mm: simplify generic_file_buffered_read_readpage

Stop passing pointless arguments, and return an int instead of a page
struct that contains either the passed in page, an ERR_PTR or NULL and
use goto labels to share common code.  Also rename the function to
filemap_readpage as it is a fairly generic wrapper around ->readpage
that isn't really specific to generic_file_buffered_read.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/mm/filemap.c b/mm/filemap.c
index d90614f501daa571b4f16b9ad0bbb546f7d90f12..2e997890cc81c2865dc713b5299fcdf2077aa275 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2168,59 +2168,53 @@ static int lock_page_for_iocb(struct kiocb *iocb, struct page *page)
                return lock_page_killable(page);
 }
 
-static struct page *
-generic_file_buffered_read_readpage(struct kiocb *iocb,
-                                   struct file *filp,
-                                   struct address_space *mapping,
-                                   struct page *page)
+static int filemap_readpage(struct kiocb *iocb, struct page *page)
 {
-       struct file_ra_state *ra = &filp->f_ra;
-       int error;
+       struct file *file = iocb->ki_filp;
+       int error = -EAGAIN;
 
        if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT)) {
                unlock_page(page);
-               put_page(page);
-               return ERR_PTR(-EAGAIN);
+               goto out_put_page;
        }
 
        /*
-        * A previous I/O error may have been due to temporary
-        * failures, eg. multipath errors.
-        * PG_error will be set again if readpage fails.
+        * A previous I/O error may have been due to temporary failures, e.g.
+        * multipath errors.  PG_error will be set again if readpage fails.
         */
        ClearPageError(page);
        /* Start the actual read. The read will unlock the page. */
-       error = mapping->a_ops->readpage(filp, page);
-
-       if (unlikely(error)) {
-               put_page(page);
-               return error != AOP_TRUNCATED_PAGE ? ERR_PTR(error) : NULL;
-       }
+       error = file->f_mapping->a_ops->readpage(file, page);
+       if (unlikely(error))
+               goto out_put_page;
 
        if (!PageUptodate(page)) {
                error = lock_page_for_iocb(iocb, page);
-               if (unlikely(error)) {
-                       put_page(page);
-                       return ERR_PTR(error);
-               }
+               if (unlikely(error))
+                       goto out_put_page;
+
                if (!PageUptodate(page)) {
                        if (page->mapping == NULL) {
                                /*
                                 * invalidate_mapping_pages got it
                                 */
                                unlock_page(page);
-                               put_page(page);
-                               return NULL;
+                               error = AOP_TRUNCATED_PAGE;
+                               goto out_put_page;
                        }
                        unlock_page(page);
-                       shrink_readahead_size_eio(ra);
-                       put_page(page);
-                       return ERR_PTR(-EIO);
+                       shrink_readahead_size_eio(&file->f_ra);
+                       error = -EIO;
+                       goto out_put_page;
                }
+
                unlock_page(page);
        }
+       return 0;
 
-       return page;
+out_put_page:
+       put_page(page);
+       return error;
 }
 
 static struct page *
@@ -2291,7 +2285,13 @@ page_not_up_to_date_locked:
                return page;
        }
 
-       return generic_file_buffered_read_readpage(iocb, filp, mapping, page);
+       error = filemap_readpage(iocb, page);
+       if (error) {
+               if (error == AOP_TRUNCATED_PAGE)
+                       return NULL;
+               return ERR_PTR(error);
+       }
+       return page;
 }
 
 static struct page *
@@ -2322,7 +2322,13 @@ generic_file_buffered_read_no_cached_page(struct kiocb *iocb,
                return error != -EEXIST ? ERR_PTR(error) : NULL;
        }
 
-       return generic_file_buffered_read_readpage(iocb, filp, mapping, page);
+       error = filemap_readpage(iocb, page);
+       if (error) {
+               if (error == AOP_TRUNCATED_PAGE)
+                       return NULL;
+               return ERR_PTR(error);
+       }
+       return page;
 }
 
 static int generic_file_buffered_read_get_pages(struct kiocb *iocb,