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[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>
This commit is contained in:
Jörn Engel 2012-04-25 11:17:29 -04:00 committed by James Bottomley
parent b499e5249e
commit 035d12e658
1 changed files with 16 additions and 3 deletions
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19
drivers/scsi/sg.c
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@ -146,6 +146,7 @@ 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 sg_device *parentdp; /* owning device */
wait_queue_head_t read_wait; /* queue read until command done */
@ -172,6 +173,7 @@ typedef struct sg_device { /* holds the state of each scsi generic 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 */
struct list_head sfds;
volatile char detached; /* 0->attached, 1->detached pending removal */
/* exclude protected by sg_open_exclusive_lock */
@ -244,6 +246,17 @@ static int set_exclude(Sg_device *sdp, char val)
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 @@ sg_open(struct inode *inode, struct file *filp)
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 @@ sg_open(struct inode *inode, struct file *filp)
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);