btrfs: fix defrag 32-bit integer overflow

When defragging a very large file, the cluster variable can wrap its 32-bit
signed int type and become negative, which eventually gets passed to
btrfs_force_ra() as a very large unsigned long value.  On 32-bit platforms,
this eventually results in an Oops from the SLAB allocator.

Change the cluster and max_cluster signed int variables to unsigned long to
match the readahead functions.  This also allows the min() comparison in
btrfs_defrag_file() to work as intended.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 62c62b4fa55b..34772cbcc7aa 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1036,7 +1036,7 @@ out:
 static int cluster_pages_for_defrag(struct inode *inode,
                                     struct page **pages,
                                     unsigned long start_index,
-                                    int num_pages)
+                                    unsigned long num_pages)
 {
         unsigned long file_end;
         u64 isize = i_size_read(inode);
@@ -1194,8 +1194,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
         int defrag_count = 0;
         int compress_type = BTRFS_COMPRESS_ZLIB;
         int extent_thresh = range->extent_thresh;
-        int max_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT;
-        int cluster = max_cluster;
+        unsigned long max_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT;
+        unsigned long cluster = max_cluster;
         u64 new_align = ~((u64)128 * 1024 - 1);
         struct page **pages = NULL;