Use rwsem to aid opens. Exclusive open has to get write lock and non-exclusive
open should get read lock.
Replace global sg_open_exclusive_lock with a per device lock - sfd_lock. Since
sfds list is now protected by the lock owned by the same sg_device,
sg_index_lock becomes a real global lock to only protect sg devices lookup.
Please pay attention to sdp->detached. Previously sg_open may also race with
sg_remove. Now there are two points for sg_open to detect detached and finish
itself. One is at sg_device lookup and the other is when trying to link new sfp
into the sfds list in sg_add_sfp.
I don't think it's necessary to do extra set_exclude and wake_up o_excl_wait in
sg_release before, so I remove them and only do the cleanup in sg_remove_sfp.
Although simple testcases are passed, I'm not certain if I've fixed it well,
please give me any comments as you wish.
Signed-off-by: Vaughan Cao <vaughan....@oracle.com>
---
drivers/scsi/sg.c | 187 ++++++++++++++++++++++++++----------------------------
1 file changed, 89 insertions(+), 98 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 25b5455..3fc8c19 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -103,11 +103,8 @@ static int scatter_elem_sz_prev = SG_SCATTER_SZ;
static int sg_add(struct device *, struct class_interface *);
static void sg_remove(struct device *, struct class_interface *);
-static DEFINE_SPINLOCK(sg_open_exclusive_lock);
-
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); /* protect sg index */
static struct class_interface sg_interface = {
.add_dev = sg_add,
@@ -144,7 +141,7 @@ 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 */
+ /* sfd_siblings is protected by sfd_lock of sg_device */
struct list_head sfd_siblings;
struct sg_device *parentdp; /* owning device */
wait_queue_head_t read_wait; /* queue read until command done */
@@ -168,13 +165,12 @@ typedef struct sg_fd { /* holds the state of a
file descriptor */
typedef struct sg_device { /* holds the state of each scsi generic device */
struct scsi_device *device;
- wait_queue_head_t o_excl_wait; /* queue open() when O_EXCL in use */
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 sfds, exclude */
struct list_head sfds;
+ struct rw_semaphore o_sem; /* exclude open should hold this rwsem
*/
volatile char detached; /* 0->attached, 1->detached pending removal */
- /* exclude protected by sg_open_exclusive_lock */
char exclude; /* opened for exclusive access */
char sgdebug; /* 0->off, 1->sense, 9->dump dev, 10-> all devs
*/
struct gendisk *disk;
@@ -199,7 +195,7 @@ static void sg_remove_scat(Sg_scatter_hold * schp);
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 Sg_fd *sg_add_sfp(Sg_device * sdp, int dev, int excl, int * reason);
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);
@@ -224,35 +220,14 @@ static int sg_allow_access(struct file *filp, unsigned
char *cmd)
return blk_verify_command(q, cmd, filp->f_mode & FMODE_WRITE);
}
-static int get_exclude(Sg_device *sdp)
-{
- unsigned long flags;
- int ret;
-
- spin_lock_irqsave(&sg_open_exclusive_lock, flags);
- ret = sdp->exclude;
- spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
- return ret;
-}
-
-static int set_exclude(Sg_device *sdp, char val)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&sg_open_exclusive_lock, flags);
- sdp->exclude = val;
- spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
- return val;
-}
-
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;
}
@@ -264,8 +239,8 @@ sg_open(struct inode *inode, struct file *filp)
struct request_queue *q;
Sg_device *sdp;
Sg_fd *sfp;
- int res;
int retval;
+ unsigned long iflags;
nonseekable_open(inode, filp);
SCSI_LOG_TIMEOUT(3, printk("sg_open: dev=%d, flags=0x%x\n", dev,
flags));
@@ -293,52 +268,45 @@ sg_open(struct inode *inode, struct file *filp)
goto error_out;
}
- if (flags & O_EXCL) {
- if (O_RDONLY == (flags & O_ACCMODE)) {
- retval = -EPERM; /* Can't lock it with read only access
*/
- goto error_out;
- }
- if (!sfds_list_empty(sdp) && (flags & O_NONBLOCK)) {
- retval = -EBUSY;
- goto error_out;
- }
- res = wait_event_interruptible(sdp->o_excl_wait,
- ((!sfds_list_empty(sdp) ||
get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));
- if (res) {
- retval = res; /* -ERESTARTSYS because signal hit
process */
- goto error_out;
- }
- } else if (get_exclude(sdp)) { /* some other fd has an exclusive lock
on dev */
- if (flags & O_NONBLOCK) {
- retval = -EBUSY;
- goto error_out;
- }
- res = wait_event_interruptible(sdp->o_excl_wait,
!get_exclude(sdp));
- if (res) {
- retval = res; /* -ERESTARTSYS because signal hit
process */
- goto error_out;
- }
- }
- if (sdp->detached) {
- retval = -ENODEV;
+ if ((flags & O_EXCL) && (O_RDONLY == (flags & O_ACCMODE))) {
+ retval = -EPERM; /* Can't lock it with read only access */
goto error_out;
}
+ if (flags & O_NONBLOCK) {
+ if (flags & O_EXCL) {
+ if (!down_write_trylock(&sdp->o_sem)) {
+ retval = -EBUSY;
+ goto error_out;
+ }
+ /* if write lock is held, there is only one user. */
+ } else {
+ if (!down_read_trylock(&sdp->o_sem)) {
+ retval = -EBUSY;
+ goto error_out;
+ }
+ }
+ } else {
+ if (flags & O_EXCL)
+ down_write(&sdp->o_sem);
+ else
+ down_read(&sdp->o_sem);
+ }
+
if (sfds_list_empty(sdp)) { /* no existing opens on this device */
sdp->sgdebug = 0;
q = sdp->device->request_queue;
sdp->sg_tablesize = queue_max_segments(q);
}
- if ((sfp = sg_add_sfp(sdp, dev)))
- filp->private_data = sfp;
- else {
- if (flags & O_EXCL) {
- set_exclude(sdp, 0); /* undo if error */
- wake_up_interruptible(&sdp->o_excl_wait);
- }
- retval = -ENOMEM;
- goto error_out;
- }
+ if (!(sfp = sg_add_sfp(sdp, dev, (flags & O_EXCL ? 1 : 0), &retval)))
+ goto sem_out;
+ filp->private_data = sfp;
retval = 0;
+sem_out:
+ if (retval)
+ if (flags & O_EXCL)
+ up_write(&sdp->o_sem);
+ else
+ up_read(&sdp->o_sem);
error_out:
if (retval) {
scsi_autopm_put_device(sdp->device);
@@ -362,9 +330,6 @@ sg_release(struct inode *inode, struct file *filp)
return -ENXIO;
SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));
- set_exclude(sdp, 0);
- wake_up_interruptible(&sdp->o_excl_wait);
-
scsi_autopm_put_device(sdp->device);
kref_put(&sfp->f_ref, sg_remove_sfp);
return 0;
@@ -1414,8 +1379,9 @@ 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_waitqueue_head(&sdp->o_excl_wait);
+ init_rwsem(&sdp->o_sem);
sdp->sg_tablesize = queue_max_segments(q);
sdp->index = k;
kref_init(&sdp->d_ref);
@@ -1556,11 +1522,13 @@ 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");
@@ -2063,15 +2031,18 @@ sg_remove_request(Sg_fd * sfp, Sg_request * srp)
}
static Sg_fd *
-sg_add_sfp(Sg_device * sdp, int dev)
+sg_add_sfp(Sg_device * sdp, int dev, int excl, int * reason)
{
Sg_fd *sfp;
unsigned long iflags;
int bufflen;
sfp = kzalloc(sizeof(*sfp), GFP_ATOMIC | __GFP_NOWARN);
- if (!sfp)
+ if (!sfp) {
+ if (reason)
+ *reason = -ENOMEM;
return NULL;
+ }
init_waitqueue_head(&sfp->read_wait);
rwlock_init(&sfp->rq_list_lock);
@@ -2085,9 +2056,19 @@ 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) {
+ spin_unlock_irqrestore(&sdp->sfd_lock, iflags);
+ if (reason)
+ *reason = -ENODEV;
+ return NULL;
+ }
list_add_tail(&sfp->sfd_siblings, &sdp->sfds);
- write_unlock_irqrestore(&sg_index_lock, iflags);
+ if (excl)
+ sdp->exclude = 1;
+ 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;
@@ -2136,11 +2117,17 @@ 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;
+ int excl;
- 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);
- wake_up_interruptible(&sdp->o_excl_wait);
+ if ((excl = sdp->exclude))
+ sdp->exclude = 0;
+ spin_unlock_irqrestore(&sdp->sfd_lock, iflags);
+ if (excl)
+ up_write(&sdp->o_sem);
+ else
+ up_read(&sdp->o_sem);
INIT_WORK(&sfp->ew.work, sg_remove_sfp_usercontext);
schedule_work(&sfp->ew.work);
@@ -2531,7 +2518,7 @@ 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;
@@ -2616,22 +2603,26 @@ 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, get_exclude(sdp));
- 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;
--
1.7.11.7
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