[SCSI] sg: completely protect sfds
sfds is protected by sg_index_lock - except for sg_open(), where it
isn't. Change that and add some documentation.
Signed-off-by: Joern Engel <joern@logfs.org>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 8e15c44..53af808 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -146,6 +146,7 @@
} 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 sg_device *parentdp; /* owning device */
wait_queue_head_t read_wait; /* queue read until command done */
@@ -172,6 +173,7 @@
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 */
struct list_head sfds;
volatile char detached; /* 0->attached, 1->detached pending removal */
/* exclude protected by sg_open_exclusive_lock */
@@ -244,6 +246,17 @@
return val;
}
+static int sfds_list_empty(Sg_device *sdp)
+{
+ unsigned long flags;
+ int ret;
+
+ read_lock_irqsave(&sg_index_lock, flags);
+ ret = list_empty(&sdp->sfds);
+ read_unlock_irqrestore(&sg_index_lock, flags);
+ return ret;
+}
+
static int
sg_open(struct inode *inode, struct file *filp)
{
@@ -287,12 +300,12 @@
retval = -EPERM; /* Can't lock it with read only access */
goto error_out;
}
- if (!list_empty(&sdp->sfds) && (flags & O_NONBLOCK)) {
+ if (!sfds_list_empty(sdp) && (flags & O_NONBLOCK)) {
retval = -EBUSY;
goto error_out;
}
res = wait_event_interruptible(sdp->o_excl_wait,
- ((!list_empty(&sdp->sfds) || get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));
+ ((!sfds_list_empty(sdp) || get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));
if (res) {
retval = res; /* -ERESTARTSYS because signal hit process */
goto error_out;
@@ -312,7 +325,7 @@
retval = -ENODEV;
goto error_out;
}
- if (list_empty(&sdp->sfds)) { /* no existing opens on this device */
+ 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);