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[SCSI] Revert "sg: no need sg_open_exclusive_lock"

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This reverts commit 00b2d9d6d0.

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 10:26:38 +01:00
parent bafc8ad82d
commit 98481ff0bb
1 changed files with 29 additions and 5 deletions
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34
drivers/scsi/sg.c
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@ -105,6 +105,8 @@ 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 */
@ -174,6 +176,7 @@ typedef struct sg_device { /* holds the state of each scsi generic 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 */
/* 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;
@ -222,6 +225,27 @@ static int sg_allow_access(struct file *filp, unsigned char *cmd)
return blk_verify_command(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;
@ -293,7 +317,7 @@ sg_open(struct inode *inode, struct file *filp)
}
/* Since write lock is held, no need to check sfd_list */
if (flags & O_EXCL)
sdp->exclude = 1; /* used by release lock */
set_exclude(sdp, 1);
if (sdp->detached) {
retval = -ENODEV;
@ -313,7 +337,7 @@ sg_open(struct inode *inode, struct file *filp)
retval = -ENOMEM;
sem_out:
if (flags & O_EXCL) {
sdp->exclude = 0; /* undo if error */
set_exclude(sdp, 0); /* undo if error */
up_write(&sdp->o_sem);
} else
up_read(&sdp->o_sem);
@ -340,8 +364,8 @@ sg_release(struct inode *inode, struct file *filp)
return -ENXIO;
SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));
excl = sdp->exclude;
sdp->exclude = 0;
excl = get_exclude(sdp);
set_exclude(sdp, 0);
if (excl)
up_write(&sdp->o_sem);
else
@ -2598,7 +2622,7 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v)
scsidp->lun,
scsidp->host->hostt->emulated);
seq_printf(s, " sg_tablesize=%d excl=%d\n",
sdp->sg_tablesize, sdp->exclude);
sdp->sg_tablesize, get_exclude(sdp));
sg_proc_debug_helper(s, sdp);
}
read_unlock_irqrestore(&sg_index_lock, iflags);