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>

1 files changed, 23 insertions, 14 deletions

diff --git a/fs/romfs/inode.c b/fs/romfs/inode.c
index 8e51a2aaa977..60d2f822e87b 100644
--- 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);