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[PATCH] retries in ext4_prepare_write() violate ordering requirements

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In journal=ordered or journal=data mode retry in ext4_prepare_write()
breaks the requirements of journaling of data with respect to metadata.
The fix is to call commit_write to commit allocated zero blocks before
retry.

Signed-off-by: Kirill Korotaev <dev@openvz.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ken Chen <kenneth.w.chen@intel.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andrey Savochkin 2006-12-06 20:37:36 -08:00 committed by Linus Torvalds
parent e92a4d595b
commit b46be05004
1 changed files with 75 additions and 10 deletions
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85
fs/ext4/inode.c
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@ -1147,37 +1147,102 @@ static int do_journal_get_write_access(handle_t *handle,
return ext4_journal_get_write_access(handle, bh);
}
/*
* The idea of this helper function is following:
* if prepare_write has allocated some blocks, but not all of them, the
* transaction must include the content of the newly allocated blocks.
* This content is expected to be set to zeroes by block_prepare_write().
* 2006/10/14 SAW
*/
static int ext4_prepare_failure(struct file *file, struct page *page,
unsigned from, unsigned to)
{
struct address_space *mapping;
struct buffer_head *bh, *head, *next;
unsigned block_start, block_end;
unsigned blocksize;
int ret;
handle_t *handle = ext4_journal_current_handle();
mapping = page->mapping;
if (ext4_should_writeback_data(mapping->host)) {
/* optimization: no constraints about data */
skip:
return ext4_journal_stop(handle);
}
head = page_buffers(page);
blocksize = head->b_size;
for ( bh = head, block_start = 0;
bh != head || !block_start;
block_start = block_end, bh = next)
{
next = bh->b_this_page;
block_end = block_start + blocksize;
if (block_end <= from)
continue;
if (block_start >= to) {
block_start = to;
break;
}
if (!buffer_mapped(bh))
/* prepare_write failed on this bh */
break;
if (ext4_should_journal_data(mapping->host)) {
ret = do_journal_get_write_access(handle, bh);
if (ret) {
ext4_journal_stop(handle);
return ret;
}
}
/*
* block_start here becomes the first block where the current iteration
* of prepare_write failed.
*/
}
if (block_start <= from)
goto skip;
/* commit allocated and zeroed buffers */
return mapping->a_ops->commit_write(file, page, from, block_start);
}
static int ext4_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
struct inode *inode = page->mapping->host;
int ret, needed_blocks = ext4_writepage_trans_blocks(inode);
int ret, ret2;
int needed_blocks = ext4_writepage_trans_blocks(inode);
handle_t *handle;
int retries = 0;
retry:
handle = ext4_journal_start(inode, needed_blocks);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
goto out;
}
if (IS_ERR(handle))
return PTR_ERR(handle);
if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
ret = nobh_prepare_write(page, from, to, ext4_get_block);
else
ret = block_prepare_write(page, from, to, ext4_get_block);
if (ret)
goto prepare_write_failed;
goto failure;
if (ext4_should_journal_data(inode)) {
ret = walk_page_buffers(handle, page_buffers(page),
from, to, NULL, do_journal_get_write_access);
if (ret)
/* fatal error, just put the handle and return */
journal_stop(handle);
}
prepare_write_failed:
if (ret)
ext4_journal_stop(handle);
return ret;
failure:
ret2 = ext4_prepare_failure(file, page, from, to);
if (ret2 < 0)
return ret2;
if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
goto retry;
out:
/* retry number exceeded, or other error like -EDQUOT */
return ret;
}