[SCSI] sg: fix races during device removal

sg has the following problems related to device removal:

* opening a sg fd races with removing a device
* closing a sg fd races with removing a device
* /proc/scsi/sg/* access races with removing a device
* command completion races with removing a device
* command completion races with closing a sg fd
* can rmmod sg with active commands

These problems can cause kernel oopses, memory-use-after-free, or
double-free errors.  This patch fixes these problems by using krefs
to manage the lifetime of sg_device and sg_fd.

Each command submitted to the midlevel holds a reference to sg_fd
until the completion callback.  This ensures that sg_fd doesn't go
away if the fd is closed with commands still outstanding.

sg_fd gets the reference of sg_device (with scsi_device) and also
makes sure that the sg module doesn't go away.

/proc/scsi/sg/* functions don't play nicely with krefs because they
give information about sg_fds which have been closed but not yet
freed due to still having outstanding commands and sg_devices which
have been removed but not yet freed due to still being referenced
by one or more sg_fds.  To deal with this safely without removing
functionality, /proc functions now access sg_device and sg_fd while
holding a lock instead of using kref_get()/kref_put().

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 201 insertions, 217 deletions

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 516925d8b570..b447527555a7 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -101,6 +101,7 @@ static int scatter_elem_sz_prev = SG_SCATTER_SZ;
 #define SG_SECTOR_MSK (SG_SECTOR_SZ - 1)
 
 static int sg_add(struct device *, struct class_interface *);
+static void sg_device_destroy(struct kref *kref);
 static void sg_remove(struct device *, struct class_interface *);
 
 static DEFINE_IDR(sg_index_idr);
@@ -158,6 +159,8 @@ typedef struct sg_fd {		/* holds the state of a file descriptor */
         char next_cmd_len;      /* 0 -> automatic (def), >0 -> use on next write() */
         char keep_orphan;       /* 0 -> drop orphan (def), 1 -> keep for read() */
         char mmap_called;       /* 0 -> mmap() never called on this fd */
+        struct kref f_ref;
+        struct execute_work ew;
 } Sg_fd;
 
 typedef struct sg_device { /* holds the state of each scsi generic device */
@@ -171,6 +174,7 @@ typedef struct sg_device { /* holds the state of each scsi generic device */
         char sgdebug;           /* 0->off, 1->sense, 9->dump dev, 10-> all devs */
         struct gendisk *disk;
         struct cdev * cdev;     /* char_dev [sysfs: /sys/cdev/major/sg<n>] */
+        struct kref d_ref;
 } Sg_device;
 
 static int sg_fasync(int fd, struct file *filp, int mode);
@@ -194,13 +198,14 @@ static void sg_build_reserve(Sg_fd * sfp, int req_size);
 static void sg_link_reserve(Sg_fd * sfp, Sg_request * srp, int size);
 static void sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp);
 static Sg_fd *sg_add_sfp(Sg_device * sdp, int dev);
-static int sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp);
-static void __sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp);
+static void sg_remove_sfp(struct kref *);
 static Sg_request *sg_get_rq_mark(Sg_fd * sfp, int pack_id);
 static Sg_request *sg_add_request(Sg_fd * sfp);
 static int sg_remove_request(Sg_fd * sfp, Sg_request * srp);
 static int sg_res_in_use(Sg_fd * sfp);
+static Sg_device *sg_lookup_dev(int dev);
 static Sg_device *sg_get_dev(int dev);
+static void sg_put_dev(Sg_device *sdp);
 #ifdef CONFIG_SCSI_PROC_FS
 static int sg_last_dev(void);
 #endif
@@ -237,22 +242,17 @@ sg_open(struct inode *inode, struct file *filp)
         nonseekable_open(inode, filp);
         SCSI_LOG_TIMEOUT(3, printk("sg_open: dev=%d, flags=0x%x\n", dev, flags));
         sdp = sg_get_dev(dev);
-        if ((!sdp) || (!sdp->device)) {
-                unlock_kernel();
-                return -ENXIO;
-        }
-        if (sdp->detached) {
-                unlock_kernel();
-                return -ENODEV;
+        if (IS_ERR(sdp)) {
+                retval = PTR_ERR(sdp);
+                sdp = NULL;
+                goto sg_put;
         }
 
         /* This driver's module count bumped by fops_get in <linux/fs.h> */
         /* Prevent the device driver from vanishing while we sleep */
         retval = scsi_device_get(sdp->device);
-        if (retval) {
-                unlock_kernel();
-                return retval;
-        }
+        if (retval)
+                goto sg_put;
 
         if (!((flags & O_NONBLOCK) ||
               scsi_block_when_processing_errors(sdp->device))) {
@@ -303,16 +303,20 @@ sg_open(struct inode *inode, struct file *filp)
         if ((sfp = sg_add_sfp(sdp, dev)))
                 filp->private_data = sfp;
         else {
-                if (flags & O_EXCL)
+                if (flags & O_EXCL) {
                         sdp->exclude = 0;       /* undo if error */
+                        wake_up_interruptible(&sdp->o_excl_wait);
+                }
                 retval = -ENOMEM;
                 goto error_out;
         }
-        unlock_kernel();
-        return 0;
-
-      error_out:
-        scsi_device_put(sdp->device);
+        retval = 0;
+error_out:
+        if (retval)
+                scsi_device_put(sdp->device);
+sg_put:
+        if (sdp)
+                sg_put_dev(sdp);
         unlock_kernel();
         return retval;
 }
@@ -327,13 +331,13 @@ sg_release(struct inode *inode, struct file *filp)
         if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
                 return -ENXIO;
         SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));
-        if (0 == sg_remove_sfp(sdp, sfp)) {     /* Returns 1 when sdp gone */
-                if (!sdp->detached) {
-                        scsi_device_put(sdp->device);
-                }
-                sdp->exclude = 0;
-                wake_up_interruptible(&sdp->o_excl_wait);
-        }
+
+        sfp->closed = 1;
+
+        sdp->exclude = 0;
+        wake_up_interruptible(&sdp->o_excl_wait);
+
+        kref_put(&sfp->f_ref, sg_remove_sfp);
         return 0;
 }
 
@@ -755,6 +759,7 @@ sg_common_write(Sg_fd * sfp, Sg_request * srp,
         hp->duration = jiffies_to_msecs(jiffies);
 
         srp->rq->timeout = timeout;
+        kref_get(&sfp->f_ref); /* sg_rq_end_io() does kref_put(). */
         blk_execute_rq_nowait(sdp->device->request_queue, sdp->disk,
                               srp->rq, 1, sg_rq_end_io);
         return 0;
@@ -1247,24 +1252,23 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
 static void sg_rq_end_io(struct request *rq, int uptodate)
 {
         struct sg_request *srp = rq->end_io_data;
-        Sg_device *sdp = NULL;
+        Sg_device *sdp;
         Sg_fd *sfp;
         unsigned long iflags;
         unsigned int ms;
         char *sense;
-        int result, resid;
+        int result, resid, done = 1;
 
-        if (NULL == srp) {
-                printk(KERN_ERR "sg_cmd_done: NULL request\n");
+        if (WARN_ON(srp->done != 0))
                 return;
-        }
+
         sfp = srp->parentfp;
-        if (sfp)
-                sdp = sfp->parentdp;
-        if ((NULL == sdp) || sdp->detached) {
-                printk(KERN_INFO "sg_cmd_done: device detached\n");
+        if (WARN_ON(sfp == NULL))
                 return;
-        }
+
+        sdp = sfp->parentdp;
+        if (unlikely(sdp->detached))
+                printk(KERN_INFO "sg_rq_end_io: device detached\n");
 
         sense = rq->sense;
         result = rq->errors;
@@ -1303,33 +1307,26 @@ static void sg_rq_end_io(struct request *rq, int uptodate)
         }
         /* Rely on write phase to clean out srp status values, so no "else" */
 
-        if (sfp->closed) {      /* whoops this fd already released, cleanup */
-                SCSI_LOG_TIMEOUT(1, printk("sg_cmd_done: already closed, freeing ...\n"));
-                sg_finish_rem_req(srp);
-                srp = NULL;
-                if (NULL == sfp->headrp) {
-                        SCSI_LOG_TIMEOUT(1, printk("sg_cmd_done: already closed, final cleanup\n"));
-                        if (0 == sg_remove_sfp(sdp, sfp)) {     /* device still present */
-                                scsi_device_put(sdp->device);
-                        }
-                        sfp = NULL;
-                }
-        } else if (srp && srp->orphan) {
+        write_lock_irqsave(&sfp->rq_list_lock, iflags);
+        if (unlikely(srp->orphan)) {
                 if (sfp->keep_orphan)
                         srp->sg_io_owned = 0;
-                else {
-                        sg_finish_rem_req(srp);
-                        srp = NULL;
-                }
+                else
+                        done = 0;
         }
-        if (sfp && srp) {
-                /* Now wake up any sg_read() that is waiting for this packet. */
-                kill_fasync(&sfp->async_qp, SIGPOLL, POLL_IN);
-                write_lock_irqsave(&sfp->rq_list_lock, iflags);
-                srp->done = 1;
+        srp->done = done;
+        write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+
+        if (likely(done)) {
+                /* Now wake up any sg_read() that is waiting for this
+                 * packet.
+                 */
                 wake_up_interruptible(&sfp->read_wait);
-                write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
-        }
+                kill_fasync(&sfp->async_qp, SIGPOLL, POLL_IN);
+        } else
+                sg_finish_rem_req(srp); /* call with srp->done == 0 */
+
+        kref_put(&sfp->f_ref, sg_remove_sfp);
 }
 
 static struct file_operations sg_fops = {
@@ -1364,17 +1361,18 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
                 printk(KERN_WARNING "kmalloc Sg_device failure\n");
                 return ERR_PTR(-ENOMEM);
         }
-        error = -ENOMEM;
+
         if (!idr_pre_get(&sg_index_idr, GFP_KERNEL)) {
                 printk(KERN_WARNING "idr expansion Sg_device failure\n");
+                error = -ENOMEM;
                 goto out;
         }
 
         write_lock_irqsave(&sg_index_lock, iflags);
-        error = idr_get_new(&sg_index_idr, sdp, &k);
-        write_unlock_irqrestore(&sg_index_lock, iflags);
 
+        error = idr_get_new(&sg_index_idr, sdp, &k);
         if (error) {
+                write_unlock_irqrestore(&sg_index_lock, iflags);
                 printk(KERN_WARNING "idr allocation Sg_device failure: %d\n",
                        error);
                 goto out;
@@ -1391,6 +1389,9 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
         init_waitqueue_head(&sdp->o_excl_wait);
         sdp->sg_tablesize = min(q->max_hw_segments, q->max_phys_segments);
         sdp->index = k;
+        kref_init(&sdp->d_ref);
+
+        write_unlock_irqrestore(&sg_index_lock, iflags);
 
         error = 0;
  out:
@@ -1401,6 +1402,8 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
         return sdp;
 
  overflow:
+        idr_remove(&sg_index_idr, k);
+        write_unlock_irqrestore(&sg_index_lock, iflags);
         sdev_printk(KERN_WARNING, scsidp,
                     "Unable to attach sg device type=%d, minor "
                     "number exceeds %d\n", scsidp->type, SG_MAX_DEVS - 1);
@@ -1488,49 +1491,46 @@ out:
         return error;
 }
 
-static void
-sg_remove(struct device *cl_dev, struct class_interface *cl_intf)
+static void sg_device_destroy(struct kref *kref)
+{
+        struct sg_device *sdp = container_of(kref, struct sg_device, d_ref);
+        unsigned long flags;
+
+        /* CAUTION!  Note that the device can still be found via idr_find()
+         * even though the refcount is 0.  Therefore, do idr_remove() BEFORE
+         * any other cleanup.
+         */
+
+        write_lock_irqsave(&sg_index_lock, flags);
+        idr_remove(&sg_index_idr, sdp->index);
+        write_unlock_irqrestore(&sg_index_lock, flags);
+
+        SCSI_LOG_TIMEOUT(3,
+                printk("sg_device_destroy: %s\n",
+                        sdp->disk->disk_name));
+
+        put_disk(sdp->disk);
+        kfree(sdp);
+}
+
+static void sg_remove(struct device *cl_dev, struct class_interface *cl_intf)
 {
         struct scsi_device *scsidp = to_scsi_device(cl_dev->parent);
         Sg_device *sdp = dev_get_drvdata(cl_dev);
         unsigned long iflags;
         Sg_fd *sfp;
-        Sg_fd *tsfp;
-        Sg_request *srp;
-        Sg_request *tsrp;
-        int delay;
 
-        if (!sdp)
+        if (!sdp || sdp->detached)
                 return;
 
-        delay = 0;
+        SCSI_LOG_TIMEOUT(3, printk("sg_remove: %s\n", sdp->disk->disk_name));
+
+        /* Need a write lock to set sdp->detached. */
         write_lock_irqsave(&sg_index_lock, iflags);
-        if (sdp->headfp) {
-                sdp->detached = 1;
-                for (sfp = sdp->headfp; sfp; sfp = tsfp) {
-                        tsfp = sfp->nextfp;
-                        for (srp = sfp->headrp; srp; srp = tsrp) {
-                                tsrp = srp->nextrp;
-                                if (sfp->closed || (0 == sg_srp_done(srp, sfp)))
-                                        sg_finish_rem_req(srp);
-                        }
-                        if (sfp->closed) {
-                                scsi_device_put(sdp->device);
-                                __sg_remove_sfp(sdp, sfp);
-                        } else {
-                                delay = 1;
-                                wake_up_interruptible(&sfp->read_wait);
-                                kill_fasync(&sfp->async_qp, SIGPOLL,
-                                            POLL_HUP);
-                        }
-                }
-                SCSI_LOG_TIMEOUT(3, printk("sg_remove: dev=%d, dirty\n", sdp->index));
-                if (NULL == sdp->headfp) {
-                        idr_remove(&sg_index_idr, sdp->index);
-                }
-        } else {        /* nothing active, simple case */
-                SCSI_LOG_TIMEOUT(3, printk("sg_remove: dev=%d\n", sdp->index));
-                idr_remove(&sg_index_idr, sdp->index);
+        sdp->detached = 1;
+        for (sfp = sdp->headfp; sfp; sfp = sfp->nextfp) {
+                wake_up_interruptible(&sfp->read_wait);
+                kill_fasync(&sfp->async_qp, SIGPOLL, POLL_HUP);
         }
         write_unlock_irqrestore(&sg_index_lock, iflags);
 
@@ -1538,13 +1538,8 @@ sg_remove(struct device *cl_dev, struct class_interface *cl_intf)
         device_destroy(sg_sysfs_class, MKDEV(SCSI_GENERIC_MAJOR, sdp->index));
         cdev_del(sdp->cdev);
         sdp->cdev = NULL;
-        put_disk(sdp->disk);
-        sdp->disk = NULL;
-        if (NULL == sdp->headfp)
-                kfree(sdp);
 
-        if (delay)
-                msleep(10);     /* dirty detach so delay device destruction */
+        sg_put_dev(sdp);
 }
 
 module_param_named(scatter_elem_sz, scatter_elem_sz, int, S_IRUGO | S_IWUSR);
@@ -1941,22 +1936,6 @@ sg_get_rq_mark(Sg_fd * sfp, int pack_id)
         return resp;
 }
 
-#ifdef CONFIG_SCSI_PROC_FS
-static Sg_request *
-sg_get_nth_request(Sg_fd * sfp, int nth)
-{
-        Sg_request *resp;
-        unsigned long iflags;
-        int k;
-
-        read_lock_irqsave(&sfp->rq_list_lock, iflags);
-        for (k = 0, resp = sfp->headrp; resp && (k < nth);
-             ++k, resp = resp->nextrp) ;
-        read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
-        return resp;
-}
-#endif
-
 /* always adds to end of list */
 static Sg_request *
 sg_add_request(Sg_fd * sfp)
@@ -2032,22 +2011,6 @@ sg_remove_request(Sg_fd * sfp, Sg_request * srp)
         return res;
 }
 
-#ifdef CONFIG_SCSI_PROC_FS
-static Sg_fd *
-sg_get_nth_sfp(Sg_device * sdp, int nth)
-{
-        Sg_fd *resp;
-        unsigned long iflags;
-        int k;
-
-        read_lock_irqsave(&sg_index_lock, iflags);
-        for (k = 0, resp = sdp->headfp; resp && (k < nth);
-             ++k, resp = resp->nextfp) ;
-        read_unlock_irqrestore(&sg_index_lock, iflags);
-        return resp;
-}
-#endif
-
 static Sg_fd *
 sg_add_sfp(Sg_device * sdp, int dev)
 {
@@ -2062,6 +2025,7 @@ sg_add_sfp(Sg_device * sdp, int dev)
         init_waitqueue_head(&sfp->read_wait);
         rwlock_init(&sfp->rq_list_lock);
 
+        kref_init(&sfp->f_ref);
         sfp->timeout = SG_DEFAULT_TIMEOUT;
         sfp->timeout_user = SG_DEFAULT_TIMEOUT_USER;
         sfp->force_packid = SG_DEF_FORCE_PACK_ID;
@@ -2089,15 +2053,54 @@ sg_add_sfp(Sg_device * sdp, int dev)
         sg_build_reserve(sfp, bufflen);
         SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp:   bufflen=%d, k_use_sg=%d\n",
                            sfp->reserve.bufflen, sfp->reserve.k_use_sg));
+
+        kref_get(&sdp->d_ref);
+        __module_get(THIS_MODULE);
         return sfp;
 }
 
-static void
-__sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp)
+static void sg_remove_sfp_usercontext(struct work_struct *work)
+{
+        struct sg_fd *sfp = container_of(work, struct sg_fd, ew.work);
+        struct sg_device *sdp = sfp->parentdp;
+
+        /* Cleanup any responses which were never read(). */
+        while (sfp->headrp)
+                sg_finish_rem_req(sfp->headrp);
+
+        if (sfp->reserve.bufflen > 0) {
+                SCSI_LOG_TIMEOUT(6,
+                        printk("sg_remove_sfp:    bufflen=%d, k_use_sg=%d\n",
+                                (int) sfp->reserve.bufflen,
+                                (int) sfp->reserve.k_use_sg));
+                sg_remove_scat(&sfp->reserve);
+        }
+
+        SCSI_LOG_TIMEOUT(6,
+                printk("sg_remove_sfp: %s, sfp=0x%p\n",
+                        sdp->disk->disk_name,
+                        sfp));
+        kfree(sfp);
+
+        scsi_device_put(sdp->device);
+        sg_put_dev(sdp);
+        module_put(THIS_MODULE);
+}
+
+static void sg_remove_sfp(struct kref *kref)
 {
+        struct sg_fd *sfp = container_of(kref, struct sg_fd, f_ref);
+        struct sg_device *sdp = sfp->parentdp;
         Sg_fd *fp;
         Sg_fd *prev_fp;
+        unsigned long iflags;
+
+        /* CAUTION!  Note that sfp can still be found by walking sdp->headfp
+         * even though the refcount is now 0.  Therefore, unlink sfp from
+         * sdp->headfp BEFORE doing any other cleanup.
+         */
 
+        write_lock_irqsave(&sg_index_lock, iflags);
         prev_fp = sdp->headfp;
         if (sfp == prev_fp)
                 sdp->headfp = prev_fp->nextfp;
@@ -2110,54 +2113,10 @@ __sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp)
                         prev_fp = fp;
                 }
         }
-        if (sfp->reserve.bufflen > 0) {
-                SCSI_LOG_TIMEOUT(6, 
-                        printk("__sg_remove_sfp:    bufflen=%d, k_use_sg=%d\n",
-                        (int) sfp->reserve.bufflen, (int) sfp->reserve.k_use_sg));
-                sg_remove_scat(&sfp->reserve);
-        }
-        sfp->parentdp = NULL;
-        SCSI_LOG_TIMEOUT(6, printk("__sg_remove_sfp:    sfp=0x%p\n", sfp));
-        kfree(sfp);
-}
-
-/* Returns 0 in normal case, 1 when detached and sdp object removed */
-static int
-sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp)
-{
-        Sg_request *srp;
-        Sg_request *tsrp;
-        int dirty = 0;
-        int res = 0;
-
-        for (srp = sfp->headrp; srp; srp = tsrp) {
-                tsrp = srp->nextrp;
-                if (sg_srp_done(srp, sfp))
-                        sg_finish_rem_req(srp);
-                else
-                        ++dirty;
-        }
-        if (0 == dirty) {
-                unsigned long iflags;
+        write_unlock_irqrestore(&sg_index_lock, iflags);
+        wake_up_interruptible(&sdp->o_excl_wait);
 
-                write_lock_irqsave(&sg_index_lock, iflags);
-                __sg_remove_sfp(sdp, sfp);
-                if (sdp->detached && (NULL == sdp->headfp)) {
-                        idr_remove(&sg_index_idr, sdp->index);
-                        kfree(sdp);
-                        res = 1;
-                }
-                write_unlock_irqrestore(&sg_index_lock, iflags);
-        } else {
-                /* MOD_INC's to inhibit unloading sg and associated adapter driver */
-                /* only bump the access_count if we actually succeeded in
-                 * throwing another counter on the host module */
-                scsi_device_get(sdp->device);   /* XXX: retval ignored? */      
-                sfp->closed = 1;        /* flag dirty state on this fd */
-                SCSI_LOG_TIMEOUT(1, printk("sg_remove_sfp: worrisome, %d writes pending\n",
-                                  dirty));
-        }
-        return res;
+        execute_in_process_context(sg_remove_sfp_usercontext, &sfp->ew);
 }
 
 static int
@@ -2199,19 +2158,38 @@ sg_last_dev(void)
 }
 #endif
 
-static Sg_device *
-sg_get_dev(int dev)
+/* must be called with sg_index_lock held */
+static Sg_device *sg_lookup_dev(int dev)
 {
-        Sg_device *sdp;
-        unsigned long iflags;
+        return idr_find(&sg_index_idr, dev);
+}
 
-        read_lock_irqsave(&sg_index_lock, iflags);
-        sdp = idr_find(&sg_index_idr, dev);
-        read_unlock_irqrestore(&sg_index_lock, iflags);
+static Sg_device *sg_get_dev(int dev)
+{
+        struct sg_device *sdp;
+        unsigned long flags;
+
+        read_lock_irqsave(&sg_index_lock, flags);
+        sdp = sg_lookup_dev(dev);
+        if (!sdp)
+                sdp = ERR_PTR(-ENXIO);
+        else if (sdp->detached) {
+                /* If sdp->detached, then the refcount may already be 0, in
+                 * which case it would be a bug to do kref_get().
+                 */
+                sdp = ERR_PTR(-ENODEV);
+        } else
+                kref_get(&sdp->d_ref);
+        read_unlock_irqrestore(&sg_index_lock, flags);
 
         return sdp;
 }
 
+static void sg_put_dev(struct sg_device *sdp)
+{
+        kref_put(&sdp->d_ref, sg_device_destroy);
+}
+
 #ifdef CONFIG_SCSI_PROC_FS
 
 static struct proc_dir_entry *sg_proc_sgp = NULL;
@@ -2468,8 +2446,10 @@ static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
         struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
         Sg_device *sdp;
         struct scsi_device *scsidp;
+        unsigned long iflags;
 
-        sdp = it ? sg_get_dev(it->index) : NULL;
+        read_lock_irqsave(&sg_index_lock, iflags);
+        sdp = it ? sg_lookup_dev(it->index) : NULL;
         if (sdp && (scsidp = sdp->device) && (!sdp->detached))
                 seq_printf(s, "%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\n",
                               scsidp->host->host_no, scsidp->channel,
@@ -2480,6 +2460,7 @@ static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
                               (int) scsi_device_online(scsidp));
         else
                 seq_printf(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n");
+        read_unlock_irqrestore(&sg_index_lock, iflags);
         return 0;
 }
 
@@ -2493,16 +2474,20 @@ static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v)
         struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
         Sg_device *sdp;
         struct scsi_device *scsidp;
+        unsigned long iflags;
 
-        sdp = it ? sg_get_dev(it->index) : NULL;
+        read_lock_irqsave(&sg_index_lock, iflags);
+        sdp = it ? sg_lookup_dev(it->index) : NULL;
         if (sdp && (scsidp = sdp->device) && (!sdp->detached))
                 seq_printf(s, "%8.8s\t%16.16s\t%4.4s\n",
                            scsidp->vendor, scsidp->model, scsidp->rev);
         else
                 seq_printf(s, "<no active device>\n");
+        read_unlock_irqrestore(&sg_index_lock, iflags);
         return 0;
 }
 
+/* must be called while holding sg_index_lock */
 static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
 {
         int k, m, new_interface, blen, usg;
@@ -2512,7 +2497,8 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
         const char * cp;
         unsigned int ms;
 
-        for (k = 0; (fp = sg_get_nth_sfp(sdp, k)); ++k) {
+        for (k = 0, fp = sdp->headfp; fp != NULL; ++k, fp = fp->nextfp) {
+                read_lock(&fp->rq_list_lock); /* irqs already disabled */
                 seq_printf(s, "   FD(%d): timeout=%dms bufflen=%d "
                            "(res)sgat=%d low_dma=%d\n", k + 1,
                            jiffies_to_msecs(fp->timeout),
@@ -2522,7 +2508,9 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
                 seq_printf(s, "   cmd_q=%d f_packid=%d k_orphan=%d closed=%d\n",
                            (int) fp->cmd_q, (int) fp->force_packid,
                            (int) fp->keep_orphan, (int) fp->closed);
-                for (m = 0; (srp = sg_get_nth_request(fp, m)); ++m) {
+                for (m = 0, srp = fp->headrp;
+                                srp != NULL;
+                                ++m, srp = srp->nextrp) {
                         hp = &srp->header;
                         new_interface = (hp->interface_id == '\0') ? 0 : 1;
                         if (srp->res_used) {
@@ -2559,6 +2547,7 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
                 }
                 if (0 == m)
                         seq_printf(s, "     No requests active\n");
+                read_unlock(&fp->rq_list_lock);
         }
 }
 
@@ -2571,39 +2560,34 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v)
 {
         struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
         Sg_device *sdp;
+        unsigned long iflags;
 
         if (it && (0 == it->index)) {
                 seq_printf(s, "max_active_device=%d(origin 1)\n",
                            (int)it->max);
                 seq_printf(s, " def_reserved_size=%d\n", sg_big_buff);
         }
-        sdp = it ? sg_get_dev(it->index) : NULL;
-        if (sdp) {
-                struct scsi_device *scsidp = sdp->device;
 
-                if (NULL == scsidp) {
-                        seq_printf(s, "device %d detached ??\n", 
-                                   (int)it->index);
-                        return 0;
-                }
+        read_lock_irqsave(&sg_index_lock, iflags);
+        sdp = it ? sg_lookup_dev(it->index) : NULL;
+        if (sdp && sdp->headfp) {
+                struct scsi_device *scsidp = sdp->device;
 
-                if (sg_get_nth_sfp(sdp, 0)) {
-                        seq_printf(s, " >>> device=%s ",
-                                sdp->disk->disk_name);
-                        if (sdp->detached)
-                                seq_printf(s, "detached pending close ");
-                        else
-                                seq_printf
-                                    (s, "scsi%d chan=%d id=%d lun=%d   em=%d",
-                                     scsidp->host->host_no,
-                                     scsidp->channel, scsidp->id,
-                                     scsidp->lun,
-                                     scsidp->host->hostt->emulated);
-                        seq_printf(s, " sg_tablesize=%d excl=%d\n",
-                                   sdp->sg_tablesize, sdp->exclude);
-                }
+                seq_printf(s, " >>> device=%s ", sdp->disk->disk_name);
+                if (sdp->detached)
+                        seq_printf(s, "detached pending close ");
+                else
+                        seq_printf
+                            (s, "scsi%d chan=%d id=%d lun=%d   em=%d",
+                             scsidp->host->host_no,
+                             scsidp->channel, scsidp->id,
+                             scsidp->lun,
+                             scsidp->host->hostt->emulated);
+                seq_printf(s, " sg_tablesize=%d excl=%d\n",
+                           sdp->sg_tablesize, sdp->exclude);
                 sg_proc_debug_helper(s, sdp);
         }
+        read_unlock_irqrestore(&sg_index_lock, iflags);
         return 0;
 }