fs/cifs/fscache.h
@@ -54,6 +54,7 @@ extern int __cifs_readpages_from_fscache(struct inode *,
                                          struct address_space *,
                                          struct list_head *,
                                          unsigned *);
+extern void __cifs_fscache_readpages_cancel(struct inode *, struct list_head *);
 
 extern void __cifs_readpage_to_fscache(struct inode *, struct page *);
 
@@ -91,6 +92,13 @@ static inline void cifs_readpage_to_fscache(struct inode *inode,
                 __cifs_readpage_to_fscache(inode, page);
 }
 
+static inline void cifs_fscache_readpages_cancel(struct inode *inode,
+                                                 struct list_head *pages)
+{
+        if (CIFS_I(inode)->fscache)
+                return __cifs_fscache_readpages_cancel(inode, pages);
+}
+
 #else /* CONFIG_CIFS_FSCACHE */
 static inline int cifs_fscache_register(void) { return 0; }
 static inline void cifs_fscache_unregister(void) {}
@@ -131,6 +139,11 @@ static inline int cifs_readpages_from_fscache(struct inode *inode,
 static inline void cifs_readpage_to_fscache(struct inode *inode,
                         struct page *page) {}
 
+static inline void cifs_fscache_readpages_cancel(struct inode *inode,
+                                                 struct list_head *pages)
+{
+}
+
 #endif /* CONFIG_CIFS_FSCACHE */
 
 #endif /* _CIFS_FSCACHE_H */