floppy: remove floppy-specific O_EXCL handling

Block layer now handles O_EXCL in a generic way for block devices.

The semantics is however different for floppy and all other block devices,
as floppy driver contains its own O_EXCL handling.

The semantics for all-but-floppy bdevs is "there can be at most one O_EXCL
open of this file", while for floppy bdev the semantics is "if someone has
the bdev open with O_EXCL, noone else can open it".

There is actual userspace-observable change in behavior because of this
since commit e525fd89d380c ("block: make blkdev_get/put() handle exclusive
access") -- on kernels containing this commit, mount of /dev/fd0 causes
the fd0 block device be claimed with _EXCL, preventing subsequent
open(/dev/fd0).

Bring things back into shape, i.e.  make it possible, analogically to
other block devices, to mount the floppy and open() it afterwards --
remove the floppy-specific handling and let the generic bdev code O_EXCL
handling take over.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 4 insertions, 14 deletions

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 48e1d70740d..cce7df367b7 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3607,9 +3607,7 @@ static int floppy_release(struct gendisk *disk, fmode_t mode)
 
         mutex_lock(&floppy_mutex);
         mutex_lock(&open_lock);
-        if (UDRS->fd_ref < 0)
-                UDRS->fd_ref = 0;
-        else if (!UDRS->fd_ref--) {
+        if (!UDRS->fd_ref--) {
                 DPRINT("floppy_release with fd_ref == 0");
                 UDRS->fd_ref = 0;
         }
@@ -3645,13 +3643,7 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
                 set_bit(FD_VERIFY_BIT, &UDRS->flags);
         }
 
-        if (UDRS->fd_ref == -1 || (UDRS->fd_ref && (mode & FMODE_EXCL)))
-                goto out2;
-
-        if (mode & FMODE_EXCL)
-                UDRS->fd_ref = -1;
-        else
-                UDRS->fd_ref++;
+        UDRS->fd_ref++;
 
         opened_bdev[drive] = bdev;
 
@@ -3714,10 +3706,8 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
         mutex_unlock(&floppy_mutex);
         return 0;
 out:
-        if (UDRS->fd_ref < 0)
-                UDRS->fd_ref = 0;
-        else
-                UDRS->fd_ref--;
+        UDRS->fd_ref--;
+
         if (!UDRS->fd_ref)
                 opened_bdev[drive] = NULL;
 out2: