1 files changed, 37 insertions, 15 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6d1b93c8aafb..021694c08181 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2166,16 +2166,23 @@ static noinline int record_one_backref(u64 inum, u64 offset, u64 root_id,
                 if (btrfs_file_extent_disk_bytenr(leaf, extent) != old->bytenr)
                         continue;
 
-                extent_offset = btrfs_file_extent_offset(leaf, extent);
-                if (key.offset - extent_offset != offset)
+                /*
+                 * 'offset' refers to the exact key.offset,
+                 * NOT the 'offset' field in btrfs_extent_data_ref, ie.
+                 * (key.offset - extent_offset).
+                 */
+                if (key.offset != offset)
                         continue;
 
+                extent_offset = btrfs_file_extent_offset(leaf, extent);
                 num_bytes = btrfs_file_extent_num_bytes(leaf, extent);
+
                 if (extent_offset >= old->extent_offset + old->offset +
                     old->len || extent_offset + num_bytes <=
                     old->extent_offset + old->offset)
                         continue;
 
+                ret = 0;
                 break;
         }
 
@@ -2187,7 +2194,7 @@ static noinline int record_one_backref(u64 inum, u64 offset, u64 root_id,
 
         backref->root_id = root_id;
         backref->inum = inum;
-        backref->file_pos = offset + extent_offset;
+        backref->file_pos = offset;
         backref->num_bytes = num_bytes;
         backref->extent_offset = extent_offset;
         backref->generation = btrfs_file_extent_generation(leaf, extent);
@@ -2210,7 +2217,8 @@ static noinline bool record_extent_backrefs(struct btrfs_path *path,
         new->path = path;
 
         list_for_each_entry_safe(old, tmp, &new->head, list) {
-                ret = iterate_inodes_from_logical(old->bytenr, fs_info,
+                ret = iterate_inodes_from_logical(old->bytenr +
+                                                  old->extent_offset, fs_info,
                                                   path, record_one_backref,
                                                   old);
                 BUG_ON(ret < 0 && ret != -ENOENT);
@@ -4391,9 +4399,6 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
         int mask = attr->ia_valid;
         int ret;
 
-        if (newsize == oldsize)
-                return 0;
-
         /*
          * The regular truncate() case without ATTR_CTIME and ATTR_MTIME is a
          * special case where we need to update the times despite not having
@@ -5165,14 +5170,31 @@ next:
         }
 
         /* Reached end of directory/root. Bump pos past the last item. */
-        if (key_type == BTRFS_DIR_INDEX_KEY)
-                /*
-                 * 32-bit glibc will use getdents64, but then strtol -
-                 * so the last number we can serve is this.
-                 */
-                ctx->pos = 0x7fffffff;
-        else
-                ctx->pos++;
+        ctx->pos++;
+
+        /*
+         * Stop new entries from being returned after we return the last
+         * entry.
+         *
+         * New directory entries are assigned a strictly increasing
+         * offset.  This means that new entries created during readdir
+         * are *guaranteed* to be seen in the future by that readdir.
+         * This has broken buggy programs which operate on names as
+         * they're returned by readdir.  Until we re-use freed offsets
+         * we have this hack to stop new entries from being returned
+         * under the assumption that they'll never reach this huge
+         * offset.
+         *
+         * This is being careful not to overflow 32bit loff_t unless the
+         * last entry requires it because doing so has broken 32bit apps
+         * in the past.
+         */
+        if (key_type == BTRFS_DIR_INDEX_KEY) {
+                if (ctx->pos >= INT_MAX)
+                        ctx->pos = LLONG_MAX;
+                else
+                        ctx->pos = INT_MAX;
+        }
 nopos:
         ret = 0;
 err: