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[Linux] raw IO patches for 2.2, 2.3 (linux IO)


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_ RU.LINUX (2:5077/15.22) ___________________________________________ RU.LINUX _ From : Aleksey I Zavilohin 2:5010/146.29 27 Jul 99 13:20:42 Subj : [Linux] raw IO patches for 2.2, 2.3 ________________________________________________________________________________ Message-ID: <14237.11047.367099.931532@dukat.scot.redhat.com> Date: Tue, 27 Jul 1999 04:44:39 +0100 (BST) To: linux-kernel@vger.rutgers.edu, linux-fsdevel@vger.rutgers.edu Cc: Stephen Tweedie <sct@redhat.com> Subject: New raw IO patches available for 2.2, 2.3 Sender: owner-linux-kernel@vger.rutgers.edu Hi all, /pub/linux/sct/fs/raw-io/raw-19990727.tar.gz contains the latest raw IO code for unbuffered, direct disk IO via standard Unix character mode raw devices. Note that the character major number used in this release has moved from 111 to 162 (that major number should be "official" now). I've included the readme below. This release should work on most 2.2 kernels (2.2.9 upwards at least), and on 2.3.12-pre5. Due to the extensive file locking changes in 2.3 recently, it will not work on older 2.3 kernels. --Stephen ---------------------------------------------------------------- Raw device support v0.5, 27 July 1999 Changed since v0.4: Changed major number from 111 to 162 Added support for 2.3. On 2.3, the internals of the brw_kiovec code now use asynchronous completion from the buffer cache layers. The 2.2 patch here (against 2.2.11-pre1, but it should work on most 2.2 kernels) does not use the new internal asynchronous code, because that would require a change in the VFS buffer_head structure. We don't want to prevent the use of external filesystem modules with raw-enabled kernels. Fixed since v0.3: IOs larger than 64k should work now, thanks to Chris Loveland <cwl@mars.iol.unh.edu> This archive includes patches against both the 2.2.11-pre1 and 2.3.12-pre5 kernels, but you should have luck using the 2.2 version against other 2.2 kernels. The raw devices implemented in this release are genuine Un*x-compatible character-mode raw devices. However, unlike most Unixen, the Linux raw devices are not hard-coded in advance against specific block devices. Rather, there is a new character major number (currently 162) which implements a series of unbound raw devices, and it is up to the system administrator to make sure that these are bound to the appropriate block devices at runtime. This means that _any_ block device can have a character raw device front-end, even if the block device is only loaded later on at runtime. The Makefile in this directory will generate a user front-end program called "raw". It is used as follows: You can query the binding of an existing raw device with raw -l /dev/rawN or raw -a to query them all. To bind a raw device to an existing block device, use either raw /dev/rawN <major> <minor> giving the block-device major and minor numbers directly, or raw /dev/rawN /dev/<blockdev> to bind to an existing device in /dev. Note that the permissions on the raw device are entirely separate from the block device, and you must set the mode and ownership of the raw device appropriately. There are 255 raw devices available for binding, plus a master raw device (with minor number 0) which is used to control the bindings on the others. You can set up a few raw devices to start with via mknod: mknod /dev/raw c 162 0 chmod 600 /dev/raw # This is important! mknod /dev/raw1 c 162 1 mknod /dev/raw2 c 162 2 mknod /dev/raw3 c 162 3 mknod /dev/raw4 c 162 4 and bind them to whatever block devices you want to use: raw /dev/raw1 /dev/sda3 raw /dev/raw2 /dev/fd0 or whatever. Let me know how it works for you! Finally, do remember that these are raw devices. That means: * All IOs must be 512-byte aligned both in memory and on disk * There is no cache coherency between the raw device and the buffered device. --Stehen Tweedie <sct@redhat.com> -- The sun never sets on those who ride into it. -- RKO --- ifmail v.2.14-tx8.9 * Origin: -= home of villain =- (2:5010/146.29@fidonet)

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