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51a858817d
When replacing the Big Kernel Lock in commit 2a48fc0ab2 ("block:
autoconvert trivial BKL users to private mutex"), the lock was replaced
with a sr-wide lock.
This causes very poor performance when using multiple sr devices, as the sr
driver was not able to execute more than one command to one drive at any
given time, even when there were many CD drives available.
Replace the global mutex with per-sr-device mutex.
Someone tried this patch at the time, but it never made it upstream, due to
possible concerns with race conditions, but it's not clear the patch
actually caused those:
https://www.spinics.net/lists/linux-scsi/msg63706.html
https://www.spinics.net/lists/linux-scsi/msg63750.html
Also see
http://lists.xiph.org/pipermail/paranoia/2019-December/001647.html
Link: https://lore.kernel.org/r/20200218143918.30267-1-merlijn@archive.org
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Merlijn Wajer <merlijn@archive.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
84 lines
2.7 KiB
C
84 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* sr.h by David Giller
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* CD-ROM disk driver header file
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*
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* adapted from:
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* sd.h Copyright (C) 1992 Drew Eckhardt
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* SCSI disk driver header file by
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* Drew Eckhardt
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*
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* <drew@colorado.edu>
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*
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* Modified by Eric Youngdale eric@andante.org to
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* add scatter-gather, multiple outstanding request, and other
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* enhancements.
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*/
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#ifndef _SR_H
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#define _SR_H
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#include <linux/genhd.h>
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#include <linux/kref.h>
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#include <linux/mutex.h>
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#define MAX_RETRIES 3
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#define SR_TIMEOUT (30 * HZ)
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struct scsi_device;
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/* The CDROM is fairly slow, so we need a little extra time */
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/* In fact, it is very slow if it has to spin up first */
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#define IOCTL_TIMEOUT 30*HZ
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typedef struct scsi_cd {
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struct scsi_driver *driver;
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unsigned capacity; /* size in blocks */
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struct scsi_device *device;
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unsigned int vendor; /* vendor code, see sr_vendor.c */
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unsigned long ms_offset; /* for reading multisession-CD's */
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unsigned writeable : 1;
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unsigned use:1; /* is this device still supportable */
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unsigned xa_flag:1; /* CD has XA sectors ? */
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unsigned readcd_known:1; /* drive supports READ_CD (0xbe) */
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unsigned readcd_cdda:1; /* reading audio data using READ_CD */
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unsigned media_present:1; /* media is present */
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/* GET_EVENT spurious event handling, blk layer guarantees exclusion */
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int tur_mismatch; /* nr of get_event TUR mismatches */
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bool tur_changed:1; /* changed according to TUR */
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bool get_event_changed:1; /* changed according to GET_EVENT */
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bool ignore_get_event:1; /* GET_EVENT is unreliable, use TUR */
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struct cdrom_device_info cdi;
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struct mutex lock;
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/* We hold gendisk and scsi_device references on probe and use
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* the refs on this kref to decide when to release them */
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struct kref kref;
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struct gendisk *disk;
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} Scsi_CD;
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#define sr_printk(prefix, cd, fmt, a...) \
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sdev_prefix_printk(prefix, (cd)->device, (cd)->cdi.name, fmt, ##a)
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int sr_do_ioctl(Scsi_CD *, struct packet_command *);
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int sr_lock_door(struct cdrom_device_info *, int);
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int sr_tray_move(struct cdrom_device_info *, int);
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int sr_drive_status(struct cdrom_device_info *, int);
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int sr_disk_status(struct cdrom_device_info *);
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int sr_get_last_session(struct cdrom_device_info *, struct cdrom_multisession *);
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int sr_get_mcn(struct cdrom_device_info *, struct cdrom_mcn *);
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int sr_reset(struct cdrom_device_info *);
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int sr_select_speed(struct cdrom_device_info *cdi, int speed);
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int sr_audio_ioctl(struct cdrom_device_info *, unsigned int, void *);
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int sr_is_xa(Scsi_CD *);
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/* sr_vendor.c */
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void sr_vendor_init(Scsi_CD *);
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int sr_cd_check(struct cdrom_device_info *);
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int sr_set_blocklength(Scsi_CD *, int blocklength);
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#endif
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