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[SCSI] Revert "sg: use rwsem to solve race during exclusive open" 

This reverts commit 15b06f9a02.

This is one of four patches that was causing this bug

[  205.372823] ================================================
[  205.372901] [ BUG: lock held when returning to user space! ]
[  205.372979] 3.12.0-rc6-hw-debug-pagealloc+ #67 Not tainted
[  205.373055] ------------------------------------------------
[  205.373132] megarc.bin/5283 is leaving the kernel with locks still held!
[  205.373212] 1 lock held by megarc.bin/5283:
[  205.373285]  #0:  (&sdp->o_sem){.+.+..}, at: [<ffffffff8161e650>] sg_open+0x3a0/0x4d0

Cc: Vaughan Cao <vaughan.cao@oracle.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
James Bottomley 2013-10-25 10:27:02 +01:00
parent 98481ff0bb
commit 065b4a2f59
1 changed files with 38 additions and 41 deletions
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79
drivers/scsi/sg.c
View File

@ -170,11 +170,11 @@ 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 */
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 */
@ -265,6 +265,7 @@ sg_open(struct inode *inode, struct file *filp)
struct request_queue *q;
Sg_device *sdp;
Sg_fd *sfp;
int res;
int retval;
nonseekable_open(inode, filp);
@ -293,35 +294,35 @@ sg_open(struct inode *inode, struct file *filp)
goto error_out;
}
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;
}
} else {
if (!down_read_trylock(&sdp->o_sem)) {
retval = -EBUSY;
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;
}
} else {
if (flags & O_EXCL)
down_write(&sdp->o_sem);
else
down_read(&sdp->o_sem);
}
/* Since write lock is held, no need to check sfd_list */
if (flags & O_EXCL)
set_exclude(sdp, 1);
if (sdp->detached) {
retval = -ENODEV;
goto sem_out;
goto error_out;
}
if (sfds_list_empty(sdp)) { /* no existing opens on this device */
sdp->sgdebug = 0;
@ -330,18 +331,17 @@ sg_open(struct inode *inode, struct file *filp)
}
if ((sfp = sg_add_sfp(sdp, dev)))
filp->private_data = sfp;
/* retval is already provably zero at this point because of the
* check after retval = scsi_autopm_get_device(sdp->device))
*/
else {
retval = -ENOMEM;
sem_out:
if (flags & O_EXCL) {
set_exclude(sdp, 0); /* undo if error */
up_write(&sdp->o_sem);
} else
up_read(&sdp->o_sem);
wake_up_interruptible(&sdp->o_excl_wait);
}
retval = -ENOMEM;
goto error_out;
}
retval = 0;
error_out:
if (retval) {
scsi_autopm_put_device(sdp->device);
sdp_put:
scsi_device_put(sdp->device);
@ -358,18 +358,13 @@ sg_release(struct inode *inode, struct file *filp)
{
Sg_device *sdp;
Sg_fd *sfp;
int excl;
if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
return -ENXIO;
SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));
excl = get_exclude(sdp);
set_exclude(sdp, 0);
if (excl)
up_write(&sdp->o_sem);
else
up_read(&sdp->o_sem);
wake_up_interruptible(&sdp->o_excl_wait);
scsi_autopm_put_device(sdp->device);
kref_put(&sfp->f_ref, sg_remove_sfp);
@ -1421,7 +1416,7 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
sdp->disk = disk;
sdp->device = scsidp;
INIT_LIST_HEAD(&sdp->sfds);
init_rwsem(&sdp->o_sem);
init_waitqueue_head(&sdp->o_excl_wait);
sdp->sg_tablesize = queue_max_segments(q);
sdp->index = k;
kref_init(&sdp->d_ref);
@ -2132,11 +2127,13 @@ 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);
list_del(&sfp->sfd_siblings);
write_unlock_irqrestore(&sg_index_lock, iflags);
wake_up_interruptible(&sdp->o_excl_wait);
INIT_WORK(&sfp->ew.work, sg_remove_sfp_usercontext);
schedule_work(&sfp->ew.work);