linux-ext4 - Re: [PATCH] ext4: Ensure zeroout blocks have no dirty metadata

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Date:	Tue, 15 Dec 2009 14:33:29 -0800
From:	Curt Wohlgemuth <curtw@...gle.com>
To:	Andreas Dilger <adilger@....com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: Ensure zeroout blocks have no dirty metadata

On Fri, Dec 11, 2009 at 3:27 PM, Andreas Dilger <adilger@....com> wrote:
> On 2009-12-11, at 15:01, Curt Wohlgemuth wrote:

>>
>> Good point, Andreas.  I changed this to send in the handle to
>> ext4_ext_zeroout().

> I was just thinking of checking EXT4_SB(inode->i_sb)->s_journal == NULL.  I
> also thought about checking EXT4_HAS_INCOMPAT_FEATURE(sb, NEEDS_RECOVERY),
> but I don't know if that is 100% safe (i.e. is it possible to mount such a
> filesystem with "norecovery"?).

Arggh.  There are too many ways to check the journal use/mode...  This
patch is considerably simpler.

=====================================================

This fixes a bug with no journal being used, in which new blocks returned
from an extent created with ext4_ext_zeroout() can have dirty metadata still
associated with them.

	Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>
---

This is for the problem I reported on 23 Nov ("Bug in extent zeroout: blocks
not marked as new").  I'm not seeing the corruption with this fix that I was
seeing without it.

diff -uprN orig/fs/ext4/extents.c new/fs/ext4/extents.c
--- orig/fs/ext4/extents.c	2009-12-09 15:09:25.000000000 -0800
+++ new/fs/ext4/extents.c	2009-12-15 13:26:29.000000000 -0800
@@ -2474,9 +2474,28 @@ static int ext4_ext_zeroout(struct inode
 		submit_bio(WRITE, bio);
 		wait_for_completion(&event);

-		if (test_bit(BIO_UPTODATE, &bio->bi_flags))
+		if (test_bit(BIO_UPTODATE, &bio->bi_flags)) {
+
 			ret = 0;
-		else {
+
+			/* On success, if there is no journal through which
+			 * metadata is committed, we need to insure all
+			 * metadata associated with each of these blocks is
+			 * unmapped. */
+			if (EXT4_SB(inode->i_sb)->s_journal == NULL) {
+				sector_t block = ee_pblock;
+
+				done = 0;
+				while (done < len) {
+					unmap_underlying_metadata(inode->i_sb->
+									s_bdev,
+								  block);
+
+					done++;
+					block++;
+				}
+			}
+		} else {
 			ret = -EIO;
 			break;
 		}
--
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