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Re: [PATCH 09/19] XFS: ensure xfs_file_*_read cannot deadlock in memory

To: NeilBrown <neilb@xxxxxxx>
Subject: Re: [PATCH 09/19] XFS: ensure xfs_file_*_read cannot deadlock in memory allocation.
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 16 Apr 2014 16:31:29 +1000
Cc: linux-mm@xxxxxxxxx, linux-nfs@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140416060459.GE15995@dastard>
References: <20140416033623.10604.69237.stgit@xxxxxxxxxxxxxx> <20140416040336.10604.90380.stgit@xxxxxxxxxxxxxx> <20140416060459.GE15995@dastard>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Apr 16, 2014 at 04:04:59PM +1000, Dave Chinner wrote:
> On Wed, Apr 16, 2014 at 02:03:36PM +1000, NeilBrown wrote:
> > xfs_file_*_read holds an inode lock while calling a generic 'read'
> > function.  These functions perform read-ahead and are quite likely to
> > allocate memory.
> 
> Yes, that's what reading data from disk requires.
> 
> > So set PF_FSTRANS to ensure they avoid __GFP_FS and so don't recurse
> > into a filesystem to free memory.
> 
> We already have that protection via the

Oops, stray paste. Ignore that comment.

-Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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