linux-ext4 - Re: [PATCH 0/2] 32/64 bit llseek hashes

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Message-ID: <4E4A5AD5.3040507@itwm.fraunhofer.de>
Date:	Tue, 16 Aug 2011 13:56:05 +0200
From:	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>
To:	linux-nfs@...r.kernel.org, linux-ext4@...r.kernel.org
CC:	hch@...radead.org, yong.fan@...mcloud.com,
	linux-fsdevel@...r.kernel.org, tytso@....edu, adilger@...mcloud.com
Subject: Re: [PATCH 0/2] 32/64 bit llseek hashes

I'm really sorry for this patch spam :( I just accidentally hit the 
enter key too early here and so patches go into this series, which
weren't supposed to get in here :(

On 08/16/2011 01:25 PM, Bernd Schubert wrote:
> With the ext3/ext4 directory index implementation hashes are used to specify
> offsets for llseek(). For compatibility with NFSv2 and 32-bit user space
> on 64-bit systems (kernel space) ext3/ext4 currently only return 32-bit
> hashes and therefore the probability of hash collisions for larger directories
> is rather high. As recently reported on the NFS mailing list that theoretical
> problem also happens on real systems:
> http://comments.gmane.org/gmane.linux.nfs/40863
>
> The following series adds two new f_mode flags to tell ext4
> to use 32-bit or 64-bit hash values for llseek() calls.
> These flags can then used by network file systems, such as NFS, to
> request 32-bit or 64-bit offsets (hashes).
>
> Version 3:
> - remove patch "RFC: Remove check for a 32-bit cookie in nfsd4_readdir()",
>    I think Bruce wanted to take it seperately as bug fix. It should be applied
>    before applying the remaining NFS patches, as without it NFSv4 will always
>    fail with the new 64-bit ext4 seek hashes.
> - split "nfsd: vfs_llseek() with 32 or 64 bit offsets (hashes)" into two
>    two separate patches as suggested by Bruce, one patch to rename
>    'access' to 'may_flags'. And the remainder of the original patch to set
>    FMODE_32BITHASH/FMODE_64BITHASH flags and to introduce the new
>    NFSD_MAY_64BIT_COOKIE flag
>
> Version 2:
> - use f_mode instead of O_* flags and also in a separate patch
> - introduce EXT4_HTREE_EOF_32BIT and EXT4_HTREE_EOF_64BIT
> - fix SEEK_END in ext4_dir_llseek()
> - set f_mode flags in NFS code as early as possible and introduce a new
>    NFSD_MAY_64BIT_COOKIE flag for that
>
> --
> Bernd Schubert
> Fraunhofer ITWM
>
> --
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