[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, 8 insertions, 0 deletions

diff --git a/fs/logfs/gc.c b/fs/logfs/gc.c
index 92949f95a901..e8253e7fb6b2 100644
--- a/fs/logfs/gc.c
+++ b/fs/logfs/gc.c
@@ -458,6 +458,14 @@ static void __logfs_gc_pass(struct super_block *sb, int target)
         struct logfs_block *block;
         int round, progress, last_progress = 0;
 
+        /*
+         * Doing too many changes to the segfile at once would result
+         * in a large number of aliases.  Write the journal before
+         * things get out of hand.
+         */
+        if (super->s_shadow_tree.no_shadowed_segments >= MAX_OBJ_ALIASES)
+                logfs_write_anchor(sb);
+
         if (no_free_segments(sb) >= target &&
                         super->s_no_object_aliases < MAX_OBJ_ALIASES)
                 return;