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Date: Thu, 13 Mar 2003 19:09:08 +0000
From: Matthew Wilcox <willy@debian.org>
To: Alex Tomas <bzzz@tmi.comex.ru>
Cc: Andreas Dilger <adilger@clusterfs.com>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       ext2-devel@lists.sourceforge.net, Andrew Morton <akpm@digeo.com>
Subject: Re: [Ext2-devel] [PATCH] concurrent block allocation for ext2 against 2.5.64
Message-ID: <20030313190908.GC29631@parcelfarce.linux.theplanet.co.uk>
References: <m3el5bmyrf.fsf@lexa.home.net> <20030313103948.Z12806@schatzie.adilger.int> <m3d6kvhzuu.fsf@lexa.home.net>
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On Thu, Mar 13, 2003 at 09:43:05PM +0300, Alex Tomas wrote:
> 
> fs/attr.c:
>         if (ia_valid & ATTR_SIZE) {
>                 if (attr->ia_size == inode->i_size) {
>                         if (ia_valid == ATTR_SIZE)
>                                 goto out;       /* we can skip lock_kernel() */
>                 } else {
>                         lock_kernel();
>                         error = vmtruncate(inode, attr->ia_size);
>                         unlock_kernel();
>                         if (error)
>                                 goto out;
>                 }
>         }
> 
> so, all (!) truncates are serialized

This looks like a bug.  It should be safe to delete them.  Rationale:

 - Documentation/filesystems/Locking says ->truncate is called without the BKL.
 - This isn't the only place vmtruncate() is called.  Several of the callers
   do it without the BKL (eg xfs, cifs).
 - vmtruncate() appears to handle its own locking (mapping->i_shared_sem)

Comments?

-- 
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Do you think I want to have an academic debate on this subject?" -- Robert Fisk
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