linux-kernel - Re: [BUG] Reiserfs panic while running fsstress due to multiple truncate "safe links" for a file.

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Message-Id: <200611301144.59006.vs@namesys.com>
Date:	Thu, 30 Nov 2006 11:44:58 +0300
From:	"Vladimir V. Saveliev" <vs@...esys.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	reiserfs-list@...esys.com, suzuki <suzuki@...ux.vnet.ibm.com>,
	amitarora@...ibm.com, reiserfs-dev@...esys.com,
	lkml <linux-kernel@...r.kernel.org>, rdunlap@...otime.net
Subject: Re: [BUG] Reiserfs panic while running fsstress due to multiple	truncate "safe links" for a file.

Hello

On Tuesday 28 November 2006 05:57, suzuki wrote:
> Andrew Morton wrote:
> > On Mon, 27 Nov 2006 15:37:49 -0800
> > Suzuki <suzuki@...ibm.com> wrote:
> > 
> > 
> >>* Do not add save links for O_DIRECT writes.
> >>
> >>We add a save link for O_DIRECT writes to protect the i_size against the crashes before we actually finish the I/O. If we hit an -ENOSPC in aops->prepare_write(), we would do a truncate() to release the blocks which might have got initialized. Now the truncate would add another save link for the same inode causing a reiserfs panic for having multiple save links for the same inode.
> >>
> >>
> > 
> > 
> > OK...
> > 
> > But how does this patch fix it?  It removes a lot of code - how come we
> > don't need it any more?
> 
> We were adding save links for appending writes only. The links were 
> removed once we finish the write operation successfully.
> 
> Now we don't add the save links at all.
> 

The removed code was to return file to a length it had before direct writing far past end started 
if that direct write did not complete due to unclean shutdown.
I am not sure why it was needed. I guess that if long append (direct of bufferred) did not complete - it is ok if file becomes longer than it was before.

However, reiserfs seems to fail to update ondisk inode file size when appending big holes. The included patch fixes that.
Please, apply


From: Vladimir Saveliev <vs@...esys.com>

To write far past the end of a file reiserfs appends a hole first.
While the hole grows file size in ondisk inode has to be updated
so that in case of unclean shutdown it matches real file size.

Signed-off-by: Vladimir Saveliev <vs@...esys.com>



diff -puN fs/reiserfs/file.c~reiserfs-update-file-size-on-hole-creation fs/reiserfs/file.c
--- linux-2.6.19-rc6-mm2/fs/reiserfs/file.c~reiserfs-update-file-size-on-hole-creation	2006-11-29 17:54:03.000000000 +0300
+++ linux-2.6.19-rc6-mm2-vs/fs/reiserfs/file.c	2006-11-29 17:54:03.000000000 +0300
@@ -406,6 +406,8 @@ static int reiserfs_allocate_blocks_for_
 				   we restart it. This will also free the path. */
 				if (journal_transaction_should_end
 				    (th, th->t_blocks_allocated)) {
+					inode->i_size = cpu_key_k_offset(&key) +
+						(to_paste << inode->i_blkbits);
 					res =
 					    restart_transaction(th, inode,
 								&path);

_


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