2 files changed, 62 insertions, 30 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7346c96308a5..99d6af811747 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -706,8 +706,13 @@ retry:
  * @bdev is about to be opened exclusively.  Check @bdev can be opened
  * exclusively and mark that an exclusive open is in progress.  Each
  * successful call to this function must be matched with a call to
- * either bd_claim() or bd_abort_claiming().  If this function
- * succeeds, the matching bd_claim() is guaranteed to succeed.
+ * either bd_finish_claiming() or bd_abort_claiming() (which do not
+ * fail).
+ *
+ * This function is used to gain exclusive access to the block device
+ * without actually causing other exclusive open attempts to fail. It
+ * should be used when the open sequence itself requires exclusive
+ * access but may subsequently fail.
  *
  * CONTEXT:
  * Might sleep.
@@ -734,6 +739,7 @@ static struct block_device *bd_start_claiming(struct block_device *bdev,
                 return ERR_PTR(-ENXIO);
 
         whole = bdget_disk(disk, 0);
+        module_put(disk->fops->owner);
         put_disk(disk);
         if (!whole)
                 return ERR_PTR(-ENOMEM);
@@ -782,15 +788,46 @@ static void bd_abort_claiming(struct block_device *whole, void *holder)
         __bd_abort_claiming(whole, holder);             /* releases bdev_lock */
 }
 
+/* increment holders when we have a legitimate claim. requires bdev_lock */
+static void __bd_claim(struct block_device *bdev, struct block_device *whole,
+                                        void *holder)
+{
+        /* note that for a whole device bd_holders
+         * will be incremented twice, and bd_holder will
+         * be set to bd_claim before being set to holder
+         */
+        whole->bd_holders++;
+        whole->bd_holder = bd_claim;
+        bdev->bd_holders++;
+        bdev->bd_holder = holder;
+}
+
+/**
+ * bd_finish_claiming - finish claiming a block device
+ * @bdev: block device of interest (passed to bd_start_claiming())
+ * @whole: whole block device returned by bd_start_claiming()
+ * @holder: holder trying to claim @bdev
+ *
+ * Finish a claiming block started by bd_start_claiming().
+ *
+ * CONTEXT:
+ * Grabs and releases bdev_lock.
+ */
+static void bd_finish_claiming(struct block_device *bdev,
+                                struct block_device *whole, void *holder)
+{
+        spin_lock(&bdev_lock);
+        BUG_ON(!bd_may_claim(bdev, whole, holder));
+        __bd_claim(bdev, whole, holder);
+        __bd_abort_claiming(whole, holder); /* not actually an abort */
+}
+
 /**
  * bd_claim - claim a block device
  * @bdev: block device to claim
  * @holder: holder trying to claim @bdev
  *
- * Try to claim @bdev which must have been opened successfully.  This
- * function may be called with or without preceding
- * blk_start_claiming().  In the former case, this function is always
- * successful and terminates the claiming block.
+ * Try to claim @bdev which must have been opened successfully.
  *
  * CONTEXT:
  * Might sleep.
@@ -806,23 +843,10 @@ int bd_claim(struct block_device *bdev, void *holder)
         might_sleep();
 
         spin_lock(&bdev_lock);
-
         res = bd_prepare_to_claim(bdev, whole, holder);
-        if (res == 0) {
-                /* note that for a whole device bd_holders
-                 * will be incremented twice, and bd_holder will
-                 * be set to bd_claim before being set to holder
-                 */
-                whole->bd_holders++;
-                whole->bd_holder = bd_claim;
-                bdev->bd_holders++;
-                bdev->bd_holder = holder;
-        }
-
-        if (whole->bd_claiming)
-                __bd_abort_claiming(whole, holder);     /* releases bdev_lock */
-        else
-                spin_unlock(&bdev_lock);
+        if (res == 0)
+                __bd_claim(bdev, whole, holder);
+        spin_unlock(&bdev_lock);
 
         return res;
 }
@@ -1476,7 +1500,7 @@ static int blkdev_open(struct inode * inode, struct file * filp)
 
         if (whole) {
                 if (res == 0)
-                        BUG_ON(bd_claim(bdev, filp) != 0);
+                        bd_finish_claiming(bdev, whole, filp);
                 else
                         bd_abort_claiming(whole, filp);
         }
@@ -1712,7 +1736,7 @@ struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *h
         if ((mode & FMODE_WRITE) && bdev_read_only(bdev))
                 goto out_blkdev_put;
 
-        BUG_ON(bd_claim(bdev, holder) != 0);
+        bd_finish_claiming(bdev, whole, holder);
         return bdev;
 
 out_blkdev_put:
diff --git a/fs/pipe.c b/fs/pipe.c
index 69c4c7c13ea9..279eef96c51c 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1145,13 +1145,20 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
          * and adjust the indexes.
          */
         if (pipe->nrbufs) {
-                const unsigned int tail = pipe->nrbufs & (pipe->buffers - 1);
-                const unsigned int head = pipe->nrbufs - tail;
+                unsigned int tail;
+                unsigned int head;
 
+                tail = pipe->curbuf + pipe->nrbufs;
+                if (tail < pipe->buffers)
+                        tail = 0;
+                else
+                        tail &= (pipe->buffers - 1);
+
+                head = pipe->nrbufs - tail;
                 if (head)
                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
                 if (tail)
-                        memcpy(bufs + head, pipe->bufs + pipe->curbuf, tail * sizeof(struct pipe_buffer));
+                        memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
         }
 
         pipe->curbuf = 0;
@@ -1208,12 +1215,13 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
                 size = round_pipe_size(arg);
                 nr_pages = size >> PAGE_SHIFT;
 
+                ret = -EINVAL;
+                if (!nr_pages)
+                        goto out;
+
                 if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
                         ret = -EPERM;
                         goto out;
-                } else if (nr_pages < PAGE_SIZE) {
-                        ret = -EINVAL;
-                        goto out;
                 }
                 ret = pipe_set_size(pipe, nr_pages);
                 break;