Btrfs: cleanup pages properly when ENOMEM in compression

We were freeing non-existent pages which was causing a panic for a user who
was suffering from ENOMEM.  This patch fixes the problem.  Thanks,

Reported-by: Jérôme Poulin <jeromepoulin@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 43d1c5a..c6467aa 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -577,6 +577,7 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
        u64 em_start;
        struct extent_map *em;
        int ret = -ENOMEM;
+       int faili = 0;
        u32 *sums;
 
        tree = &BTRFS_I(inode)->io_tree;
@@ -626,9 +627,13 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
        for (pg_index = 0; pg_index < nr_pages; pg_index++) {
                cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
                                                              __GFP_HIGHMEM);
-               if (!cb->compressed_pages[pg_index])
+               if (!cb->compressed_pages[pg_index]) {
+                       faili = pg_index - 1;
+                       ret = -ENOMEM;
                        goto fail2;
+               }
        }
+       faili = nr_pages - 1;
        cb->nr_pages = nr_pages;
 
        add_ra_bio_pages(inode, em_start + em_len, cb);
@@ -713,8 +718,10 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
        return 0;
 
 fail2:
-       for (pg_index = 0; pg_index < nr_pages; pg_index++)
-               free_page((unsigned long)cb->compressed_pages[pg_index]);
+       while (faili >= 0) {
+               __free_page(cb->compressed_pages[faili]);
+               faili--;
+       }
 
        kfree(cb->compressed_pages);
 fail1: