From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Matthew Wilcox <willy@debian.org>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>,
Marcelo Tosatti <marcelo@conectiva.com.br>,
Chuck Lever <cel@netapp.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Linux FSdevel <linux-fsdevel@vger.kernel.org>,
NFS maillist <nfs@lists.sourceforge.net>
Subject: Re: [PATCH] 2.4.20 Direct IO patch for NFS. (Note: a trivial API change...)
Date: Mon, 30 Sep 2002 20:57:58 +0200 [thread overview]
Message-ID: <15768.40630.512787.879557@charged.uio.no> (raw)
In-Reply-To: <20020930195235.P18377@parcelfarce.linux.theplanet.co.uk>
>>>>> " " == Matthew Wilcox <willy@debian.org> writes:
>> -static int blkdev_direct_IO(int rw, struct inode * inode,
>> struct kiobuf * iobuf, unsigned long blocknr, int blocksize)
>> +static int blkdev_direct_IO(int rw, struct file * filp, struct
>> kiobuf * iobuf, unsigned long blocknr, int blocksize) {
>> + struct inode * inode =
>> filp->f_dentry->d_inode->i_mapping->host;
>> return generic_direct_IO(rw, inode, iobuf, blocknr, blocksize,
>> blkdev_get_block); }
>>
> isn't that two dereferences more than necessary for a local
> filesystem?
IIRC this is an issue with block filesystems: the i_mapping->host may
differ from d_inode.
It is in any case just the exact same dereference that is being made
in the current version of generic_file_direct_IO(). The API change
simply moves this dereference down into the filesystem code.
Cheers,
Trond
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WARNING: multiple messages have this Message-ID (diff)
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Matthew Wilcox <willy@debian.org>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>,
Marcelo Tosatti <marcelo@conectiva.com.br>,
Chuck Lever <cel@netapp.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Linux FSdevel <linux-fsdevel@vger.kernel.org>,
NFS maillist <nfs@lists.sourceforge.net>
Subject: Re: [PATCH] 2.4.20 Direct IO patch for NFS. (Note: a trivial API change...)
Date: Mon, 30 Sep 2002 20:57:58 +0200 [thread overview]
Message-ID: <15768.40630.512787.879557@charged.uio.no> (raw)
In-Reply-To: <20020930195235.P18377@parcelfarce.linux.theplanet.co.uk>
>>>>> " " == Matthew Wilcox <willy@debian.org> writes:
>> -static int blkdev_direct_IO(int rw, struct inode * inode,
>> struct kiobuf * iobuf, unsigned long blocknr, int blocksize)
>> +static int blkdev_direct_IO(int rw, struct file * filp, struct
>> kiobuf * iobuf, unsigned long blocknr, int blocksize) {
>> + struct inode * inode =
>> filp->f_dentry->d_inode->i_mapping->host;
>> return generic_direct_IO(rw, inode, iobuf, blocknr, blocksize,
>> blkdev_get_block); }
>>
> isn't that two dereferences more than necessary for a local
> filesystem?
IIRC this is an issue with block filesystems: the i_mapping->host may
differ from d_inode.
It is in any case just the exact same dereference that is being made
in the current version of generic_file_direct_IO(). The API change
simply moves this dereference down into the filesystem code.
Cheers,
Trond
next prev parent reply other threads:[~2002-09-30 18:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-30 18:34 [PATCH] 2.4.20 Direct IO patch for NFS. (Note: a trivial API change...) Trond Myklebust
2002-09-30 18:42 ` Christoph Hellwig
2002-09-30 18:46 ` Trond Myklebust
2002-09-30 18:46 ` Trond Myklebust
2002-09-30 19:04 ` Andrew Morton
2002-09-30 19:04 ` Andrew Morton
2002-09-30 19:18 ` Alan Cox
2002-09-30 18:52 ` Matthew Wilcox
2002-09-30 18:57 ` Trond Myklebust [this message]
2002-09-30 18:57 ` Trond Myklebust
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