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Message-Id: <1377741639-3693-5-git-send-email-vaughan.cao@oracle.com>
Date: Thu, 29 Aug 2013 10:00:39 +0800
From: Vaughan Cao <vaughan.cao@...cle.com>
To: James.Bottomley@...senPartnership.com
Cc: joern@...fs.org, vaughan.cao@...cle.com, dgilbert@...erlog.com,
JBottomley@...allels.com, linux-scsi@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v7 4/4] sg: push file descriptor list locking down to per-device locking
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.
Changes from v4:
* Since I use ERR_PTR and friends in sg_add_sfp, this patch should also be
updated to resolve conflict in cherrry-pick.
Signed-off-by: Vaughan Cao <vaughan.cao@...cle.com>
---
drivers/scsi/sg.c | 62 ++++++++++++++++++++++++++++++-------------------------
1 file changed, 34 insertions(+), 28 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 64df1ab..5cbc4bb 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -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,
@@ -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 */
@@ -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 */
@@ -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;
}
@@ -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);
@@ -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");
@@ -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;
@@ -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);
@@ -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;
@@ -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;
--
1.8.3.1
--
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