Btrfs: make sure we don't overflow the free space cache crc page

The free space cache uses only one page for crcs right now,
which means we can't have a cache file bigger than the
crcs we can fit in the first page.  This adds a check to
enforce that restriction.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index dd38d4c3a5994a78082453cb0aee6ff82f7e0ab4..1cb72394498cff80add47a44250d6ae68bee5852 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -590,10 +590,25 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
 
        num_pages = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >>
                PAGE_CACHE_SHIFT;
+
+       /* Since the first page has all of our checksums and our generation we
+        * need to calculate the offset into the page that we can start writing
+        * our entries.
+        */
+       first_page_offset = (sizeof(u32) * num_pages) + sizeof(u64);
+
        filemap_write_and_wait(inode->i_mapping);
        btrfs_wait_ordered_range(inode, inode->i_size &
                                 ~(root->sectorsize - 1), (u64)-1);
 
+       /* make sure we don't overflow that first page */
+       if (first_page_offset + sizeof(struct btrfs_free_space_entry) >= PAGE_CACHE_SIZE) {
+               /* this is really the same as running out of space, where we also return 0 */
+               printk(KERN_CRIT "Btrfs: free space cache was too big for the crc page\n");
+               ret = 0;
+               goto out_update;
+       }
+
        /* We need a checksum per page. */
        crc = checksums = kzalloc(sizeof(u32) * num_pages, GFP_NOFS);
        if (!crc)
@@ -605,12 +620,6 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
                return -1;
        }
 
-       /* Since the first page has all of our checksums and our generation we
-        * need to calculate the offset into the page that we can start writing
-        * our entries.
-        */
-       first_page_offset = (sizeof(u32) * num_pages) + sizeof(u64);
-
        /* Get the cluster for this block_group if it exists */
        if (block_group && !list_empty(&block_group->cluster_list))
                cluster = list_entry(block_group->cluster_list.next,
@@ -872,12 +881,14 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
        ret = 1;
 
 out_free:
+       kfree(checksums);
+       kfree(pages);
+
+out_update:
        if (ret != 1) {
                invalidate_inode_pages2_range(inode->i_mapping, 0, index);
                BTRFS_I(inode)->generation = 0;
        }
-       kfree(checksums);
-       kfree(pages);
        btrfs_update_inode(trans, root, inode);
        return ret;
 }