linux-ext4 - Re: [PATCH 2/2] [PATCH] ext4: truncate the file properly if we fail to copy data from userspace.

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Message-ID: <20090406100714.GC31189@duck.suse.cz>
Date:	Mon, 6 Apr 2009 12:07:14 +0200
From:	Jan Kara <jack@...e.cz>
To:	Theodore Tso <tytso@....edu>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH 2/2] [PATCH] ext4: truncate the file properly if we
	fail to copy data from userspace.

On Sat 04-04-09 23:22:11, Theodore Tso wrote:
> On Tue, Mar 31, 2009 at 02:59:26PM +0530, Aneesh Kumar K.V wrote:
> > In generic_perform_write if we fail to copy the user data we don't
> > update the inode->i_size. We should truncate the file in the above case
> > so that we don't have blocks allocated outside inode->i_size. Add
> > the inode to orphan list in the same transaction as block allocation
> > This ensures that if we crash in between the recovery would do the truncate.
> 
> Same problem as my comment in for the last patch; it seems rather
> dangerous to try to call ext4_orphan_add() outside of ext4_truncate().
> Can we instead call vmtruncate() inside the same transaction handle?
> i.e., figure out how many journal credits will be needed for the
> potential truncate, and add it to number of credits to reserve for the
> begin_write and/or write_end handle, and then call vmtruncate before
> calling ext4_journal_stop().  Can anyone see a problem with this
> approach?
  Just adding inode to orphan list seems more elegant to me and as I wrote
in my previous email, we already do it from a common path so if there are
bugs, we should fix them anyway ;).

									Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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