floppy: use atomic type for usage_count

The usage_count was being protected by a lock which was only there to
create an atomic counter.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 12 insertions, 30 deletions

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 5816387f9bce..9b4746871227 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -578,7 +578,7 @@ static void reset_fdc(void);
 #define NEED_1_RECAL    -2
 #define NEED_2_RECAL    -3
 
-static int usage_count;
+static atomic_t usage_count = ATOMIC_INIT(0);
 
 /* buffer related variables */
 static int buffer_track = -1;
@@ -860,7 +860,7 @@ static void set_fdc(int drive)
 /* locks the driver */
 static int _lock_fdc(int drive, bool interruptible, int line)
 {
-        if (!usage_count) {
+        if (atomic_read(&usage_count) == 0) {
                 pr_err("Trying to lock fdc while usage count=0 at line %d\n",
                        line);
                 return -1;
@@ -2941,7 +2941,7 @@ static void do_fd_request(struct request_queue *q)
                 return;
         }
 
-        if (usage_count == 0) {
+        if (atomic_read(&usage_count) == 0) {
                 pr_info("warning: usage count=0, current_req=%p exiting\n",
                         current_req);
                 pr_info("sect=%ld type=%x flags=%x\n",
@@ -3858,7 +3858,7 @@ static int floppy_revalidate(struct gendisk *disk)
         if (test_bit(FD_DISK_CHANGED_BIT, &UDRS->flags) ||
             test_bit(FD_VERIFY_BIT, &UDRS->flags) ||
             test_bit(drive, &fake_change) || NO_GEOM) {
-                if (usage_count == 0) {
+                if (atomic_read(&usage_count) == 0) {
                         pr_info("VFS: revalidate called on non-open device.\n");
                         return -EFAULT;
                 }
@@ -4357,7 +4357,7 @@ out_unreg_platform_dev:
         platform_device_unregister(&floppy_device[drive]);
 out_flush_work:
         flush_scheduled_work();
-        if (usage_count)
+        if (atomic_read(&usage_count))
                 floppy_release_irq_and_dma();
 out_unreg_region:
         blk_unregister_region(MKDEV(FLOPPY_MAJOR, 0), 256);
@@ -4374,8 +4374,6 @@ out_put_disk:
         return err;
 }
 
-static DEFINE_SPINLOCK(floppy_usage_lock);
-
 static const struct io_region {
         int offset;
         int size;
@@ -4421,14 +4419,8 @@ static void floppy_release_regions(int fdc)
 
 static int floppy_grab_irq_and_dma(void)
 {
-        unsigned long flags;
-
-        spin_lock_irqsave(&floppy_usage_lock, flags);
-        if (usage_count++) {
-                spin_unlock_irqrestore(&floppy_usage_lock, flags);
+        if (atomic_inc_return(&usage_count) > 1)
                 return 0;
-        }
-        spin_unlock_irqrestore(&floppy_usage_lock, flags);
 
         /*
          * We might have scheduled a free_irq(), wait it to
@@ -4439,9 +4431,7 @@ static int floppy_grab_irq_and_dma(void)
         if (fd_request_irq()) {
                 DPRINT("Unable to grab IRQ%d for the floppy driver\n",
                        FLOPPY_IRQ);
-                spin_lock_irqsave(&floppy_usage_lock, flags);
-                usage_count--;
-                spin_unlock_irqrestore(&floppy_usage_lock, flags);
+                atomic_dec(&usage_count);
                 return -1;
         }
         if (fd_request_dma()) {
@@ -4451,9 +4441,7 @@ static int floppy_grab_irq_and_dma(void)
                         use_virtual_dma = can_use_virtual_dma = 1;
                 if (!(can_use_virtual_dma & 1)) {
                         fd_free_irq();
-                        spin_lock_irqsave(&floppy_usage_lock, flags);
-                        usage_count--;
-                        spin_unlock_irqrestore(&floppy_usage_lock, flags);
+                        atomic_dec(&usage_count);
                         return -1;
                 }
         }
@@ -4488,9 +4476,7 @@ cleanup:
         fd_free_dma();
         while (--fdc >= 0)
                 floppy_release_regions(fdc);
-        spin_lock_irqsave(&floppy_usage_lock, flags);
-        usage_count--;
-        spin_unlock_irqrestore(&floppy_usage_lock, flags);
+        atomic_dec(&usage_count);
         return -1;
 }
 
@@ -4502,14 +4488,10 @@ static void floppy_release_irq_and_dma(void)
 #endif
         long tmpsize;
         unsigned long tmpaddr;
-        unsigned long flags;
 
-        spin_lock_irqsave(&floppy_usage_lock, flags);
-        if (--usage_count) {
-                spin_unlock_irqrestore(&floppy_usage_lock, flags);
+        if (!atomic_dec_and_test(&usage_count))
                 return;
-        }
-        spin_unlock_irqrestore(&floppy_usage_lock, flags);
+
         if (irqdma_allocated) {
                 fd_disable_dma();
                 fd_free_dma();
@@ -4602,7 +4584,7 @@ static void __exit floppy_module_exit(void)
         del_timer_sync(&fd_timer);
         blk_cleanup_queue(floppy_queue);
 
-        if (usage_count)
+        if (atomic_read(&usage_count))
                 floppy_release_irq_and_dma();
 
         /* eject disk, if any */