ext4: Don't look at buffer_heads outside i_size.

Buffer heads outside i_size will be unmapped. So when we
are doing "walk_page_buffers" limit ourself to i_size.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Josef Bacik <jbacik@redhat.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
----

1 files changed, 16 insertions, 12 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ff2afc1909b3..b87b68cd3241 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2578,7 +2578,7 @@ static int ext4_da_writepage(struct page *page,
                  * all are mapped and non delay. We don't want to
                  * do block allocation here.
                  */
-                ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE,
+                ret = block_prepare_write(page, 0, len,
                                           noalloc_get_block_write);
                 if (!ret) {
                         page_bufs = page_buffers(page);
@@ -2600,7 +2600,7 @@ static int ext4_da_writepage(struct page *page,
                         return 0;
                 }
                 /* now mark the buffer_heads as dirty and uptodate */
-                block_commit_write(page, 0, PAGE_CACHE_SIZE);
+                block_commit_write(page, 0, len);
         }
 
         if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
@@ -3246,6 +3246,8 @@ static int ext4_normal_writepage(struct page *page,
 static int __ext4_journalled_writepage(struct page *page,
                                        struct writeback_control *wbc)
 {
+        loff_t size;
+        unsigned int len;
         struct address_space *mapping = page->mapping;
         struct inode *inode = mapping->host;
         struct buffer_head *page_bufs;
@@ -3253,14 +3255,17 @@ static int __ext4_journalled_writepage(struct page *page,
         int ret = 0;
         int err;
 
-        ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE,
-                                  noalloc_get_block_write);
+        size = i_size_read(inode);
+        if (page->index == size >> PAGE_CACHE_SHIFT)
+                len = size & ~PAGE_CACHE_MASK;
+        else
+                len = PAGE_CACHE_SIZE;
+        ret = block_prepare_write(page, 0, len, noalloc_get_block_write);
         if (ret != 0)
                 goto out_unlock;
 
         page_bufs = page_buffers(page);
-        walk_page_buffers(handle, page_bufs, 0, PAGE_CACHE_SIZE, NULL,
-                                                                bget_one);
+        walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
         /* As soon as we unlock the page, it can go away, but we have
          * references to buffers so we are safe */
         unlock_page(page);
@@ -3271,19 +3276,18 @@ static int __ext4_journalled_writepage(struct page *page,
                 goto out;
         }
 
-        ret = walk_page_buffers(handle, page_bufs, 0,
-                        PAGE_CACHE_SIZE, NULL, do_journal_get_write_access);
+        ret = walk_page_buffers(handle, page_bufs, 0, len, NULL,
+                                do_journal_get_write_access);
 
-        err = walk_page_buffers(handle, page_bufs, 0,
-                                PAGE_CACHE_SIZE, NULL, write_end_fn);
+        err = walk_page_buffers(handle, page_bufs, 0, len, NULL,
+                                write_end_fn);
         if (ret == 0)
                 ret = err;
         err = ext4_journal_stop(handle);
         if (!ret)
                 ret = err;
 
-        walk_page_buffers(handle, page_bufs, 0,
-                                PAGE_CACHE_SIZE, NULL, bput_one);
+        walk_page_buffers(handle, page_bufs, 0, len, NULL, bput_one);
         EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
         goto out;