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.
The patch is available here:
git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi.git scsi-fixes
The short changelog is:
James Bottomley (4):
Revert "sg: use rwsem to solve race during exclusive open"
Revert "sg: no need sg_open_exclusive_lock"
Revert "sg: checking sdp->detached isn't protected when open"
Revert "sg: push file descriptor list locking down to per-device locking"
And the diffstat:
drivers/scsi/sg.c | 176 +++++++++++++++++++++++++++++-------------------------
1 file changed, 95 insertions(+), 81 deletions(-)
With full diff below.
James
---
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 5cbc4bb..df5e961 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -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,
@@ -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 */
@@ -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;
@@ -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;
}
@@ -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);
@@ -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);
@@ -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);
@@ -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);
@@ -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");
@@ -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);
@@ -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;
@@ -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);
@@ -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;
@@ -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;
--
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