2009-02-13 Jim Meyering <meyering@redhat.com>
+ fts: arrange not to stat non-directories in more cases
+ This makes GNU find (when it doesn't need to stat each file)
+ *much* more efficient at traversing reiserfs file systems.
+ * lib/fts_.h (struct ftsent) [fts_n_dirs_remaining]: New member.
+ (struct FTS) [fts_leaf_optimization_works_ht]: Add member.
+ * lib/fts.c (fts_close): Free ->fts_leaf_optimization_works_ht.
+ (S_MAGIC_REISERFS, S_MAGIC_PROC): Define.
+ (leaf_optimization_applies): New function.
+ (LCO_hash, LCO_compare): New helper functions.
+ (link_count_optimize_ok): New function.
+ (fts_stat): Initialize new member (if dir).
+ (fts_read): Decrement parent's fts_n_dirs_remaining count if
+ we've just stat'ed a directory. Skip the stat call when possible.
+ ---
+ Note this AFS-related exchange:
+ http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=143111
+ and note find's pioctl call in find/fstype.c.
+ But that is necessary only if you want to enable the
+ optimization for AFS, and for now, I don't.
+
fts: move a function definition "up" (no semantic change)
* lib/fts.c (dirent_inode_sort_may_be_useful): Move definition
"up" to precede upcoming use of a related function.
}
fd_ring_clear (&sp->fts_fd_ring);
+
+ if (sp->fts_leaf_optimization_works_ht)
+ hash_free (sp->fts_leaf_optimization_works_ht);
+
free_dir (sp);
/* Free up the stream pointer. */
/* Linux-specific constants from coreutils' src/fs.h */
# define S_MAGIC_TMPFS 0x1021994
# define S_MAGIC_NFS 0x6969
+# define S_MAGIC_REISERFS 0x52654973
+# define S_MAGIC_PROC 0x9FA0
/* Return false if it is easy to determine the file system type of
the directory on which DIR_FD is open, and sorting dirents on
return true;
}
}
+
+/* Given a file descriptor DIR_FD open on a directory D,
+ return true if it is valid to apply the leaf-optimization
+ technique of counting directories in D via stat.st_nlink. */
+static bool
+leaf_optimization_applies (int dir_fd)
+{
+ struct statfs fs_buf;
+
+ /* If fstatfs fails, assume we can't use the optimization. */
+ if (fstatfs (dir_fd, &fs_buf) != 0)
+ return false;
+
+ /* FIXME: do we need to detect AFS mount points? I doubt it,
+ unless fstatfs can report S_MAGIC_REISERFS for such a directory. */
+
+ switch (fs_buf.f_type)
+ {
+ /* List here the file system types that lack useable dirent.d_type
+ info, yet for which the optimization does apply. */
+ case S_MAGIC_REISERFS:
+ return true;
+
+ case S_MAGIC_PROC:
+ /* Explicitly listing this or any other file system type for which
+ the optimization is not applicable is not necessary, but we leave
+ it here to document the risk. Per http://bugs.debian.org/143111,
+ /proc may have bogus stat.st_nlink values. */
+ /* fall through */
+ default:
+ return false;
+ }
+}
+
#else
static bool dirent_inode_sort_may_be_useful (int dir_fd) { return true; }
+static bool leaf_optimization_applies (int dir_fd) { return false; }
#endif
+/* link-count-optimization entry:
+ map an stat.st_dev number to a boolean: leaf_optimization_works */
+struct LCO_ent
+{
+ dev_t st_dev;
+ bool opt_ok;
+};
+
+/* Use a tiny initial size. If a traversal encounters more than
+ a few devices, the cost of growing/rehashing this table will be
+ rendered negligible by the number of inodes processed. */
+enum { LCO_HT_INITIAL_SIZE = 13 };
+
+static size_t
+LCO_hash (void const *x, size_t table_size)
+{
+ struct LCO_ent const *ax = x;
+ return (uintmax_t) ax->st_dev % table_size;
+}
+
+static bool
+LCO_compare (void const *x, void const *y)
+{
+ struct LCO_ent const *ax = x;
+ struct LCO_ent const *ay = y;
+ return ax->st_dev == ay->st_dev;
+}
+
+/* Ask the same question as leaf_optimization_applies, but query
+ the cache first (FTS.fts_leaf_optimization_works_ht), and if necessary,
+ update that cache. */
+static bool
+link_count_optimize_ok (FTSENT const *p)
+{
+ FTS *sp = p->fts_fts;
+ Hash_table *h = sp->fts_leaf_optimization_works_ht;
+ struct LCO_ent tmp;
+ struct LCO_ent *ent;
+ bool opt_ok;
+ struct LCO_ent *t2;
+
+ /* If we're not in CWDFD mode, don't bother with this optimization,
+ since the caller is not serious about performance. */
+ if (!ISSET(FTS_CWDFD))
+ return false;
+
+ /* map st_dev to the boolean, leaf_optimization_works */
+ if (h == NULL)
+ {
+ h = sp->fts_leaf_optimization_works_ht
+ = hash_initialize (LCO_HT_INITIAL_SIZE, NULL, LCO_hash,
+ LCO_compare, free);
+ if (h == NULL)
+ return false;
+ }
+ tmp.st_dev = p->fts_statp->st_dev;
+ ent = hash_lookup (h, &tmp);
+ if (ent)
+ return ent->opt_ok;
+
+ /* Look-up failed. Query directly and cache the result. */
+ t2 = malloc (sizeof *t2);
+ if (t2 == NULL)
+ return false;
+
+ /* Is it ok to perform the optimization in the dir, FTS_CWD_FD? */
+ opt_ok = leaf_optimization_applies (sp->fts_cwd_fd);
+ t2->opt_ok = opt_ok;
+ t2->st_dev = p->fts_statp->st_dev;
+
+ ent = hash_insert (h, t2);
+ if (ent == NULL)
+ {
+ /* insertion failed */
+ free (t2);
+ return false;
+ }
+ fts_assert (ent == t2);
+
+ return opt_ok;
+}
+
/*
* Special case of "/" at the end of the file name so that slashes aren't
* appended which would cause file names to be written as "....//foo".
if (p->fts_info == FTS_NSOK)
{
if (p->fts_statp->st_size == FTS_STAT_REQUIRED)
- p->fts_info = fts_stat(sp, p, false);
+ {
+ FTSENT *parent = p->fts_parent;
+ if (parent->fts_n_dirs_remaining == 0
+ && ISSET(FTS_NOSTAT)
+ && ISSET(FTS_PHYSICAL)
+ && link_count_optimize_ok (parent))
+ {
+ /* nothing more needed */
+ }
+ else
+ {
+ p->fts_info = fts_stat(sp, p, false);
+ if (S_ISDIR(p->fts_statp->st_mode))
+ {
+ if (parent->fts_n_dirs_remaining)
+ parent->fts_n_dirs_remaining--;
+ }
+ }
+ }
else
fts_assert (p->fts_statp->st_size == FTS_NO_STAT_REQUIRED);
}
}
if (S_ISDIR(sbp->st_mode)) {
+ p->fts_n_dirs_remaining = (sbp->st_nlink
+ - (ISSET(FTS_SEEDOT) ? 0 : 2));
if (ISDOT(p->fts_name)) {
/* Command-line "." and ".." are real directories. */
return (p->fts_level == FTS_ROOTLEVEL ? FTS_D : FTS_DOT);
/* Traverse a file hierarchy.
- Copyright (C) 2004-2008 Free Software Foundation, Inc.
+ Copyright (C) 2004-2009 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
int fts_options; /* fts_open options, global flags */
# if GNULIB_FTS
+ /* Map a directory's device number to a boolean. The boolean is
+ true if for that file system (type determined by a single fstatfs
+ call per FS) st_nlink can be used to calculate the number of
+ sub-directory entries in a directory.
+ Using this table is an optimization that permits us to look up
+ file system type on a per-inode basis at the minimal cost of
+ calling fstatfs only once per traversed device. */
+ struct hash_table *fts_leaf_optimization_works_ht;
+
union {
/* This data structure is used if FTS_TIGHT_CYCLE_CHECK is
specified. It records the directories between a starting
ptrdiff_t fts_level; /* depth (-1 to N) */
size_t fts_namelen; /* strlen(fts_name) */
+ nlink_t fts_n_dirs_remaining; /* count down from st_nlink */
# define FTS_D 1 /* preorder directory */
# define FTS_DC 2 /* directory that causes cycles */
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