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[SCSI] sg: push file descriptor list locking down to per-device locking
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Push file descriptor list locking down to per-device locking. Let sg_index_lock
only protect device lookup.
sdp->detached is also set and checked with this lock held.

Signed-off-by: Vaughan Cao <[email protected]>
Acked-by: Douglas Gilbert <[email protected]>
Signed-off-by: James Bottomley <[email protected]>
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Vaughan Cao authored and James Bottomley committed Sep 3, 2013
1 parent e32c9e6 commit 1f962eb
Showing 1 changed file with 34 additions and 28 deletions.
62 changes: 34 additions & 28 deletions drivers/scsi/sg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -106,8 +106,7 @@ static int sg_add(struct device *, struct class_interface *);
static void sg_remove(struct device *, struct class_interface *);

static DEFINE_IDR(sg_index_idr);
static DEFINE_RWLOCK(sg_index_lock); /* Also used to lock
file descriptor list for device */
static DEFINE_RWLOCK(sg_index_lock);

static struct class_interface sg_interface = {
.add_dev = sg_add,
Expand Down Expand Up @@ -144,8 +143,7 @@ typedef struct sg_request { /* SG_MAX_QUEUE requests outstanding per file */
} Sg_request;

typedef struct sg_fd { /* holds the state of a file descriptor */
/* sfd_siblings is protected by sg_index_lock */
struct list_head sfd_siblings;
struct list_head sfd_siblings; /* protected by sfd_lock of device */
struct sg_device *parentdp; /* owning device */
wait_queue_head_t read_wait; /* queue read until command done */
rwlock_t rq_list_lock; /* protect access to list in req_arr */
Expand All @@ -170,7 +168,7 @@ typedef struct sg_device { /* holds the state of each scsi generic device */
struct scsi_device *device;
int sg_tablesize; /* adapter's max scatter-gather table size */
u32 index; /* device index number */
/* sfds is protected by sg_index_lock */
spinlock_t sfd_lock; /* protect file descriptor list for device */
struct list_head sfds;
struct rw_semaphore o_sem; /* exclude open should hold this rwsem */
volatile char detached; /* 0->attached, 1->detached pending removal */
Expand Down Expand Up @@ -227,9 +225,9 @@ static int sfds_list_empty(Sg_device *sdp)
unsigned long flags;
int ret;

read_lock_irqsave(&sg_index_lock, flags);
spin_lock_irqsave(&sdp->sfd_lock, flags);
ret = list_empty(&sdp->sfds);
read_unlock_irqrestore(&sg_index_lock, flags);
spin_unlock_irqrestore(&sdp->sfd_lock, flags);
return ret;
}

Expand Down Expand Up @@ -1393,6 +1391,7 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
disk->first_minor = k;
sdp->disk = disk;
sdp->device = scsidp;
spin_lock_init(&sdp->sfd_lock);
INIT_LIST_HEAD(&sdp->sfds);
init_rwsem(&sdp->o_sem);
sdp->sg_tablesize = queue_max_segments(q);
Expand Down Expand Up @@ -1527,11 +1526,13 @@ static void sg_remove(struct device *cl_dev, struct class_interface *cl_intf)

/* Need a write lock to set sdp->detached. */
write_lock_irqsave(&sg_index_lock, iflags);
spin_lock(&sdp->sfd_lock);
sdp->detached = 1;
list_for_each_entry(sfp, &sdp->sfds, sfd_siblings) {
wake_up_interruptible(&sfp->read_wait);
kill_fasync(&sfp->async_qp, SIGPOLL, POLL_HUP);
}
spin_unlock(&sdp->sfd_lock);
write_unlock_irqrestore(&sg_index_lock, iflags);

sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");
Expand Down Expand Up @@ -2056,13 +2057,13 @@ sg_add_sfp(Sg_device * sdp, int dev)
sfp->cmd_q = SG_DEF_COMMAND_Q;
sfp->keep_orphan = SG_DEF_KEEP_ORPHAN;
sfp->parentdp = sdp;
write_lock_irqsave(&sg_index_lock, iflags);
spin_lock_irqsave(&sdp->sfd_lock, iflags);
if (sdp->detached) {
write_unlock_irqrestore(&sg_index_lock, iflags);
spin_unlock_irqrestore(&sdp->sfd_lock, iflags);
return ERR_PTR(-ENODEV);
}
list_add_tail(&sfp->sfd_siblings, &sdp->sfds);
write_unlock_irqrestore(&sg_index_lock, iflags);
spin_unlock_irqrestore(&sdp->sfd_lock, iflags);
SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));
if (unlikely(sg_big_buff != def_reserved_size))
sg_big_buff = def_reserved_size;
Expand Down Expand Up @@ -2109,11 +2110,12 @@ static void sg_remove_sfp_usercontext(struct work_struct *work)
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;
unsigned long iflags;

write_lock_irqsave(&sg_index_lock, iflags);
spin_lock_irqsave(&sdp->sfd_lock, iflags);
list_del(&sfp->sfd_siblings);
write_unlock_irqrestore(&sg_index_lock, iflags);
spin_unlock_irqrestore(&sdp->sfd_lock, iflags);

INIT_WORK(&sfp->ew.work, sg_remove_sfp_usercontext);
schedule_work(&sfp->ew.work);
Expand Down Expand Up @@ -2500,7 +2502,7 @@ static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v)
return 0;
}

/* must be called while holding sg_index_lock */
/* must be called while holding sg_index_lock and sfd_lock */
static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
{
int k, m, new_interface, blen, usg;
Expand Down Expand Up @@ -2585,22 +2587,26 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v)

read_lock_irqsave(&sg_index_lock, iflags);
sdp = it ? sg_lookup_dev(it->index) : NULL;
if (sdp && !list_empty(&sdp->sfds)) {
struct scsi_device *scsidp = sdp->device;
if (sdp) {
spin_lock(&sdp->sfd_lock);
if (!list_empty(&sdp->sfds)) {
struct scsi_device *scsidp = sdp->device;

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);
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);
}
spin_unlock(&sdp->sfd_lock);
}
read_unlock_irqrestore(&sg_index_lock, iflags);
return 0;
Expand Down

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