| Message ID | 20191008075022.30055-6-dgilbert@interlog.com (mailing list archive) |
|---|---|
| State | Deferred |
| Headers | show |
| Series | sg: add v4 interface | expand |
On 10/8/19 9:50 AM, Douglas Gilbert wrote: > Introduce bitops in sg_device to replace an atomic, a bool and a > char. That char (sgdebug) had been reduced to only two states. > Add some associated macros to make the code a little clearer. > > Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> > --- > drivers/scsi/sg.c | 104 +++++++++++++++++++++++----------------------- > 1 file changed, 53 insertions(+), 51 deletions(-) > > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > index 9aa1b1030033..97ce84f0c51b 100644 > --- a/drivers/scsi/sg.c > +++ b/drivers/scsi/sg.c > @@ -74,6 +74,11 @@ static char *sg_version_date = "20190606"; > > #define SG_DEFAULT_TIMEOUT mult_frac(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ) > > +/* Bit positions (flags) for sg_device::fdev_bm bitmask follow */ > +#define SG_FDEV_EXCLUDE 0 /* have fd open with O_EXCL */ > +#define SG_FDEV_DETACHING 1 /* may be unexpected device removal */ > +#define SG_FDEV_LOG_SENSE 2 /* set by ioctl(SG_SET_DEBUG) */ > + > int sg_big_buff = SG_DEF_RESERVED_SIZE; > /* N.B. This variable is readable and writeable via > /proc/scsi/sg/def_reserved_size . Each time sg_open() is called a buffer > @@ -155,14 +160,12 @@ struct sg_device { /* holds the state of each scsi generic device */ > struct scsi_device *device; > wait_queue_head_t open_wait; /* queue open() when O_EXCL present */ > struct mutex open_rel_lock; /* held when in open() or release() */ > - int sg_tablesize; /* adapter's max scatter-gather table size */ > - u32 index; /* device index number */ > struct list_head sfds; > rwlock_t sfd_lock; /* protect access to sfd list */ > - atomic_t detaching; /* 0->device usable, 1->device detaching */ > - bool exclude; /* 1->open(O_EXCL) succeeded and is active */ > + int sg_tablesize; /* adapter's max scatter-gather table size */ > + u32 index; /* device index number */ > int open_cnt; /* count of opens (perhaps < num(sfds) ) */ > - char sgdebug; /* 0->off, 1->sense, 9->dump dev, 10-> all devs */ > + unsigned long fdev_bm[1]; /* see SG_FDEV_* defines above */ > struct gendisk *disk; > struct cdev * cdev; /* char_dev [sysfs: /sys/cdev/major/sg<n>] */ > struct kref d_ref; > @@ -200,6 +203,9 @@ static void sg_device_destroy(struct kref *kref); > #define SZ_SG_IO_HDR ((int)sizeof(struct sg_io_hdr)) /* v3 header */ > #define SZ_SG_REQ_INFO ((int)sizeof(struct sg_req_info)) > > +#define SG_IS_DETACHING(sdp) test_bit(SG_FDEV_DETACHING, (sdp)->fdev_bm) > +#define SG_HAVE_EXCLUDE(sdp) test_bit(SG_FDEV_EXCLUDE, (sdp)->fdev_bm) > + > /* > * Kernel needs to be built with CONFIG_SCSI_LOGGING to see log messages. > * 'depth' is a number between 1 (most severe) and 7 (most noisy, most > @@ -273,26 +279,26 @@ sg_wait_open_event(struct sg_device *sdp, bool o_excl) > while (sdp->open_cnt > 0) { > mutex_unlock(&sdp->open_rel_lock); > retval = wait_event_interruptible(sdp->open_wait, > - (atomic_read(&sdp->detaching) || > + (SG_IS_DETACHING(sdp) || > !sdp->open_cnt)); > mutex_lock(&sdp->open_rel_lock); > > if (retval) /* -ERESTARTSYS */ > return retval; > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > } > } else { > - while (sdp->exclude) { > + while (SG_HAVE_EXCLUDE(sdp)) { > mutex_unlock(&sdp->open_rel_lock); > retval = wait_event_interruptible(sdp->open_wait, > - (atomic_read(&sdp->detaching) || > - !sdp->exclude)); > + (SG_IS_DETACHING(sdp) || > + !SG_HAVE_EXCLUDE(sdp))); > mutex_lock(&sdp->open_rel_lock); > > if (retval) /* -ERESTARTSYS */ > return retval; > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > } > } > @@ -354,7 +360,7 @@ sg_open(struct inode *inode, struct file *filp) > goto error_mutex_locked; > } > } else { > - if (sdp->exclude) { > + if (SG_HAVE_EXCLUDE(sdp)) { > retval = -EBUSY; > goto error_mutex_locked; > } > @@ -367,10 +373,10 @@ sg_open(struct inode *inode, struct file *filp) > > /* N.B. at this point we are holding the open_rel_lock */ > if (o_excl) > - sdp->exclude = true; > + set_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm); > > if (sdp->open_cnt < 1) { /* no existing opens */ > - sdp->sgdebug = 0; > + clear_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm); > q = sdp->device->request_queue; > sdp->sg_tablesize = queue_max_segments(q); > } > @@ -393,8 +399,8 @@ sg_open(struct inode *inode, struct file *filp) > return retval; > > out_undo: > - if (o_excl) { > - sdp->exclude = false; /* undo if error */ > + if (o_excl) { /* undo if error */ > + clear_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm); > wake_up_interruptible(&sdp->open_wait); > } > error_mutex_locked: > @@ -428,12 +434,10 @@ sg_release(struct inode *inode, struct file *filp) > > /* possibly many open()s waiting on exlude clearing, start many; > * only open(O_EXCL)s wait on 0==open_cnt so only start one */ > - if (sdp->exclude) { > - sdp->exclude = false; > + if (test_and_clear_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm)) > wake_up_interruptible_all(&sdp->open_wait); > - } else if (0 == sdp->open_cnt) { > + else if (sdp->open_cnt == 0) > wake_up_interruptible(&sdp->open_wait); > - } > mutex_unlock(&sdp->open_rel_lock); > return 0; > } > @@ -467,7 +471,7 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos) > SG_LOG(3, sfp, "%s: write(3rd arg) count=%d\n", __func__, (int)count); > if (!sdp) > return -ENXIO; > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > if (!((filp->f_flags & O_NONBLOCK) || > scsi_block_when_processing_errors(sdp->device))) > @@ -666,7 +670,7 @@ sg_common_write(struct sg_fd *sfp, struct sg_request *srp, > sg_remove_request(sfp, srp); > return k; /* probably out of space --> ENOMEM */ > } > - if (atomic_read(&sdp->detaching)) { > + if (SG_IS_DETACHING(sdp)) { > if (srp->bio) { > scsi_req_free_cmd(scsi_req(srp->rq)); > blk_put_request(srp->rq); > @@ -831,7 +835,7 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) > } > srp = sg_get_rq_mark(sfp, req_pack_id); > if (!srp) { /* now wait on packet to arrive */ > - if (atomic_read(&sdp->detaching)) { > + if (SG_IS_DETACHING(sdp)) { > retval = -ENODEV; > goto free_old_hdr; > } > @@ -840,9 +844,9 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) > goto free_old_hdr; > } > retval = wait_event_interruptible(sfp->read_wait, > - (atomic_read(&sdp->detaching) || > + (SG_IS_DETACHING(sdp) || > (srp = sg_get_rq_mark(sfp, req_pack_id)))); > - if (atomic_read(&sdp->detaching)) { > + if (SG_IS_DETACHING(sdp)) { > retval = -ENODEV; > goto free_old_hdr; > } > @@ -997,7 +1001,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) > > switch (cmd_in) { > case SG_IO: > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > if (!scsi_block_when_processing_errors(sdp->device)) > return -ENXIO; > @@ -1008,8 +1012,8 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) > if (result < 0) > return result; > result = wait_event_interruptible(sfp->read_wait, > - (srp_done(sfp, srp) || atomic_read(&sdp->detaching))); > - if (atomic_read(&sdp->detaching)) > + (srp_done(sfp, srp) || SG_IS_DETACHING(sdp))); > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > write_lock_irq(&sfp->rq_list_lock); > if (srp->done) { > @@ -1052,7 +1056,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) > else { > sg_scsi_id_t __user *sg_idp = p; > > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > __put_user((int) sdp->device->host->host_no, > &sg_idp->host_no); > @@ -1176,18 +1180,18 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) > return result; > } > case SG_EMULATED_HOST: > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > return put_user(sdp->device->host->hostt->emulated, ip); > case SCSI_IOCTL_SEND_COMMAND: > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > return sg_scsi_ioctl(sdp->device->request_queue, NULL, filp->f_mode, p); > case SG_SET_DEBUG: > result = get_user(val, ip); > if (result) > return result; > - sdp->sgdebug = (char) val; > + assign_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm, val); > return 0; > case BLKSECTGET: > return put_user(max_sectors_bytes(sdp->device->request_queue), > @@ -1208,7 +1212,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) > case SCSI_IOCTL_PROBE_HOST: > case SG_GET_TRANSFORM: > case SG_SCSI_RESET: > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > return -ENODEV; > break; > default: > @@ -1271,7 +1275,7 @@ sg_poll(struct file *filp, poll_table * wait) > } > read_unlock_irqrestore(&sfp->rq_list_lock, iflags); > > - if (sfp->parentdp && atomic_read(&sfp->parentdp->detaching)) { > + if (sfp->parentdp && SG_IS_DETACHING(sfp->parentdp)) { > p_res |= EPOLLHUP; > } else if (!sfp->cmd_q) { > if (count == 0) > @@ -1419,7 +1423,7 @@ sg_rq_end_io(struct request *rq, blk_status_t status) > return; > > sdp = sfp->parentdp; > - if (unlikely(atomic_read(&sdp->detaching))) > + if (unlikely(SG_IS_DETACHING(sdp))) > pr_info("%s: device detaching\n", __func__); > > sense = req->sense; > @@ -1440,9 +1444,9 @@ sg_rq_end_io(struct request *rq, blk_status_t status) > srp->header.msg_status = msg_byte(result); > srp->header.host_status = host_byte(result); > srp->header.driver_status = driver_byte(result); > - if ((sdp->sgdebug > 0) && > - ((CHECK_CONDITION == srp->header.masked_status) || > - (COMMAND_TERMINATED == srp->header.masked_status))) > + if (test_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm) && > + (srp->header.masked_status == CHECK_CONDITION || > + srp->header.masked_status == COMMAND_TERMINATED)) > __scsi_print_sense(sdp->device, __func__, sense, > SCSI_SENSE_BUFFERSIZE); > > @@ -1557,7 +1561,7 @@ sg_alloc(struct gendisk *disk, struct scsi_device *scsidp) > mutex_init(&sdp->open_rel_lock); > INIT_LIST_HEAD(&sdp->sfds); > init_waitqueue_head(&sdp->open_wait); > - atomic_set(&sdp->detaching, 0); > + clear_bit(SG_FDEV_DETACHING, sdp->fdev_bm); > rwlock_init(&sdp->sfd_lock); > sdp->sg_tablesize = queue_max_segments(q); > sdp->index = k; > @@ -1682,13 +1686,11 @@ sg_remove_device(struct device *cl_dev, struct class_interface *cl_intf) > struct sg_device *sdp = dev_get_drvdata(cl_dev); > unsigned long iflags; > struct sg_fd *sfp; > - int val; > > if (!sdp) > return; > - /* want sdp->detaching non-zero as soon as possible */ > - val = atomic_inc_return(&sdp->detaching); > - if (val > 1) > + /* set this flag as soon as possible as it could be a surprise */ > + if (test_and_set_bit(SG_FDEV_DETACHING, sdp->fdev_bm)) > return; /* only want to do following once per device */ > > SCSI_LOG_TIMEOUT(3, sdev_printk(KERN_INFO, sdp->device, > @@ -2218,7 +2220,7 @@ sg_add_sfp(struct sg_device *sdp) > sfp->keep_orphan = SG_DEF_KEEP_ORPHAN; > sfp->parentdp = sdp; > write_lock_irqsave(&sdp->sfd_lock, iflags); > - if (atomic_read(&sdp->detaching)) { > + if (SG_IS_DETACHING(sdp)) { > write_unlock_irqrestore(&sdp->sfd_lock, iflags); > kfree(sfp); > return ERR_PTR(-ENODEV); > @@ -2315,8 +2317,8 @@ sg_get_dev(int dev) > sdp = sg_lookup_dev(dev); > if (!sdp) > sdp = ERR_PTR(-ENXIO); > - else if (atomic_read(&sdp->detaching)) { > - /* If sdp->detaching, then the refcount may already be 0, in > + else if (SG_IS_DETACHING(sdp)) { > + /* If detaching, then the refcount may already be 0, in > * which case it would be a bug to do kref_get(). > */ > sdp = ERR_PTR(-ENODEV); > @@ -2530,8 +2532,7 @@ sg_proc_seq_show_dev(struct seq_file *s, void *v) > > read_lock_irqsave(&sg_index_lock, iflags); > sdp = it ? sg_lookup_dev(it->index) : NULL; > - if ((NULL == sdp) || (NULL == sdp->device) || > - (atomic_read(&sdp->detaching))) > + if (!sdp || !sdp->device || SG_IS_DETACHING(sdp)) > seq_puts(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n"); > else { > scsidp = sdp->device; > @@ -2558,7 +2559,7 @@ sg_proc_seq_show_devstrs(struct seq_file *s, void *v) > read_lock_irqsave(&sg_index_lock, iflags); > sdp = it ? sg_lookup_dev(it->index) : NULL; > scsidp = sdp ? sdp->device : NULL; > - if (sdp && scsidp && (!atomic_read(&sdp->detaching))) > + if (sdp && scsidp && !SG_IS_DETACHING(sdp)) > seq_printf(s, "%8.8s\t%16.16s\t%4.4s\n", > scsidp->vendor, scsidp->model, scsidp->rev); > else > @@ -2650,7 +2651,7 @@ sg_proc_seq_show_debug(struct seq_file *s, void *v) > read_lock(&sdp->sfd_lock); > if (!list_empty(&sdp->sfds)) { > seq_printf(s, " >>> device=%s ", sdp->disk->disk_name); > - if (atomic_read(&sdp->detaching)) > + if (SG_IS_DETACHING(sdp)) > seq_puts(s, "detaching pending close "); > else if (sdp->device) { > struct scsi_device *scsidp = sdp->device; > @@ -2662,7 +2663,8 @@ sg_proc_seq_show_debug(struct seq_file *s, void *v) > scsidp->host->hostt->emulated); > } > seq_printf(s, " sg_tablesize=%d excl=%d open_cnt=%d\n", > - sdp->sg_tablesize, sdp->exclude, sdp->open_cnt); > + sdp->sg_tablesize, SG_HAVE_EXCLUDE(sdp), > + sdp->open_cnt); > sg_proc_debug_helper(s, sdp); > } > read_unlock(&sdp->sfd_lock); > One thing to keep in mind here is that 'set_bit()' is not atomic; it needs to be followed by a memory barrier or being replaced by test_and_set_bit() if possible. Please audit the code if that poses a problem. Cheers, Hannes
On 2019-10-18 6:05 a.m., Hannes Reinecke wrote: > On 10/8/19 9:50 AM, Douglas Gilbert wrote: >> Introduce bitops in sg_device to replace an atomic, a bool and a >> char. That char (sgdebug) had been reduced to only two states. >> Add some associated macros to make the code a little clearer. >> >> Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> >> --- >> drivers/scsi/sg.c | 104 +++++++++++++++++++++++----------------------- >> 1 file changed, 53 insertions(+), 51 deletions(-) >> >> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c >> index 9aa1b1030033..97ce84f0c51b 100644 >> --- a/drivers/scsi/sg.c >> +++ b/drivers/scsi/sg.c >> @@ -74,6 +74,11 @@ static char *sg_version_date = "20190606"; >> >> #define SG_DEFAULT_TIMEOUT mult_frac(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ) >> >> +/* Bit positions (flags) for sg_device::fdev_bm bitmask follow */ >> +#define SG_FDEV_EXCLUDE 0 /* have fd open with O_EXCL */ >> +#define SG_FDEV_DETACHING 1 /* may be unexpected device removal */ >> +#define SG_FDEV_LOG_SENSE 2 /* set by ioctl(SG_SET_DEBUG) */ >> + >> int sg_big_buff = SG_DEF_RESERVED_SIZE; >> /* N.B. This variable is readable and writeable via >> /proc/scsi/sg/def_reserved_size . Each time sg_open() is called a buffer >> @@ -155,14 +160,12 @@ struct sg_device { /* holds the state of each scsi generic device */ >> struct scsi_device *device; >> wait_queue_head_t open_wait; /* queue open() when O_EXCL present */ >> struct mutex open_rel_lock; /* held when in open() or release() */ >> - int sg_tablesize; /* adapter's max scatter-gather table size */ >> - u32 index; /* device index number */ >> struct list_head sfds; >> rwlock_t sfd_lock; /* protect access to sfd list */ >> - atomic_t detaching; /* 0->device usable, 1->device detaching */ >> - bool exclude; /* 1->open(O_EXCL) succeeded and is active */ >> + int sg_tablesize; /* adapter's max scatter-gather table size */ >> + u32 index; /* device index number */ >> int open_cnt; /* count of opens (perhaps < num(sfds) ) */ >> - char sgdebug; /* 0->off, 1->sense, 9->dump dev, 10-> all devs */ >> + unsigned long fdev_bm[1]; /* see SG_FDEV_* defines above */ >> struct gendisk *disk; >> struct cdev * cdev; /* char_dev [sysfs: /sys/cdev/major/sg<n>] */ >> struct kref d_ref; >> @@ -200,6 +203,9 @@ static void sg_device_destroy(struct kref *kref); >> #define SZ_SG_IO_HDR ((int)sizeof(struct sg_io_hdr)) /* v3 header */ >> #define SZ_SG_REQ_INFO ((int)sizeof(struct sg_req_info)) >> >> +#define SG_IS_DETACHING(sdp) test_bit(SG_FDEV_DETACHING, (sdp)->fdev_bm) >> +#define SG_HAVE_EXCLUDE(sdp) test_bit(SG_FDEV_EXCLUDE, (sdp)->fdev_bm) >> + >> /* >> * Kernel needs to be built with CONFIG_SCSI_LOGGING to see log messages. >> * 'depth' is a number between 1 (most severe) and 7 (most noisy, most >> @@ -273,26 +279,26 @@ sg_wait_open_event(struct sg_device *sdp, bool o_excl) >> while (sdp->open_cnt > 0) { >> mutex_unlock(&sdp->open_rel_lock); >> retval = wait_event_interruptible(sdp->open_wait, >> - (atomic_read(&sdp->detaching) || >> + (SG_IS_DETACHING(sdp) || >> !sdp->open_cnt)); >> mutex_lock(&sdp->open_rel_lock); >> >> if (retval) /* -ERESTARTSYS */ >> return retval; >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> } >> } else { >> - while (sdp->exclude) { >> + while (SG_HAVE_EXCLUDE(sdp)) { >> mutex_unlock(&sdp->open_rel_lock); >> retval = wait_event_interruptible(sdp->open_wait, >> - (atomic_read(&sdp->detaching) || >> - !sdp->exclude)); >> + (SG_IS_DETACHING(sdp) || >> + !SG_HAVE_EXCLUDE(sdp))); >> mutex_lock(&sdp->open_rel_lock); >> >> if (retval) /* -ERESTARTSYS */ >> return retval; >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> } >> } >> @@ -354,7 +360,7 @@ sg_open(struct inode *inode, struct file *filp) >> goto error_mutex_locked; >> } >> } else { >> - if (sdp->exclude) { >> + if (SG_HAVE_EXCLUDE(sdp)) { >> retval = -EBUSY; >> goto error_mutex_locked; >> } >> @@ -367,10 +373,10 @@ sg_open(struct inode *inode, struct file *filp) >> >> /* N.B. at this point we are holding the open_rel_lock */ >> if (o_excl) >> - sdp->exclude = true; >> + set_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm); >> >> if (sdp->open_cnt < 1) { /* no existing opens */ >> - sdp->sgdebug = 0; >> + clear_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm); >> q = sdp->device->request_queue; >> sdp->sg_tablesize = queue_max_segments(q); >> } >> @@ -393,8 +399,8 @@ sg_open(struct inode *inode, struct file *filp) >> return retval; >> >> out_undo: >> - if (o_excl) { >> - sdp->exclude = false; /* undo if error */ >> + if (o_excl) { /* undo if error */ >> + clear_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm); >> wake_up_interruptible(&sdp->open_wait); >> } >> error_mutex_locked: >> @@ -428,12 +434,10 @@ sg_release(struct inode *inode, struct file *filp) >> >> /* possibly many open()s waiting on exlude clearing, start many; >> * only open(O_EXCL)s wait on 0==open_cnt so only start one */ >> - if (sdp->exclude) { >> - sdp->exclude = false; >> + if (test_and_clear_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm)) >> wake_up_interruptible_all(&sdp->open_wait); >> - } else if (0 == sdp->open_cnt) { >> + else if (sdp->open_cnt == 0) >> wake_up_interruptible(&sdp->open_wait); >> - } >> mutex_unlock(&sdp->open_rel_lock); >> return 0; >> } >> @@ -467,7 +471,7 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos) >> SG_LOG(3, sfp, "%s: write(3rd arg) count=%d\n", __func__, (int)count); >> if (!sdp) >> return -ENXIO; >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> if (!((filp->f_flags & O_NONBLOCK) || >> scsi_block_when_processing_errors(sdp->device))) >> @@ -666,7 +670,7 @@ sg_common_write(struct sg_fd *sfp, struct sg_request *srp, >> sg_remove_request(sfp, srp); >> return k; /* probably out of space --> ENOMEM */ >> } >> - if (atomic_read(&sdp->detaching)) { >> + if (SG_IS_DETACHING(sdp)) { >> if (srp->bio) { >> scsi_req_free_cmd(scsi_req(srp->rq)); >> blk_put_request(srp->rq); >> @@ -831,7 +835,7 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) >> } >> srp = sg_get_rq_mark(sfp, req_pack_id); >> if (!srp) { /* now wait on packet to arrive */ >> - if (atomic_read(&sdp->detaching)) { >> + if (SG_IS_DETACHING(sdp)) { >> retval = -ENODEV; >> goto free_old_hdr; >> } >> @@ -840,9 +844,9 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) >> goto free_old_hdr; >> } >> retval = wait_event_interruptible(sfp->read_wait, >> - (atomic_read(&sdp->detaching) || >> + (SG_IS_DETACHING(sdp) || >> (srp = sg_get_rq_mark(sfp, req_pack_id)))); >> - if (atomic_read(&sdp->detaching)) { >> + if (SG_IS_DETACHING(sdp)) { >> retval = -ENODEV; >> goto free_old_hdr; >> } >> @@ -997,7 +1001,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) >> >> switch (cmd_in) { >> case SG_IO: >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> if (!scsi_block_when_processing_errors(sdp->device)) >> return -ENXIO; >> @@ -1008,8 +1012,8 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) >> if (result < 0) >> return result; >> result = wait_event_interruptible(sfp->read_wait, >> - (srp_done(sfp, srp) || atomic_read(&sdp->detaching))); >> - if (atomic_read(&sdp->detaching)) >> + (srp_done(sfp, srp) || SG_IS_DETACHING(sdp))); >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> write_lock_irq(&sfp->rq_list_lock); >> if (srp->done) { >> @@ -1052,7 +1056,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) >> else { >> sg_scsi_id_t __user *sg_idp = p; >> >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> __put_user((int) sdp->device->host->host_no, >> &sg_idp->host_no); >> @@ -1176,18 +1180,18 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) >> return result; >> } >> case SG_EMULATED_HOST: >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> return put_user(sdp->device->host->hostt->emulated, ip); >> case SCSI_IOCTL_SEND_COMMAND: >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> return sg_scsi_ioctl(sdp->device->request_queue, NULL, filp->f_mode, p); >> case SG_SET_DEBUG: >> result = get_user(val, ip); >> if (result) >> return result; >> - sdp->sgdebug = (char) val; >> + assign_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm, val); >> return 0; >> case BLKSECTGET: >> return put_user(max_sectors_bytes(sdp->device->request_queue), >> @@ -1208,7 +1212,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) >> case SCSI_IOCTL_PROBE_HOST: >> case SG_GET_TRANSFORM: >> case SG_SCSI_RESET: >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> return -ENODEV; >> break; >> default: >> @@ -1271,7 +1275,7 @@ sg_poll(struct file *filp, poll_table * wait) >> } >> read_unlock_irqrestore(&sfp->rq_list_lock, iflags); >> >> - if (sfp->parentdp && atomic_read(&sfp->parentdp->detaching)) { >> + if (sfp->parentdp && SG_IS_DETACHING(sfp->parentdp)) { >> p_res |= EPOLLHUP; >> } else if (!sfp->cmd_q) { >> if (count == 0) >> @@ -1419,7 +1423,7 @@ sg_rq_end_io(struct request *rq, blk_status_t status) >> return; >> >> sdp = sfp->parentdp; >> - if (unlikely(atomic_read(&sdp->detaching))) >> + if (unlikely(SG_IS_DETACHING(sdp))) >> pr_info("%s: device detaching\n", __func__); >> >> sense = req->sense; >> @@ -1440,9 +1444,9 @@ sg_rq_end_io(struct request *rq, blk_status_t status) >> srp->header.msg_status = msg_byte(result); >> srp->header.host_status = host_byte(result); >> srp->header.driver_status = driver_byte(result); >> - if ((sdp->sgdebug > 0) && >> - ((CHECK_CONDITION == srp->header.masked_status) || >> - (COMMAND_TERMINATED == srp->header.masked_status))) >> + if (test_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm) && >> + (srp->header.masked_status == CHECK_CONDITION || >> + srp->header.masked_status == COMMAND_TERMINATED)) >> __scsi_print_sense(sdp->device, __func__, sense, >> SCSI_SENSE_BUFFERSIZE); >> >> @@ -1557,7 +1561,7 @@ sg_alloc(struct gendisk *disk, struct scsi_device *scsidp) >> mutex_init(&sdp->open_rel_lock); >> INIT_LIST_HEAD(&sdp->sfds); >> init_waitqueue_head(&sdp->open_wait); >> - atomic_set(&sdp->detaching, 0); >> + clear_bit(SG_FDEV_DETACHING, sdp->fdev_bm); >> rwlock_init(&sdp->sfd_lock); >> sdp->sg_tablesize = queue_max_segments(q); >> sdp->index = k; >> @@ -1682,13 +1686,11 @@ sg_remove_device(struct device *cl_dev, struct class_interface *cl_intf) >> struct sg_device *sdp = dev_get_drvdata(cl_dev); >> unsigned long iflags; >> struct sg_fd *sfp; >> - int val; >> >> if (!sdp) >> return; >> - /* want sdp->detaching non-zero as soon as possible */ >> - val = atomic_inc_return(&sdp->detaching); >> - if (val > 1) >> + /* set this flag as soon as possible as it could be a surprise */ >> + if (test_and_set_bit(SG_FDEV_DETACHING, sdp->fdev_bm)) >> return; /* only want to do following once per device */ >> >> SCSI_LOG_TIMEOUT(3, sdev_printk(KERN_INFO, sdp->device, >> @@ -2218,7 +2220,7 @@ sg_add_sfp(struct sg_device *sdp) >> sfp->keep_orphan = SG_DEF_KEEP_ORPHAN; >> sfp->parentdp = sdp; >> write_lock_irqsave(&sdp->sfd_lock, iflags); >> - if (atomic_read(&sdp->detaching)) { >> + if (SG_IS_DETACHING(sdp)) { >> write_unlock_irqrestore(&sdp->sfd_lock, iflags); >> kfree(sfp); >> return ERR_PTR(-ENODEV); >> @@ -2315,8 +2317,8 @@ sg_get_dev(int dev) >> sdp = sg_lookup_dev(dev); >> if (!sdp) >> sdp = ERR_PTR(-ENXIO); >> - else if (atomic_read(&sdp->detaching)) { >> - /* If sdp->detaching, then the refcount may already be 0, in >> + else if (SG_IS_DETACHING(sdp)) { >> + /* If detaching, then the refcount may already be 0, in >> * which case it would be a bug to do kref_get(). >> */ >> sdp = ERR_PTR(-ENODEV); >> @@ -2530,8 +2532,7 @@ sg_proc_seq_show_dev(struct seq_file *s, void *v) >> >> read_lock_irqsave(&sg_index_lock, iflags); >> sdp = it ? sg_lookup_dev(it->index) : NULL; >> - if ((NULL == sdp) || (NULL == sdp->device) || >> - (atomic_read(&sdp->detaching))) >> + if (!sdp || !sdp->device || SG_IS_DETACHING(sdp)) >> seq_puts(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n"); >> else { >> scsidp = sdp->device; >> @@ -2558,7 +2559,7 @@ sg_proc_seq_show_devstrs(struct seq_file *s, void *v) >> read_lock_irqsave(&sg_index_lock, iflags); >> sdp = it ? sg_lookup_dev(it->index) : NULL; >> scsidp = sdp ? sdp->device : NULL; >> - if (sdp && scsidp && (!atomic_read(&sdp->detaching))) >> + if (sdp && scsidp && !SG_IS_DETACHING(sdp)) >> seq_printf(s, "%8.8s\t%16.16s\t%4.4s\n", >> scsidp->vendor, scsidp->model, scsidp->rev); >> else >> @@ -2650,7 +2651,7 @@ sg_proc_seq_show_debug(struct seq_file *s, void *v) >> read_lock(&sdp->sfd_lock); >> if (!list_empty(&sdp->sfds)) { >> seq_printf(s, " >>> device=%s ", sdp->disk->disk_name); >> - if (atomic_read(&sdp->detaching)) >> + if (SG_IS_DETACHING(sdp)) >> seq_puts(s, "detaching pending close "); >> else if (sdp->device) { >> struct scsi_device *scsidp = sdp->device; >> @@ -2662,7 +2663,8 @@ sg_proc_seq_show_debug(struct seq_file *s, void *v) >> scsidp->host->hostt->emulated); >> } >> seq_printf(s, " sg_tablesize=%d excl=%d open_cnt=%d\n", >> - sdp->sg_tablesize, sdp->exclude, sdp->open_cnt); >> + sdp->sg_tablesize, SG_HAVE_EXCLUDE(sdp), >> + sdp->open_cnt); >> sg_proc_debug_helper(s, sdp); >> } >> read_unlock(&sdp->sfd_lock); >> > One thing to keep in mind here is that 'set_bit()' is not atomic; it > needs to be followed by a memory barrier or being replaced by > test_and_set_bit() if possible. > Please audit the code if that poses a problem. Hi, set_bit() and friends are documented in Documentation/atomic_bitops.txt so it would be surprising if they were not _atomic_ . There are variants documented in that file that _maybe_ non-atomic, they are the one that start with __ such as __set_bit(). So what I believe Documentation/atomic_bitops.txt is trying to say (in a sloppy kind of way) is that set_bit() and clear_bit() have _relaxed_ memory order. C/C++ standards (from 2011 onwards) have 6 memory orders: - relaxed [no memory order guarantees] - consume [C++17 says "please don't use"!] - acquire - release - acquire-release - sequentially consistent ["cst"] That list is from weakest to strongest. C/C++ default everything they can to "cst" as it requires the least thinking and is therefore the safest, but has the highest runtime overhead (depending somewhat on the platform). Linux adds a few wrinkles to the above as C/C++ are only considering threads while Linux additionally has ISRs, DMA, memory-mapped IO and the like to consider. From what I have read in the Documentation directories, most descriptions are written by gifted and un-gifted amateurs, apart from one amazing exception: Documentation/memory-barriers.txt . Now they are professions and the authors put their names, in full, at the top which IMO is always a good sign. Back to the review at hand, if set_bit() has relaxed memory order and needs to be seen by another thread (or ISR/bottom half) then it is relying on a following atomic operation that has stronger memory ordering guarantees (than relaxed). In my code I tend to use __set_bit() and __clear_bit() when a file descriptor or request object is being created, as no other thread should know of its existence at that time. Doug Gilbert Reference: C++ Concurrency in action, Second edition, Anthony Williams [As the C11 and C++11 concurrency subcommittees were "manned" by the same folks, they tried to make their memory models as compatible as possible.]
On 10/21/19 3:22 PM, Douglas Gilbert wrote: > On 2019-10-18 6:05 a.m., Hannes Reinecke wrote: [ .. ] >> One thing to keep in mind here is that 'set_bit()' is not atomic; it >> needs to be followed by a memory barrier or being replaced by >> test_and_set_bit() if possible. >> Please audit the code if that poses a problem. > > Hi, > set_bit() and friends are documented in Documentation/atomic_bitops.txt > so it would be surprising if they were not _atomic_ . There are variants > documented in that file that _maybe_ non-atomic, they are the one that > start with __ such as __set_bit(). > > So what I believe Documentation/atomic_bitops.txt is trying to say (in > a sloppy kind of way) is that set_bit() and clear_bit() have _relaxed_ > memory order. C/C++ standards (from 2011 onwards) have 6 memory orders: > - relaxed [no memory order guarantees] > - consume [C++17 says "please don't use"!] > - acquire > - release > - acquire-release > - sequentially consistent ["cst"] > > That list is from weakest to strongest. C/C++ default everything they > can to "cst" as it requires the least thinking and is therefore the > safest, but has the highest runtime overhead (depending somewhat on > the platform). > > Linux adds a few wrinkles to the above as C/C++ are only considering > threads while Linux additionally has ISRs, DMA, memory-mapped IO and > the like to consider. > > From what I have read in the Documentation directories, most > descriptions are written by gifted and un-gifted amateurs, apart from > one amazing exception: Documentation/memory-barriers.txt . Now they > are professions and the authors put their names, in full, at the > top which IMO is always a good sign. > > > Back to the review at hand, if set_bit() has relaxed memory order > and needs to be seen by another thread (or ISR/bottom half) then it > is relying on a following atomic operation that has stronger memory > ordering guarantees (than relaxed). In my code I tend to use > __set_bit() and __clear_bit() when a file descriptor or request object > is being created, as no other thread should know of its existence at > that time. > > Doug Gilbert > > Reference: C++ Concurrency in action, Second edition, Anthony Williams > [As the C11 and C++11 concurrency subcommittees were "manned" by the > same folks, they tried to make their memory models as compatible as > possible.] > > That's all I wanted to know. Thanks for the confirmation. Reviewed-by: Hannes Reinecke <hare@suse.com> Cheers, Hannes
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 9aa1b1030033..97ce84f0c51b 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -74,6 +74,11 @@ static char *sg_version_date = "20190606"; #define SG_DEFAULT_TIMEOUT mult_frac(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ) +/* Bit positions (flags) for sg_device::fdev_bm bitmask follow */ +#define SG_FDEV_EXCLUDE 0 /* have fd open with O_EXCL */ +#define SG_FDEV_DETACHING 1 /* may be unexpected device removal */ +#define SG_FDEV_LOG_SENSE 2 /* set by ioctl(SG_SET_DEBUG) */ + int sg_big_buff = SG_DEF_RESERVED_SIZE; /* N.B. This variable is readable and writeable via /proc/scsi/sg/def_reserved_size . Each time sg_open() is called a buffer @@ -155,14 +160,12 @@ struct sg_device { /* holds the state of each scsi generic device */ struct scsi_device *device; wait_queue_head_t open_wait; /* queue open() when O_EXCL present */ struct mutex open_rel_lock; /* held when in open() or release() */ - int sg_tablesize; /* adapter's max scatter-gather table size */ - u32 index; /* device index number */ struct list_head sfds; rwlock_t sfd_lock; /* protect access to sfd list */ - atomic_t detaching; /* 0->device usable, 1->device detaching */ - bool exclude; /* 1->open(O_EXCL) succeeded and is active */ + int sg_tablesize; /* adapter's max scatter-gather table size */ + u32 index; /* device index number */ int open_cnt; /* count of opens (perhaps < num(sfds) ) */ - char sgdebug; /* 0->off, 1->sense, 9->dump dev, 10-> all devs */ + unsigned long fdev_bm[1]; /* see SG_FDEV_* defines above */ struct gendisk *disk; struct cdev * cdev; /* char_dev [sysfs: /sys/cdev/major/sg<n>] */ struct kref d_ref; @@ -200,6 +203,9 @@ static void sg_device_destroy(struct kref *kref); #define SZ_SG_IO_HDR ((int)sizeof(struct sg_io_hdr)) /* v3 header */ #define SZ_SG_REQ_INFO ((int)sizeof(struct sg_req_info)) +#define SG_IS_DETACHING(sdp) test_bit(SG_FDEV_DETACHING, (sdp)->fdev_bm) +#define SG_HAVE_EXCLUDE(sdp) test_bit(SG_FDEV_EXCLUDE, (sdp)->fdev_bm) + /* * Kernel needs to be built with CONFIG_SCSI_LOGGING to see log messages. * 'depth' is a number between 1 (most severe) and 7 (most noisy, most @@ -273,26 +279,26 @@ sg_wait_open_event(struct sg_device *sdp, bool o_excl) while (sdp->open_cnt > 0) { mutex_unlock(&sdp->open_rel_lock); retval = wait_event_interruptible(sdp->open_wait, - (atomic_read(&sdp->detaching) || + (SG_IS_DETACHING(sdp) || !sdp->open_cnt)); mutex_lock(&sdp->open_rel_lock); if (retval) /* -ERESTARTSYS */ return retval; - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; } } else { - while (sdp->exclude) { + while (SG_HAVE_EXCLUDE(sdp)) { mutex_unlock(&sdp->open_rel_lock); retval = wait_event_interruptible(sdp->open_wait, - (atomic_read(&sdp->detaching) || - !sdp->exclude)); + (SG_IS_DETACHING(sdp) || + !SG_HAVE_EXCLUDE(sdp))); mutex_lock(&sdp->open_rel_lock); if (retval) /* -ERESTARTSYS */ return retval; - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; } } @@ -354,7 +360,7 @@ sg_open(struct inode *inode, struct file *filp) goto error_mutex_locked; } } else { - if (sdp->exclude) { + if (SG_HAVE_EXCLUDE(sdp)) { retval = -EBUSY; goto error_mutex_locked; } @@ -367,10 +373,10 @@ sg_open(struct inode *inode, struct file *filp) /* N.B. at this point we are holding the open_rel_lock */ if (o_excl) - sdp->exclude = true; + set_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm); if (sdp->open_cnt < 1) { /* no existing opens */ - sdp->sgdebug = 0; + clear_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm); q = sdp->device->request_queue; sdp->sg_tablesize = queue_max_segments(q); } @@ -393,8 +399,8 @@ sg_open(struct inode *inode, struct file *filp) return retval; out_undo: - if (o_excl) { - sdp->exclude = false; /* undo if error */ + if (o_excl) { /* undo if error */ + clear_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm); wake_up_interruptible(&sdp->open_wait); } error_mutex_locked: @@ -428,12 +434,10 @@ sg_release(struct inode *inode, struct file *filp) /* possibly many open()s waiting on exlude clearing, start many; * only open(O_EXCL)s wait on 0==open_cnt so only start one */ - if (sdp->exclude) { - sdp->exclude = false; + if (test_and_clear_bit(SG_FDEV_EXCLUDE, sdp->fdev_bm)) wake_up_interruptible_all(&sdp->open_wait); - } else if (0 == sdp->open_cnt) { + else if (sdp->open_cnt == 0) wake_up_interruptible(&sdp->open_wait); - } mutex_unlock(&sdp->open_rel_lock); return 0; } @@ -467,7 +471,7 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos) SG_LOG(3, sfp, "%s: write(3rd arg) count=%d\n", __func__, (int)count); if (!sdp) return -ENXIO; - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; if (!((filp->f_flags & O_NONBLOCK) || scsi_block_when_processing_errors(sdp->device))) @@ -666,7 +670,7 @@ sg_common_write(struct sg_fd *sfp, struct sg_request *srp, sg_remove_request(sfp, srp); return k; /* probably out of space --> ENOMEM */ } - if (atomic_read(&sdp->detaching)) { + if (SG_IS_DETACHING(sdp)) { if (srp->bio) { scsi_req_free_cmd(scsi_req(srp->rq)); blk_put_request(srp->rq); @@ -831,7 +835,7 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) } srp = sg_get_rq_mark(sfp, req_pack_id); if (!srp) { /* now wait on packet to arrive */ - if (atomic_read(&sdp->detaching)) { + if (SG_IS_DETACHING(sdp)) { retval = -ENODEV; goto free_old_hdr; } @@ -840,9 +844,9 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) goto free_old_hdr; } retval = wait_event_interruptible(sfp->read_wait, - (atomic_read(&sdp->detaching) || + (SG_IS_DETACHING(sdp) || (srp = sg_get_rq_mark(sfp, req_pack_id)))); - if (atomic_read(&sdp->detaching)) { + if (SG_IS_DETACHING(sdp)) { retval = -ENODEV; goto free_old_hdr; } @@ -997,7 +1001,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) switch (cmd_in) { case SG_IO: - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; if (!scsi_block_when_processing_errors(sdp->device)) return -ENXIO; @@ -1008,8 +1012,8 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) if (result < 0) return result; result = wait_event_interruptible(sfp->read_wait, - (srp_done(sfp, srp) || atomic_read(&sdp->detaching))); - if (atomic_read(&sdp->detaching)) + (srp_done(sfp, srp) || SG_IS_DETACHING(sdp))); + if (SG_IS_DETACHING(sdp)) return -ENODEV; write_lock_irq(&sfp->rq_list_lock); if (srp->done) { @@ -1052,7 +1056,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) else { sg_scsi_id_t __user *sg_idp = p; - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; __put_user((int) sdp->device->host->host_no, &sg_idp->host_no); @@ -1176,18 +1180,18 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) return result; } case SG_EMULATED_HOST: - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; return put_user(sdp->device->host->hostt->emulated, ip); case SCSI_IOCTL_SEND_COMMAND: - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; return sg_scsi_ioctl(sdp->device->request_queue, NULL, filp->f_mode, p); case SG_SET_DEBUG: result = get_user(val, ip); if (result) return result; - sdp->sgdebug = (char) val; + assign_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm, val); return 0; case BLKSECTGET: return put_user(max_sectors_bytes(sdp->device->request_queue), @@ -1208,7 +1212,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) case SCSI_IOCTL_PROBE_HOST: case SG_GET_TRANSFORM: case SG_SCSI_RESET: - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) return -ENODEV; break; default: @@ -1271,7 +1275,7 @@ sg_poll(struct file *filp, poll_table * wait) } read_unlock_irqrestore(&sfp->rq_list_lock, iflags); - if (sfp->parentdp && atomic_read(&sfp->parentdp->detaching)) { + if (sfp->parentdp && SG_IS_DETACHING(sfp->parentdp)) { p_res |= EPOLLHUP; } else if (!sfp->cmd_q) { if (count == 0) @@ -1419,7 +1423,7 @@ sg_rq_end_io(struct request *rq, blk_status_t status) return; sdp = sfp->parentdp; - if (unlikely(atomic_read(&sdp->detaching))) + if (unlikely(SG_IS_DETACHING(sdp))) pr_info("%s: device detaching\n", __func__); sense = req->sense; @@ -1440,9 +1444,9 @@ sg_rq_end_io(struct request *rq, blk_status_t status) srp->header.msg_status = msg_byte(result); srp->header.host_status = host_byte(result); srp->header.driver_status = driver_byte(result); - if ((sdp->sgdebug > 0) && - ((CHECK_CONDITION == srp->header.masked_status) || - (COMMAND_TERMINATED == srp->header.masked_status))) + if (test_bit(SG_FDEV_LOG_SENSE, sdp->fdev_bm) && + (srp->header.masked_status == CHECK_CONDITION || + srp->header.masked_status == COMMAND_TERMINATED)) __scsi_print_sense(sdp->device, __func__, sense, SCSI_SENSE_BUFFERSIZE); @@ -1557,7 +1561,7 @@ sg_alloc(struct gendisk *disk, struct scsi_device *scsidp) mutex_init(&sdp->open_rel_lock); INIT_LIST_HEAD(&sdp->sfds); init_waitqueue_head(&sdp->open_wait); - atomic_set(&sdp->detaching, 0); + clear_bit(SG_FDEV_DETACHING, sdp->fdev_bm); rwlock_init(&sdp->sfd_lock); sdp->sg_tablesize = queue_max_segments(q); sdp->index = k; @@ -1682,13 +1686,11 @@ sg_remove_device(struct device *cl_dev, struct class_interface *cl_intf) struct sg_device *sdp = dev_get_drvdata(cl_dev); unsigned long iflags; struct sg_fd *sfp; - int val; if (!sdp) return; - /* want sdp->detaching non-zero as soon as possible */ - val = atomic_inc_return(&sdp->detaching); - if (val > 1) + /* set this flag as soon as possible as it could be a surprise */ + if (test_and_set_bit(SG_FDEV_DETACHING, sdp->fdev_bm)) return; /* only want to do following once per device */ SCSI_LOG_TIMEOUT(3, sdev_printk(KERN_INFO, sdp->device, @@ -2218,7 +2220,7 @@ sg_add_sfp(struct sg_device *sdp) sfp->keep_orphan = SG_DEF_KEEP_ORPHAN; sfp->parentdp = sdp; write_lock_irqsave(&sdp->sfd_lock, iflags); - if (atomic_read(&sdp->detaching)) { + if (SG_IS_DETACHING(sdp)) { write_unlock_irqrestore(&sdp->sfd_lock, iflags); kfree(sfp); return ERR_PTR(-ENODEV); @@ -2315,8 +2317,8 @@ sg_get_dev(int dev) sdp = sg_lookup_dev(dev); if (!sdp) sdp = ERR_PTR(-ENXIO); - else if (atomic_read(&sdp->detaching)) { - /* If sdp->detaching, then the refcount may already be 0, in + else if (SG_IS_DETACHING(sdp)) { + /* If detaching, then the refcount may already be 0, in * which case it would be a bug to do kref_get(). */ sdp = ERR_PTR(-ENODEV); @@ -2530,8 +2532,7 @@ sg_proc_seq_show_dev(struct seq_file *s, void *v) read_lock_irqsave(&sg_index_lock, iflags); sdp = it ? sg_lookup_dev(it->index) : NULL; - if ((NULL == sdp) || (NULL == sdp->device) || - (atomic_read(&sdp->detaching))) + if (!sdp || !sdp->device || SG_IS_DETACHING(sdp)) seq_puts(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n"); else { scsidp = sdp->device; @@ -2558,7 +2559,7 @@ sg_proc_seq_show_devstrs(struct seq_file *s, void *v) read_lock_irqsave(&sg_index_lock, iflags); sdp = it ? sg_lookup_dev(it->index) : NULL; scsidp = sdp ? sdp->device : NULL; - if (sdp && scsidp && (!atomic_read(&sdp->detaching))) + if (sdp && scsidp && !SG_IS_DETACHING(sdp)) seq_printf(s, "%8.8s\t%16.16s\t%4.4s\n", scsidp->vendor, scsidp->model, scsidp->rev); else @@ -2650,7 +2651,7 @@ sg_proc_seq_show_debug(struct seq_file *s, void *v) read_lock(&sdp->sfd_lock); if (!list_empty(&sdp->sfds)) { seq_printf(s, " >>> device=%s ", sdp->disk->disk_name); - if (atomic_read(&sdp->detaching)) + if (SG_IS_DETACHING(sdp)) seq_puts(s, "detaching pending close "); else if (sdp->device) { struct scsi_device *scsidp = sdp->device; @@ -2662,7 +2663,8 @@ sg_proc_seq_show_debug(struct seq_file *s, void *v) scsidp->host->hostt->emulated); } seq_printf(s, " sg_tablesize=%d excl=%d open_cnt=%d\n", - sdp->sg_tablesize, sdp->exclude, sdp->open_cnt); + sdp->sg_tablesize, SG_HAVE_EXCLUDE(sdp), + sdp->open_cnt); sg_proc_debug_helper(s, sdp); } read_unlock(&sdp->sfd_lock);
Introduce bitops in sg_device to replace an atomic, a bool and a char. That char (sgdebug) had been reduced to only two states. Add some associated macros to make the code a little clearer. Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> --- drivers/scsi/sg.c | 104 +++++++++++++++++++++++----------------------- 1 file changed, 53 insertions(+), 51 deletions(-)