On Sat, Mar 31, 2007 at 08:35:09AM -0400, Theodore Tso wrote:
> And we can't really check the case where a directory gets turned into
> a regular file without destroying e2fsck's performance, since that
> would require reading the first block of every single file, and this
> also significantly increases the chance of false positives.  So it's a
> lot of complexity for what seems to have always been an artificial
> test case.

OK, this is what I have done so far.  Not checked in yet, but it looks
right to me.  Note that this makes your testcase have a very booring
result.  :-)

I'm going to let this one soak for a bit to make sure we don't pick up
any fase positives or negatives in the hueristics.

                                                - Ted

diff -r 11d3e029aa83 e2fsck/message.c
--- a/e2fsck/message.c  Thu Mar 29 00:32:23 2007 -0400
+++ b/e2fsck/message.c  Sat Mar 31 10:36:55 2007 -0400
@@ -35,6 +35,7 @@
  *     %Id     <inode> -> i_dir_acl
  *     %Iu     <inode> -> i_uid
  *     %Ig     <inode> -> i_gid
+ *     %It     <inode type>
  *     %j      <ino2>                  inode number
  *     %m      <com_err error message>
  *     %N      <num>
@@ -310,6 +311,25 @@ static _INLINE_ void expand_inode_expres
                printf("%d", (inode->i_gid |
                              (inode->osd2.linux2.l_i_gid_high << 16)));
                break;
+       case 't':
+               if (LINUX_S_ISREG(inode->i_mode)) 
+                       printf(_("regular file"));
+               else if (LINUX_S_ISDIR(inode->i_mode)) 
+                       printf(_("directory"));
+               else if (LINUX_S_ISCHR(inode->i_mode)) 
+                       printf(_("character device"));
+               else if (LINUX_S_ISBLK(inode->i_mode)) 
+                       printf(_("block device"));
+               else if (LINUX_S_ISFIFO(inode->i_mode)) 
+                       printf(_("named pipe"));
+               else if (LINUX_S_ISLNK(inode->i_mode)) 
+                       printf(_("symbolic link"));
+               else if (LINUX_S_ISSOCK(inode->i_mode))
+                       printf(_("socket"));
+               else
+                       printf(_("unknown file type with mode 0%o"),
+                              inode->i_mode);
+               break;
        default:
        no_inode:
                printf("%%I%c", ch);
diff -r 11d3e029aa83 e2fsck/pass1.c
--- a/e2fsck/pass1.c    Thu Mar 29 00:32:23 2007 -0400
+++ b/e2fsck/pass1.c    Sat Mar 31 10:36:55 2007 -0400
@@ -133,11 +133,10 @@ int e2fsck_pass1_check_device_inode(ext2
        int     i;
 
        /*
-        * If i_blocks is non-zero, or the index flag is set, then
-        * this is a bogus device/fifo/socket
+        * If the index flag is set, then this is a bogus
+        * device/fifo/socket
         */
-       if ((ext2fs_inode_data_blocks(fs, inode) != 0) ||
-           (inode->i_flags & EXT2_INDEX_FL))
+       if (inode->i_flags & EXT2_INDEX_FL)
                return 0;
 
        /*
@@ -370,6 +369,73 @@ static void check_inode_extra_space(e2fs
        if (*eamagic == EXT2_EXT_ATTR_MAGIC) {
                /* it seems inode has an extended attribute(s) in body */
                check_ea_in_inode(ctx, pctx);
+       }
+}
+
+/* 
+ * Check to see if the inode might really be a directory, despite i_mode
+ *
+ * This is a lot of complexity for something for which I'm not really
+ * convinced happens frequently in the wild.  If for any reason this
+ * causes any problems, take this code out.
+ * [tytso:20070331.0827EDT]
+ */
+static void check_is_really_dir(e2fsck_t ctx, struct problem_context *pctx,
+                               char *buf)
+{
+       struct ext2_inode *inode = pctx->inode;
+       int i, not_device = 0;
+       blk_t blk;
+       struct ext2_dir_entry   *dirent;
+
+       if (LINUX_S_ISDIR(inode->i_mode) || LINUX_S_ISREG(inode->i_mode))
+               return;
+
+       for (i=0; i < EXT2_N_BLOCKS; i++) {
+               blk = inode->i_block[i];
+               if (!blk)
+                       continue;
+               if (i >= 4)
+                       not_device++;
+
+               if (blk < ctx->fs->super->s_first_data_block ||
+                   blk >= ctx->fs->super->s_blocks_count ||
+                   ext2fs_fast_test_block_bitmap(ctx->block_found_map, blk))
+                       return; /* Invalid block, can't be dir */
+       }
+
+       if ((LINUX_S_ISCHR(inode->i_mode) || LINUX_S_ISBLK(inode->i_mode)) && 
+           (inode->i_links_count == 1) && !not_device)
+               return;
+
+       if (LINUX_S_ISLNK(inode->i_mode) && inode->i_links_count == 1)
+               return;
+
+       if (ext2fs_read_dir_block(ctx->fs, inode->i_block[0], buf))
+               return;
+
+       dirent = (struct ext2_dir_entry *) buf;
+       if (((dirent->name_len & 0xFF) != 1) ||
+           (dirent->name[0] != '.') ||
+           (dirent->inode != pctx->ino) ||
+           (dirent->rec_len < 12) ||
+           (dirent->rec_len % 4) ||
+           (dirent->rec_len >= ctx->fs->blocksize - 12))
+               return;
+
+       dirent = (struct ext2_dir_entry *) (buf + dirent->rec_len);
+       if (((dirent->name_len & 0xFF) != 2) ||
+           (dirent->name[0] != '.') ||
+           (dirent->name[1] != '.') ||
+           (dirent->rec_len < 12) ||
+           (dirent->rec_len % 4))
+               return;
+
+       if (fix_problem(ctx, PR_1_TREAT_AS_DIRECTORY, pctx)) {
+               inode->i_mode = (inode->i_mode & 07777) | LINUX_S_IFDIR;
+               e2fsck_write_inode_full(ctx, pctx->ino, inode, 
+                                       EXT2_INODE_SIZE(ctx->fs->super), 
+                                       "check_is_really_dir");
        }
 }
 
@@ -770,6 +836,7 @@ void e2fsck_pass1(e2fsck_t ctx)
                }
 
                check_inode_extra_space(ctx, &pctx);
+               check_is_really_dir(ctx, &pctx, block_buf);
 
                if (LINUX_S_ISDIR(inode->i_mode)) {
                        ext2fs_mark_inode_bitmap(ctx->inode_dir_map, ino);
diff -r 11d3e029aa83 e2fsck/pass3.c
--- a/e2fsck/pass3.c    Thu Mar 29 00:32:23 2007 -0400
+++ b/e2fsck/pass3.c    Sat Mar 31 10:36:55 2007 -0400
@@ -645,6 +645,7 @@ static int fix_dotdot_proc(struct ext2_d
                fix_problem(fp->ctx, PR_3_ADJUST_INODE, &pctx);
        }
        dirent->inode = fp->parent;
+       dirent->name_len = (dirent->name_len & 0xFF) | EXT2_FT_DIR << 8;
 
        fp->done++;
        return DIRENT_ABORT | DIRENT_CHANGED;
diff -r 11d3e029aa83 e2fsck/problem.c
--- a/e2fsck/problem.c  Thu Mar 29 00:32:23 2007 -0400
+++ b/e2fsck/problem.c  Sat Mar 31 10:36:55 2007 -0400
@@ -778,6 +778,11 @@ static struct e2fsck_problem problem_tab
        { PR_1_ATTR_HASH,
          N_("@a in @i %i has a hash (%N) which is @n (must be 0)\n"),
          PROMPT_CLEAR, PR_PREEN_OK },
+
+       /* inode appears to be a directory */
+       { PR_1_TREAT_AS_DIRECTORY,
+         N_("@i %i is a %It but it looks like it is really a directory\n"),
+         PROMPT_FIX, PR_PREEN_OK },
 
        /* Pass 1b errors */
 
diff -r 11d3e029aa83 e2fsck/problem.h
--- a/e2fsck/problem.h  Thu Mar 29 00:32:23 2007 -0400
+++ b/e2fsck/problem.h  Sat Mar 31 10:36:55 2007 -0400
@@ -452,6 +452,9 @@ struct problem_context {
 /* wrong EA hash value */
 #define PR_1_ATTR_HASH                 0x010054
 
+/* inode appears to be a directory */
+#define PR_1_TREAT_AS_DIRECTORY                0x010055
+
 /*
  * Pass 1b errors
  */

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