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https://github.com/torvalds/linux
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9361401eb7
Make it possible to disable the block layer. Not all embedded devices require
it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require
the block layer to be present.
This patch does the following:
(*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev
support.
(*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls
an item that uses the block layer. This includes:
(*) Block I/O tracing.
(*) Disk partition code.
(*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS.
(*) The SCSI layer. As far as I can tell, even SCSI chardevs use the
block layer to do scheduling. Some drivers that use SCSI facilities -
such as USB storage - end up disabled indirectly from this.
(*) Various block-based device drivers, such as IDE and the old CDROM
drivers.
(*) MTD blockdev handling and FTL.
(*) JFFS - which uses set_bdev_super(), something it could avoid doing by
taking a leaf out of JFFS2's book.
(*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and
linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is,
however, still used in places, and so is still available.
(*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and
parts of linux/fs.h.
(*) Makes a number of files in fs/ contingent on CONFIG_BLOCK.
(*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK.
(*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK
is not enabled.
(*) fs/no-block.c is created to hold out-of-line stubs and things that are
required when CONFIG_BLOCK is not set:
(*) Default blockdev file operations (to give error ENODEV on opening).
(*) Makes some /proc changes:
(*) /proc/devices does not list any blockdevs.
(*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK.
(*) Makes some compat ioctl handling contingent on CONFIG_BLOCK.
(*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if
given command other than Q_SYNC or if a special device is specified.
(*) In init/do_mounts.c, no reference is made to the blockdev routines if
CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2.
(*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return
error ENOSYS by way of cond_syscall if so).
(*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if
CONFIG_BLOCK is not set, since they can't then happen.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
149 lines
3.6 KiB
C
149 lines
3.6 KiB
C
#ifndef _SCSI_SCSI_TCQ_H
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#define _SCSI_SCSI_TCQ_H
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#include <linux/blkdev.h>
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#include <scsi/scsi_cmnd.h>
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#include <scsi/scsi_device.h>
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#include <scsi/scsi_host.h>
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#define MSG_SIMPLE_TAG 0x20
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#define MSG_HEAD_TAG 0x21
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#define MSG_ORDERED_TAG 0x22
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#define SCSI_NO_TAG (-1) /* identify no tag in use */
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#ifdef CONFIG_BLOCK
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/**
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* scsi_get_tag_type - get the type of tag the device supports
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* @sdev: the scsi device
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*
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* Notes:
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* If the drive only supports simple tags, returns MSG_SIMPLE_TAG
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* if it supports all tag types, returns MSG_ORDERED_TAG.
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*/
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static inline int scsi_get_tag_type(struct scsi_device *sdev)
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{
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if (!sdev->tagged_supported)
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return 0;
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if (sdev->ordered_tags)
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return MSG_ORDERED_TAG;
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if (sdev->simple_tags)
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return MSG_SIMPLE_TAG;
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return 0;
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}
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static inline void scsi_set_tag_type(struct scsi_device *sdev, int tag)
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{
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switch (tag) {
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case MSG_ORDERED_TAG:
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sdev->ordered_tags = 1;
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/* fall through */
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case MSG_SIMPLE_TAG:
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sdev->simple_tags = 1;
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break;
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case 0:
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/* fall through */
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default:
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sdev->ordered_tags = 0;
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sdev->simple_tags = 0;
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break;
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}
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}
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/**
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* scsi_activate_tcq - turn on tag command queueing
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* @SDpnt: device to turn on TCQ for
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* @depth: queue depth
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*
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* Notes:
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* Eventually, I hope depth would be the maximum depth
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* the device could cope with and the real queue depth
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* would be adjustable from 0 to depth.
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**/
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static inline void scsi_activate_tcq(struct scsi_device *sdev, int depth)
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{
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if (!sdev->tagged_supported)
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return;
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if (!blk_queue_tagged(sdev->request_queue))
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blk_queue_init_tags(sdev->request_queue, depth,
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sdev->host->bqt);
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scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
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}
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/**
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* scsi_deactivate_tcq - turn off tag command queueing
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* @SDpnt: device to turn off TCQ for
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**/
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static inline void scsi_deactivate_tcq(struct scsi_device *sdev, int depth)
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{
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if (blk_queue_tagged(sdev->request_queue))
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blk_queue_free_tags(sdev->request_queue);
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scsi_adjust_queue_depth(sdev, 0, depth);
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}
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/**
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* scsi_populate_tag_msg - place a tag message in a buffer
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* @SCpnt: pointer to the Scsi_Cmnd for the tag
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* @msg: pointer to the area to place the tag
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*
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* Notes:
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* designed to create the correct type of tag message for the
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* particular request. Returns the size of the tag message.
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* May return 0 if TCQ is disabled for this device.
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**/
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static inline int scsi_populate_tag_msg(struct scsi_cmnd *cmd, char *msg)
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{
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struct request *req = cmd->request;
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struct scsi_device *sdev = cmd->device;
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if (blk_rq_tagged(req)) {
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if (sdev->ordered_tags && req->cmd_flags & REQ_HARDBARRIER)
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*msg++ = MSG_ORDERED_TAG;
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else
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*msg++ = MSG_SIMPLE_TAG;
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*msg++ = req->tag;
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return 2;
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}
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return 0;
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}
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/**
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* scsi_find_tag - find a tagged command by device
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* @SDpnt: pointer to the ScSI device
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* @tag: the tag number
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*
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* Notes:
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* Only works with tags allocated by the generic blk layer.
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**/
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static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag)
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{
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struct request *req;
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if (tag != SCSI_NO_TAG) {
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req = blk_queue_find_tag(sdev->request_queue, tag);
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return req ? (struct scsi_cmnd *)req->special : NULL;
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}
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/* single command, look in space */
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return sdev->current_cmnd;
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}
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/**
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* scsi_init_shared_tag_map - create a shared tag map
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* @shost: the host to share the tag map among all devices
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* @depth: the total depth of the map
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*/
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static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
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{
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shost->bqt = blk_init_tags(depth);
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return shost->bqt ? 0 : -ENOMEM;
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}
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#endif /* CONFIG_BLOCK */
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#endif /* _SCSI_SCSI_TCQ_H */
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