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Message-ID: <455492F9.7080300@openvz.org>
Date: Fri, 10 Nov 2006 17:55:53 +0300
From: Kirill Korotaev <dev@...nvz.org>
To: Andrew Morton <akpm@...l.org>, ext2-devel@...ts.sourceforge.net,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
devel@...nvz.org
CC: Andrey Savochkin <saw@...ru>, sct@...hat.com, adilger@...sterfs.com
Subject: [PATCH] retries in ext3_prepare_write() violate ordering requirements
in journal=ordered or journal=data mode retry in ext3_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.
Author: Andrey Savochkin <saw@...ru>
Signed-Off-By: Kirill Korotaev <dev@...nvz.org>
--- ./fs/ext3/inode.c.ext3pw 2006-11-08 17:44:14.000000000 +0300
+++ ./fs/ext3/inode.c 2006-11-08 17:48:59.000000000 +0300
@@ -1148,37 +1148,89 @@ static int do_journal_get_write_access(h
return ext3_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 ext3_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;
+
+ mapping = page->mapping;
+ if (ext3_should_writeback_data(mapping->host)) {
+ /* optimization: no constraints about data */
+skip:
+ ext3_journal_stop(ext3_journal_current_handle());
+ return 0;
+ }
+
+ 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))
+ break;
+ }
+ if (block_start <= from)
+ goto skip;
+
+ /* commit allocated and zeroed buffers */
+ return mapping->a_ops->commit_write(file, page, from, block_start);
+}
+
static int ext3_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
struct inode *inode = page->mapping->host;
- int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
+ int ret, ret2;
+ int needed_blocks = ext3_writepage_trans_blocks(inode);
handle_t *handle;
int retries = 0;
retry:
handle = ext3_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) && ext3_should_writeback_data(inode))
ret = nobh_prepare_write(page, from, to, ext3_get_block);
else
ret = block_prepare_write(page, from, to, ext3_get_block);
if (ret)
- goto prepare_write_failed;
+ goto failure;
if (ext3_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)
- ext3_journal_stop(handle);
+ return ret;
+
+failure:
+ ret2 = ext3_prepare_failure(file, page, from, to);
+ if (ret2 < 0)
+ return ret2;
if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
goto retry;
-out:
+ /* retry number exceeded, or other error like -EDQUOT */
return ret;
}
-
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