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Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/g…
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…it/jejb/scsi

Pull SCSI fixes from James Bottomley:
 "This is a set of four patches that revert functionality introduced in
  the merge window to sg.  The locking changes turned out to introduce
  this bug:

      [  205.372901] [ BUG: lock held when returning to user space! ]
   [...]
      [  205.373285]  #0:  (&sdp->o_sem){.+.+..}, at: [<ffffffff8161e650>] sg_open+0x3a0/0x4d0

  The fix is large, so at this late stage we'd like to revert the
  functionality and start again in the next merge window"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  [SCSI] Revert "sg: use rwsem to solve race during exclusive open"
  [SCSI] Revert "sg: no need sg_open_exclusive_lock"
  [SCSI] Revert "sg: checking sdp->detached isn't protected when open"
  [SCSI] Revert "sg: push file descriptor list locking down to per-device locking"
  • Loading branch information
Linus Torvalds committed Oct 28, 2013
2 parents 959f585 + 065b4a2 commit 5d914a9
Showing 1 changed file with 95 additions and 81 deletions.
176 changes: 95 additions & 81 deletions drivers/scsi/sg.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -105,8 +105,11 @@ 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);
static DEFINE_RWLOCK(sg_index_lock); /* Also used to lock
file descriptor list for device */

static struct class_interface sg_interface = {
.add_dev = sg_add,
Expand Down Expand Up @@ -143,7 +146,8 @@ typedef struct sg_request { /* SG_MAX_QUEUE requests outstanding per file */
} Sg_request;

typedef struct sg_fd { /* holds the state of a file descriptor */
struct list_head sfd_siblings; /* protected by sfd_lock of device */
/* 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 */
rwlock_t rq_list_lock; /* protect access to list in req_arr */
Expand All @@ -166,12 +170,13 @@ 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 */
spinlock_t sfd_lock; /* protect file descriptor list for device */
/* 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 */
char sgdebug; /* 0->off, 1->sense, 9->dump dev, 10-> all devs */
struct gendisk *disk;
Expand Down Expand Up @@ -220,14 +225,35 @@ 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;
int ret;

spin_lock_irqsave(&sdp->sfd_lock, flags);
read_lock_irqsave(&sg_index_lock, flags);
ret = list_empty(&sdp->sfds);
spin_unlock_irqrestore(&sdp->sfd_lock, flags);
read_unlock_irqrestore(&sg_index_lock, flags);
return ret;
}

Expand All @@ -239,6 +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);
Expand Down Expand Up @@ -267,52 +294,54 @@ 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)
sdp->exclude = 1; /* used by release lock */

if (sdp->detached) {
retval = -ENODEV;
goto error_out;
}
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);
}
sfp = sg_add_sfp(sdp, dev);
if (!IS_ERR(sfp))
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 = PTR_ERR(sfp);

if (flags & O_EXCL) {
sdp->exclude = 0; /* undo if error */
up_write(&sdp->o_sem);
} else
up_read(&sdp->o_sem);
set_exclude(sdp, 0); /* undo if error */
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);
Expand All @@ -329,18 +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 = sdp->exclude;
sdp->exclude = 0;
if (excl)
up_write(&sdp->o_sem);
else
up_read(&sdp->o_sem);
set_exclude(sdp, 0);
wake_up_interruptible(&sdp->o_excl_wait);

scsi_autopm_put_device(sdp->device);
kref_put(&sfp->f_ref, sg_remove_sfp);
Expand Down Expand Up @@ -1391,9 +1415,8 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
disk->first_minor = k;
sdp->disk = disk;
sdp->device = scsidp;
spin_lock_init(&sdp->sfd_lock);
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);
Expand Down Expand Up @@ -1526,13 +1549,11 @@ static void sg_remove(struct device *cl_dev, struct class_interface *cl_intf)

/* Need a write lock to set sdp->detached. */
write_lock_irqsave(&sg_index_lock, iflags);
spin_lock(&sdp->sfd_lock);
sdp->detached = 1;
list_for_each_entry(sfp, &sdp->sfds, sfd_siblings) {
wake_up_interruptible(&sfp->read_wait);
kill_fasync(&sfp->async_qp, SIGPOLL, POLL_HUP);
}
spin_unlock(&sdp->sfd_lock);
write_unlock_irqrestore(&sg_index_lock, iflags);

sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");
Expand Down Expand Up @@ -2043,7 +2064,7 @@ sg_add_sfp(Sg_device * sdp, int dev)

sfp = kzalloc(sizeof(*sfp), GFP_ATOMIC | __GFP_NOWARN);
if (!sfp)
return ERR_PTR(-ENOMEM);
return NULL;

init_waitqueue_head(&sfp->read_wait);
rwlock_init(&sfp->rq_list_lock);
Expand All @@ -2057,13 +2078,9 @@ sg_add_sfp(Sg_device * sdp, int dev)
sfp->cmd_q = SG_DEF_COMMAND_Q;
sfp->keep_orphan = SG_DEF_KEEP_ORPHAN;
sfp->parentdp = sdp;
spin_lock_irqsave(&sdp->sfd_lock, iflags);
if (sdp->detached) {
spin_unlock_irqrestore(&sdp->sfd_lock, iflags);
return ERR_PTR(-ENODEV);
}
write_lock_irqsave(&sg_index_lock, iflags);
list_add_tail(&sfp->sfd_siblings, &sdp->sfds);
spin_unlock_irqrestore(&sdp->sfd_lock, iflags);
write_unlock_irqrestore(&sg_index_lock, iflags);
SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));
if (unlikely(sg_big_buff != def_reserved_size))
sg_big_buff = def_reserved_size;
Expand Down Expand Up @@ -2113,9 +2130,10 @@ static void sg_remove_sfp(struct kref *kref)
struct sg_device *sdp = sfp->parentdp;
unsigned long iflags;

spin_lock_irqsave(&sdp->sfd_lock, iflags);
write_lock_irqsave(&sg_index_lock, iflags);
list_del(&sfp->sfd_siblings);
spin_unlock_irqrestore(&sdp->sfd_lock, iflags);
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);
Expand Down Expand Up @@ -2502,7 +2520,7 @@ static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v)
return 0;
}

/* must be called while holding sg_index_lock and sfd_lock */
/* must be called while holding sg_index_lock */
static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
{
int k, m, new_interface, blen, usg;
Expand Down Expand Up @@ -2587,26 +2605,22 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v)

read_lock_irqsave(&sg_index_lock, iflags);
sdp = it ? sg_lookup_dev(it->index) : NULL;
if (sdp) {
spin_lock(&sdp->sfd_lock);
if (!list_empty(&sdp->sfds)) {
struct scsi_device *scsidp = sdp->device;
if (sdp && !list_empty(&sdp->sfds)) {
struct scsi_device *scsidp = sdp->device;

seq_printf(s, " >>> device=%s ", sdp->disk->disk_name);
if (sdp->detached)
seq_printf(s, "detached pending close ");
else
seq_printf
(s, "scsi%d chan=%d id=%d lun=%d em=%d",
scsidp->host->host_no,
scsidp->channel, scsidp->id,
scsidp->lun,
scsidp->host->hostt->emulated);
seq_printf(s, " sg_tablesize=%d excl=%d\n",
sdp->sg_tablesize, sdp->exclude);
sg_proc_debug_helper(s, sdp);
}
spin_unlock(&sdp->sfd_lock);
seq_printf(s, " >>> device=%s ", sdp->disk->disk_name);
if (sdp->detached)
seq_printf(s, "detached pending close ");
else
seq_printf
(s, "scsi%d chan=%d id=%d lun=%d em=%d",
scsidp->host->host_no,
scsidp->channel, scsidp->id,
scsidp->lun,
scsidp->host->hostt->emulated);
seq_printf(s, " sg_tablesize=%d excl=%d\n",
sdp->sg_tablesize, get_exclude(sdp));
sg_proc_debug_helper(s, sdp);
}
read_unlock_irqrestore(&sg_index_lock, iflags);
return 0;
Expand Down

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