From b9f9ed14bda93ecb407129b69e6476813c250046 Mon Sep 17 00:00:00 2001

From: Paul Eggert <eggert@cs.ucla.edu>

Date: Wed, 15 Apr 2020 20:50:32 -0700

Subject: [PATCH] fts: remove NOSTAT_LEAF_OPTIMIZATION

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It caused ‘find’ and ‘du’ to dump core, and it was useful

only for obsolescent Linux filesystems anyway.  Problem reported in:

https://lists.gnu.org/r/bug-gnulib/2020-04/msg00068.html

Quite possibly there is still a serious underlying fts bug with

tight-loop-check and mutating file systems, but if so this patch

should cause the bug to be triggered less often.

* lib/fts.c (enum leaf_optimization): Remove

NOSTAT_LEAF_OPTIMIZATION, as it’s problematic.

(S_MAGIC_REISERFS, S_MAGIC_XFS): Remove; no longer needed.

(leaf_optimization): Remove special cases for ReiserFS and XFS.

(fts_read): Remove NOSTAT_LEAF_OPTIMIZATION code.

* lib/fts_.h (struct _ftsent.fts_n_dirs_remaining):

Remove.  All uses removed.

Upstream-commit: 47bf2cf3184027c1eb9c1dfeea5c5b8b2d69710d

Signed-off-by: Kamil Dudka <kdudka@redhat.com>

---

 lib/fts.c  | 56 ++++++++-------------------------------------------

 lib/fts_.h |  5 -----

 2 files changed, 8 insertions(+), 53 deletions(-)

diff --git a/lib/fts.c b/lib/fts.c

index 1093ce5..dfe3fef 100644

--- a/lib/fts.c

+++ b/lib/fts.c

@@ -445,7 +445,6 @@ fts_open (char * const *argv,

                 if ((parent = fts_alloc(sp, "", 0)) == NULL)

                         goto mem2;

                 parent->fts_level = FTS_ROOTPARENTLEVEL;

-                parent->fts_n_dirs_remaining = -1;

           }

         /* The classic fts implementation would call fts_stat with

@@ -634,9 +633,8 @@ fts_close (FTS *sp)

 }

 /* Minimum link count of a traditional Unix directory.  When leaf

-   optimization is OK and MIN_DIR_NLINK <= st_nlink, then st_nlink is

-   an upper bound on the number of subdirectories (counting "." and

-   "..").  */

+   optimization is OK and a directory's st_nlink == MIN_DIR_NLINK,

+   then the directory has no subdirectories.  */

 enum { MIN_DIR_NLINK = 2 };

 /* Whether leaf optimization is OK for a directory.  */

@@ -645,12 +643,8 @@ enum leaf_optimization

     /* st_nlink is not reliable for this directory's subdirectories.  */

     NO_LEAF_OPTIMIZATION,

-    /* Leaf optimization is OK, but is not useful for avoiding stat calls.  */

-    OK_LEAF_OPTIMIZATION,

-

-    /* Leaf optimization is not only OK: it is useful for avoiding

-       stat calls, because dirent.d_type does not work.  */

-    NOSTAT_LEAF_OPTIMIZATION

+    /* st_nlink == 2 means the directory lacks subdirectories.  */

+    OK_LEAF_OPTIMIZATION

   };

 #if (defined __linux__ || defined __ANDROID__) \

@@ -663,9 +657,7 @@ enum leaf_optimization

 # define S_MAGIC_CIFS 0xFF534D42

 # define S_MAGIC_NFS 0x6969

 # define S_MAGIC_PROC 0x9FA0

-# define S_MAGIC_REISERFS 0x52654973

 # define S_MAGIC_TMPFS 0x1021994

-# define S_MAGIC_XFS 0x58465342

 # ifdef HAVE___FSWORD_T

 typedef __fsword_t fsword;

@@ -786,23 +778,15 @@ dirent_inode_sort_may_be_useful (FTSENT const *p, int dir_fd)

 }

 /* Given an FTS entry P for a directory with descriptor DIR_FD,

-   return true if it is both useful and valid to apply leaf optimization.

-   The optimization is useful only for file systems that lack usable

-   dirent.d_type info.  The optimization is valid if an st_nlink value

-   of at least MIN_DIR_NLINK is an upper bound on the number of

-   subdirectories of D, counting "." and ".."  as subdirectories.

+   return whether it is valid to apply leaf optimization.

+   The optimization is valid if a directory's st_nlink value equal

+   to MIN_DIR_NLINK means the directory has no subdirectories.

    DIR_FD is negative if unavailable.  */

 static enum leaf_optimization

 leaf_optimization (FTSENT const *p, int dir_fd)

 {

   switch (filesystem_type (p, dir_fd))

     {

-      /* List here the file system types that may lack usable dirent.d_type

-         info, yet for which the optimization does apply.  */

-    case S_MAGIC_REISERFS:

-    case S_MAGIC_XFS: /* XFS lacked it until 2013-08-22 commit.  */

-      return NOSTAT_LEAF_OPTIMIZATION;

-

     case 0:

       /* Leaf optimization is unsafe if the file system type is unknown.  */

       FALLTHROUGH;

@@ -1027,26 +1011,7 @@ check_for_dir:

                 if (p->fts_info == FTS_NSOK)

                   {

                     if (p->fts_statp->st_size == FTS_STAT_REQUIRED)

-                      {

-                        FTSENT *parent = p->fts_parent;

-                        if (parent->fts_n_dirs_remaining == 0

-                            && ISSET(FTS_NOSTAT)

-                            && ISSET(FTS_PHYSICAL)

-                            && (leaf_optimization (parent, sp->fts_cwd_fd)

-                                == NOSTAT_LEAF_OPTIMIZATION))

-                          {

-                            /* nothing more needed */

-                          }

-                        else

-                          {

-                            p->fts_info = fts_stat(sp, p, false);

-                            if (S_ISDIR(p->fts_statp->st_mode)

-                                && p->fts_level != FTS_ROOTLEVEL

-                                && 0 < parent->fts_n_dirs_remaining

-                                && parent->fts_n_dirs_remaining != (nlink_t) -1)

-                                  parent->fts_n_dirs_remaining--;

-                          }

-                      }

+                      p->fts_info = fts_stat(sp, p, false);

                     else

                       fts_assert (p->fts_statp->st_size == FTS_NO_STAT_REQUIRED);

                   }

@@ -1830,11 +1795,6 @@ err:            memset(sbp, 0, sizeof(struct stat));

         }

         if (S_ISDIR(sbp->st_mode)) {

-                p->fts_n_dirs_remaining

-                  = ((sbp->st_nlink < MIN_DIR_NLINK

-                      || p->fts_level <= FTS_ROOTLEVEL)

-                     ? -1

-                     : sbp->st_nlink - (ISSET (FTS_SEEDOT) ? 0 : MIN_DIR_NLINK));

                 if (ISDOT(p->fts_name)) {

                         /* Command-line "." and ".." are real directories. */

                         return (p->fts_level == FTS_ROOTLEVEL ? FTS_D : FTS_DOT);

diff --git a/lib/fts_.h b/lib/fts_.h

index d40a116..2e76cc4 100644

--- a/lib/fts_.h

+++ b/lib/fts_.h

@@ -227,11 +227,6 @@ typedef struct _ftsent {

         size_t fts_namelen;             /* strlen(fts_name) */

-        /* If not (nlink_t) -1, an upper bound on the number of

-           remaining subdirectories of interest.  If this becomes

-           zero, some work can be avoided.  */

-        nlink_t fts_n_dirs_remaining;

-

 # define FTS_D           1              /* preorder directory */

 # define FTS_DC          2              /* directory that causes cycles */

 # define FTS_DEFAULT     3              /* none of the above */

-- 

2.21.1