Revision bba0bdd7ad4713d82338bcd9b72d57e9335a664b authored by Bart Van Assche on 04 March 2015, 09:31:47 UTC, committed by James Bottomley on 08 April 2015, 16:41:41 UTC
SCSI transport drivers and SCSI LLDs block a SCSI device if the transport layer is not operational. This means that in this state no requests should be processed, even if the REQ_PREEMPT flag has been set. This patch avoids that a rescan shortly after a cable pull sporadically triggers the following kernel oops: BUG: unable to handle kernel paging request at ffffc9001a6bc084 IP: [<ffffffffa04e08f2>] mlx4_ib_post_send+0xd2/0xb30 [mlx4_ib] Process rescan-scsi-bus (pid: 9241, threadinfo ffff88053484a000, task ffff880534aae100) Call Trace: [<ffffffffa0718135>] srp_post_send+0x65/0x70 [ib_srp] [<ffffffffa071b9df>] srp_queuecommand+0x1cf/0x3e0 [ib_srp] [<ffffffffa0001ff1>] scsi_dispatch_cmd+0x101/0x280 [scsi_mod] [<ffffffffa0009ad1>] scsi_request_fn+0x411/0x4d0 [scsi_mod] [<ffffffff81223b37>] __blk_run_queue+0x27/0x30 [<ffffffff8122a8d2>] blk_execute_rq_nowait+0x82/0x110 [<ffffffff8122a9c2>] blk_execute_rq+0x62/0xf0 [<ffffffffa000b0e8>] scsi_execute+0xe8/0x190 [scsi_mod] [<ffffffffa000b2f3>] scsi_execute_req+0xa3/0x130 [scsi_mod] [<ffffffffa000c1aa>] scsi_probe_lun+0x17a/0x450 [scsi_mod] [<ffffffffa000ce86>] scsi_probe_and_add_lun+0x156/0x480 [scsi_mod] [<ffffffffa000dc2f>] __scsi_scan_target+0xdf/0x1f0 [scsi_mod] [<ffffffffa000dfa3>] scsi_scan_host_selected+0x183/0x1c0 [scsi_mod] [<ffffffffa000edfb>] scsi_scan+0xdb/0xe0 [scsi_mod] [<ffffffffa000ee13>] store_scan+0x13/0x20 [scsi_mod] [<ffffffff811c8d9b>] sysfs_write_file+0xcb/0x160 [<ffffffff811589de>] vfs_write+0xce/0x140 [<ffffffff81158b53>] sys_write+0x53/0xa0 [<ffffffff81464592>] system_call_fastpath+0x16/0x1b [<00007f611c9d9300>] 0x7f611c9d92ff Reported-by: Max Gurtuvoy <maxg@mellanox.com> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com> Reviewed-by: Mike Christie <michaelc@cs.wisc.edu> Cc: <stable@vger.kernel.org> Signed-off-by: James Bottomley <JBottomley@Odin.com>
1 parent 2e7cee0
lockref.c
#include <linux/export.h>
#include <linux/lockref.h>
#if USE_CMPXCHG_LOCKREF
/*
* Allow weakly-ordered memory architectures to provide barrier-less
* cmpxchg semantics for lockref updates.
*/
#ifndef cmpxchg64_relaxed
# define cmpxchg64_relaxed cmpxchg64
#endif
/*
* Note that the "cmpxchg()" reloads the "old" value for the
* failure case.
*/
#define CMPXCHG_LOOP(CODE, SUCCESS) do { \
struct lockref old; \
BUILD_BUG_ON(sizeof(old) != 8); \
old.lock_count = ACCESS_ONCE(lockref->lock_count); \
while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \
struct lockref new = old, prev = old; \
CODE \
old.lock_count = cmpxchg64_relaxed(&lockref->lock_count, \
old.lock_count, \
new.lock_count); \
if (likely(old.lock_count == prev.lock_count)) { \
SUCCESS; \
} \
cpu_relax_lowlatency(); \
} \
} while (0)
#else
#define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0)
#endif
/**
* lockref_get - Increments reference count unconditionally
* @lockref: pointer to lockref structure
*
* This operation is only valid if you already hold a reference
* to the object, so you know the count cannot be zero.
*/
void lockref_get(struct lockref *lockref)
{
CMPXCHG_LOOP(
new.count++;
,
return;
);
spin_lock(&lockref->lock);
lockref->count++;
spin_unlock(&lockref->lock);
}
EXPORT_SYMBOL(lockref_get);
/**
* lockref_get_not_zero - Increments count unless the count is 0 or dead
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count was zero
*/
int lockref_get_not_zero(struct lockref *lockref)
{
int retval;
CMPXCHG_LOOP(
new.count++;
if (old.count <= 0)
return 0;
,
return 1;
);
spin_lock(&lockref->lock);
retval = 0;
if (lockref->count > 0) {
lockref->count++;
retval = 1;
}
spin_unlock(&lockref->lock);
return retval;
}
EXPORT_SYMBOL(lockref_get_not_zero);
/**
* lockref_get_or_lock - Increments count unless the count is 0 or dead
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count was zero
* and we got the lock instead.
*/
int lockref_get_or_lock(struct lockref *lockref)
{
CMPXCHG_LOOP(
new.count++;
if (old.count <= 0)
break;
,
return 1;
);
spin_lock(&lockref->lock);
if (lockref->count <= 0)
return 0;
lockref->count++;
spin_unlock(&lockref->lock);
return 1;
}
EXPORT_SYMBOL(lockref_get_or_lock);
/**
* lockref_put_return - Decrement reference count if possible
* @lockref: pointer to lockref structure
*
* Decrement the reference count and return the new value.
* If the lockref was dead or locked, return an error.
*/
int lockref_put_return(struct lockref *lockref)
{
CMPXCHG_LOOP(
new.count--;
if (old.count <= 0)
return -1;
,
return new.count;
);
return -1;
}
EXPORT_SYMBOL(lockref_put_return);
/**
* lockref_put_or_lock - decrements count unless count <= 1 before decrement
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
*/
int lockref_put_or_lock(struct lockref *lockref)
{
CMPXCHG_LOOP(
new.count--;
if (old.count <= 1)
break;
,
return 1;
);
spin_lock(&lockref->lock);
if (lockref->count <= 1)
return 0;
lockref->count--;
spin_unlock(&lockref->lock);
return 1;
}
EXPORT_SYMBOL(lockref_put_or_lock);
/**
* lockref_mark_dead - mark lockref dead
* @lockref: pointer to lockref structure
*/
void lockref_mark_dead(struct lockref *lockref)
{
assert_spin_locked(&lockref->lock);
lockref->count = -128;
}
EXPORT_SYMBOL(lockref_mark_dead);
/**
* lockref_get_not_dead - Increments count unless the ref is dead
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if lockref was dead
*/
int lockref_get_not_dead(struct lockref *lockref)
{
int retval;
CMPXCHG_LOOP(
new.count++;
if (old.count < 0)
return 0;
,
return 1;
);
spin_lock(&lockref->lock);
retval = 0;
if (lockref->count >= 0) {
lockref->count++;
retval = 1;
}
spin_unlock(&lockref->lock);
return retval;
}
EXPORT_SYMBOL(lockref_get_not_dead);
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