ext4: fix partial page writes
While running extended fsx tests to verify the preceeding patches,
a similar bug was also found in the write operation
When ever a write operation begins or ends in a hole,
or extends EOF, the partial page contained in the hole
or beyond EOF needs to be zeroed out.
To correct this the new ext4_discard_partial_page_buffers_no_lock
routine is used to zero out the partial page, but only for buffer
heads that are already unmapped.
Signed-off-by: Allison Henderson <achender@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f86b149..6ecc939 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2255,6 +2255,7 @@
pgoff_t index;
struct inode *inode = mapping->host;
handle_t *handle;
+ loff_t page_len;
index = pos >> PAGE_CACHE_SHIFT;
@@ -2301,6 +2302,13 @@
*/
if (pos + len > inode->i_size)
ext4_truncate_failed_write(inode);
+ } else {
+ page_len = pos & (PAGE_CACHE_SIZE - 1);
+ if (page_len > 0) {
+ ret = ext4_discard_partial_page_buffers_no_lock(handle,
+ inode, page, pos - page_len, page_len,
+ EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED);
+ }
}
if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
@@ -2343,6 +2351,7 @@
loff_t new_i_size;
unsigned long start, end;
int write_mode = (int)(unsigned long)fsdata;
+ loff_t page_len;
if (write_mode == FALL_BACK_TO_NONDELALLOC) {
if (ext4_should_order_data(inode)) {
@@ -2391,6 +2400,16 @@
}
ret2 = generic_write_end(file, mapping, pos, len, copied,
page, fsdata);
+
+ page_len = PAGE_CACHE_SIZE -
+ ((pos + copied - 1) & (PAGE_CACHE_SIZE - 1));
+
+ if (page_len > 0) {
+ ret = ext4_discard_partial_page_buffers_no_lock(handle,
+ inode, page, pos + copied - 1, page_len,
+ EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED);
+ }
+
copied = ret2;
if (ret2 < 0)
ret = ret2;