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Commit 02fac129 authored by Allison Henderson's avatar Allison Henderson Committed by Theodore Ts'o
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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: default avatarAllison Henderson <achender@linux.vnet.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 189e868f

fs/ext4/inode.c

+19 −0
Original line number Diff line number Diff line
@@ -2255,6 +2255,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping, 
	pgoff_t index;

	struct inode *inode = mapping->host;

	handle_t *handle;

	loff_t page_len;



	index = pos >> PAGE_CACHE_SHIFT;
@@ -2301,6 +2302,13 @@ retry: 
		 */

		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 @@ static int ext4_da_write_end(struct file *file, 
	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 @@ static int ext4_da_write_end(struct file *file, 
	}

	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;