[LogFS] Prevent memory corruption on large deletes

Removing sufficiently large files would create aliases for a large
number of segments.  This in turn results in a large number of journal
entries and an overflow of s_je_array.

Cheap fix is to add a BUG_ON, turning memory corruption into something
annoying, but less dangerous.  Real fix is to count the number of
affected segments and prevent the problem completely.

Signed-off-by: Joern Engel <joern@logfs.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c
index 3659c37fbd72..7e0c39c49719 100644
--- a/fs/logfs/readwrite.c
+++ b/fs/logfs/readwrite.c
@@ -1219,6 +1219,18 @@ static void free_shadow(struct inode *inode, struct logfs_shadow *shadow)
         mempool_free(shadow, super->s_shadow_pool);
 }
 
+static void mark_segment(struct shadow_tree *tree, u32 segno)
+{
+        int err;
+
+        if (!btree_lookup32(&tree->segment_map, segno)) {
+                err = btree_insert32(&tree->segment_map, segno, (void *)1,
+                                GFP_NOFS);
+                BUG_ON(err);
+                tree->no_shadowed_segments++;
+        }
+}
+
 /**
  * fill_shadow_tree - Propagate shadow tree changes due to a write
  * @inode:      Inode owning the page
@@ -1266,6 +1278,8 @@ static void fill_shadow_tree(struct inode *inode, struct page *page,
 
                 super->s_dirty_used_bytes += shadow->new_len;
                 super->s_dirty_free_bytes += shadow->old_len;
+                mark_segment(tree, shadow->old_ofs >> super->s_segshift);
+                mark_segment(tree, shadow->new_ofs >> super->s_segshift);
         }
 }