linux-ext4 - GFP_KERNEL in ext4 (was: [PATCH 4/4] Support discard if at least one underlying device supports it)

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Message-ID: <Pine.LNX.4.64.1007021605410.13662@hs20-bc2-1.build.redhat.com>
Date:	Fri, 2 Jul 2010 16:08:09 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Mike Snitzer <snitzer@...hat.com>
cc:	dm-devel@...hat.com, Alasdair G Kergon <agk@...hat.com>,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: GFP_KERNEL in ext4 (was: [PATCH 4/4] Support discard if at least
 one underlying device supports it)

> ---
>  include/linux/blkdev.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6.35-rc3-fast/include/linux/blkdev.h
> ===================================================================
> --- linux-2.6.35-rc3-fast.orig/include/linux/blkdev.h	2010-07-02 21:59:21.000000000 +0200
> +++ linux-2.6.35-rc3-fast/include/linux/blkdev.h	2010-07-02 21:59:37.000000000 +0200
> @@ -1021,7 +1021,7 @@ static inline int sb_issue_discard(struc
>  	block <<= (sb->s_blocksize_bits - 9);
>  	nr_blocks <<= (sb->s_blocksize_bits - 9);
>  	return blkdev_issue_discard(sb->s_bdev, block, nr_blocks, GFP_KERNEL,
> 				   BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
>  }
>  
>  extern int blk_verify_command(unsigned char *cmd, fmode_t has_write_perm);
> 

A note for ext4 developers: is that GFP_KERNEL safe? Can't it recurse back 
to ext4 and attempt to flush more data?

I'm not familiar enough with ext4 to declare that it is/isn't a bug, but 
it looks suspicious.

Mikulas
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