linux-ext4 - Re: [PATCH 1/2] [PATCH] ext4: Add inode to the orphan list during block allocation failure

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Message-ID: <20090605043117.GB4046@mit.edu>
Date:	Fri, 5 Jun 2009 00:31:17 -0400
From:	Theodore Tso <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/2] [PATCH] ext4: Add inode to the orphan list during
	block allocation failure

On Mon, Apr 06, 2009 at 12:05:09PM +0200, Jan Kara wrote:
> > I think this can be fixed by making sure that ext4_truncate() and
> > ext4_ext_truncate() calls ext4_orphan_del() in *all* of their error
> > paths.  That *should* the problem, since at the moment, it doesn't
> > look vmtruncate() will return without calling inode->i_op->truncate().
> > But could you double check this carefully?
>
>   Ah, OK, that should be fixed. But note that current ext4_setattr()
> does exactly the same thing on standard truncates - it adds inode to
> orphan list and calls inode_setattr() which end's up calling vmtruncate().

I finally had a chance to take a closer look at this.  ext4_setattr()
is safe, because it does this after calling inode_setattr():

	/* If inode_setattr's call to ext4_truncate failed to get a
	 * transaction handle at all, we need to clean up the in-core
	 * orphan list manually. */
	if (inode->i_nlink)
		ext4_orphan_del(NULL, inode);

So if we put the same thing into the ext4_write_begin() and
ext4_writeback_write_end() in these patches, it should be OK.  The key
is that if the inode is already is on the orphan list, it's harmless
to call ext4_orphan_add() --- and if the inode has already been
removed from the orphan list, it's harmless to call ext4_orphan_del()
on it.

					- Ted
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