romfs_readpage: don't report errors for pages beyond i_size

We zero-fill them like we are supposed to, and that's all fine.  It's
only an error if the 'romfs_copyfrom()' routine isn't able to fill the
data that is supposed to be there.

Most of the patch is really just re-organizing the code a bit, and using
separate variables for the error value and for how much of the page we
actually filled from the filesystem.

Reported-and-tested-by: Chris Fester <cfester@wms.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Matt Waddel <matt.waddel@freescale.com>
Cc: Greg Ungerer <gerg@snapgear.com>
Signed-of-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/romfs/inode.c b/fs/romfs/inode.c
index 8e51a2a..60d2f82 100644 (file)
--- a/fs/romfs/inode.c
+++ b/fs/romfs/inode.c
@@ -418,7 +418,8 @@ static int
 romfs_readpage(struct file *file, struct page * page)
 {
        struct inode *inode = page->mapping->host;
-       loff_t offset, avail, readlen;
+       loff_t offset, size;
+       unsigned long filled;
        void *buf;
        int result = -EIO;
 
@@ -430,21 +431,29 @@ romfs_readpage(struct file *file, struct page * page)
 
        /* 32 bit warning -- but not for us :) */
        offset = page_offset(page);
-       if (offset < i_size_read(inode)) {
-               avail = inode->i_size-offset;
-               readlen = min_t(unsigned long, avail, PAGE_SIZE);
-               if (romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen) == readlen) {
-                       if (readlen < PAGE_SIZE) {
-                               memset(buf + readlen,0,PAGE_SIZE-readlen);
-                       }
-                       SetPageUptodate(page);
-                       result = 0;
+       size = i_size_read(inode);
+       filled = 0;
+       result = 0;
+       if (offset < size) {
+               unsigned long readlen;
+
+               size -= offset;
+               readlen = size > PAGE_SIZE ? PAGE_SIZE : size;
+
+               filled = romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen);
+
+               if (filled != readlen) {
+                       SetPageError(page);
+                       filled = 0;
+                       result = -EIO;
                }
        }
-       if (result) {
-               memset(buf, 0, PAGE_SIZE);
-               SetPageError(page);
-       }
+
+       if (filled < PAGE_SIZE)
+               memset(buf + filled, 0, PAGE_SIZE-filled);
+
+       if (!result)
+               SetPageUptodate(page);
        flush_dcache_page(page);
 
        unlock_page(page);