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[Qemu-devel] [PATCH 01/13] util/path: Do not cache all filenames at star
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PATCH 01/13] util/path: Do not cache all filenames at startup |
Date: |
Sun, 19 May 2019 13:19:41 -0700 |
If one uses -L $PATH to point to a full chroot, the startup time
is significant. In addition, the existing probing algorithm fails
to handle symlink loops.
Instead, probe individual paths on demand. Cache both positive
and negative results within $PATH, so that any one filename is
probed only once.
Use glib filename functions for clarity.
Signed-off-by: Richard Henderson <address@hidden>
---
util/path.c | 201 ++++++++++++----------------------------------------
1 file changed, 47 insertions(+), 154 deletions(-)
diff --git a/util/path.c b/util/path.c
index 7f9fc272fb..8e174eb436 100644
--- a/util/path.c
+++ b/util/path.c
@@ -8,170 +8,63 @@
#include <dirent.h>
#include "qemu/cutils.h"
#include "qemu/path.h"
+#include "qemu/thread.h"
-struct pathelem
-{
- /* Name of this, eg. lib */
- char *name;
- /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
- char *pathname;
- struct pathelem *parent;
- /* Children */
- unsigned int num_entries;
- struct pathelem *entries[0];
-};
-
-static struct pathelem *base;
-
-/* First N chars of S1 match S2, and S2 is N chars long. */
-static int strneq(const char *s1, unsigned int n, const char *s2)
-{
- unsigned int i;
-
- for (i = 0; i < n; i++)
- if (s1[i] != s2[i])
- return 0;
- return s2[i] == 0;
-}
-
-static struct pathelem *add_entry(struct pathelem *root, const char *name,
- unsigned type);
-
-static struct pathelem *new_entry(const char *root,
- struct pathelem *parent,
- const char *name)
-{
- struct pathelem *new = g_malloc(sizeof(*new));
- new->name = g_strdup(name);
- new->pathname = g_strdup_printf("%s/%s", root, name);
- new->num_entries = 0;
- return new;
-}
-
-#define streq(a,b) (strcmp((a), (b)) == 0)
-
-/* Not all systems provide this feature */
-#if defined(DT_DIR) && defined(DT_UNKNOWN) && defined(DT_LNK)
-# define dirent_type(dirent) ((dirent)->d_type)
-# define is_dir_maybe(type) \
- ((type) == DT_DIR || (type) == DT_UNKNOWN || (type) == DT_LNK)
-#else
-# define dirent_type(dirent) (1)
-# define is_dir_maybe(type) (type)
-#endif
-
-static struct pathelem *add_dir_maybe(struct pathelem *path)
-{
- DIR *dir;
-
- if ((dir = opendir(path->pathname)) != NULL) {
- struct dirent *dirent;
-
- while ((dirent = readdir(dir)) != NULL) {
- if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
- path = add_entry(path, dirent->d_name, dirent_type(dirent));
- }
- }
- closedir(dir);
- }
- return path;
-}
-
-static struct pathelem *add_entry(struct pathelem *root, const char *name,
- unsigned type)
-{
- struct pathelem **e;
-
- root->num_entries++;
-
- root = g_realloc(root, sizeof(*root)
- + sizeof(root->entries[0])*root->num_entries);
- e = &root->entries[root->num_entries-1];
-
- *e = new_entry(root->pathname, root, name);
- if (is_dir_maybe(type)) {
- *e = add_dir_maybe(*e);
- }
-
- return root;
-}
-
-/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
-static void set_parents(struct pathelem *child, struct pathelem *parent)
-{
- unsigned int i;
-
- child->parent = parent;
- for (i = 0; i < child->num_entries; i++)
- set_parents(child->entries[i], child);
-}
-
-/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
-static const char *
-follow_path(const struct pathelem *cursor, const char *name)
-{
- unsigned int i, namelen;
-
- name += strspn(name, "/");
- namelen = strcspn(name, "/");
-
- if (namelen == 0)
- return cursor->pathname;
-
- if (strneq(name, namelen, ".."))
- return follow_path(cursor->parent, name + namelen);
-
- if (strneq(name, namelen, "."))
- return follow_path(cursor, name + namelen);
-
- for (i = 0; i < cursor->num_entries; i++)
- if (strneq(name, namelen, cursor->entries[i]->name))
- return follow_path(cursor->entries[i], name + namelen);
-
- /* Not found */
- return NULL;
-}
+static const char *base;
+static GHashTable *hash;
+static QemuMutex lock;
void init_paths(const char *prefix)
{
- char pref_buf[PATH_MAX];
-
- if (prefix[0] == '\0' ||
- !strcmp(prefix, "/"))
+ if (prefix[0] == '\0' || !strcmp(prefix, "/")) {
return;
-
- if (prefix[0] != '/') {
- char *cwd = getcwd(NULL, 0);
- size_t pref_buf_len = sizeof(pref_buf);
-
- if (!cwd)
- abort();
- pstrcpy(pref_buf, sizeof(pref_buf), cwd);
- pstrcat(pref_buf, pref_buf_len, "/");
- pstrcat(pref_buf, pref_buf_len, prefix);
- free(cwd);
- } else
- pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
-
- base = new_entry("", NULL, pref_buf);
- base = add_dir_maybe(base);
- if (base->num_entries == 0) {
- g_free(base->pathname);
- g_free(base->name);
- g_free(base);
- base = NULL;
- } else {
- set_parents(base, base);
}
+
+ if (prefix[0] == '/') {
+ base = g_strdup(prefix);
+ } else {
+ char *cwd = g_get_current_dir();
+ base = g_build_filename(cwd, prefix, NULL);
+ g_free(cwd);
+ }
+
+ hash = g_hash_table_new(g_str_hash, g_str_equal);
+ qemu_mutex_init(&lock);
}
/* Look for path in emulation dir, otherwise return name. */
const char *path(const char *name)
{
- /* Only do absolute paths: quick and dirty, but should mostly be OK.
- Could do relative by tracking cwd. */
- if (!base || !name || name[0] != '/')
- return name;
+ gpointer key, value;
+ const char *ret;
- return follow_path(base, name) ?: name;
+ /* Only do absolute paths: quick and dirty, but should mostly be OK. */
+ if (!base || !name || name[0] != '/') {
+ return name;
+ }
+
+ qemu_mutex_lock(&lock);
+
+ /* Have we looked up this file before? */
+ if (g_hash_table_lookup_extended(hash, name, &key, &value)) {
+ ret = value ? value : name;
+ } else {
+ char *save = g_strdup(name);
+ char *full = g_build_filename(base, name, NULL);
+
+ /* Look for the path; record the result, pass or fail. */
+ if (access(full, F_OK) == 0) {
+ /* Exists. */
+ g_hash_table_insert(hash, save, full);
+ ret = full;
+ } else {
+ /* Does not exist. */
+ g_free(full);
+ g_hash_table_insert(hash, save, NULL);
+ ret = name;
+ }
+ }
+
+ qemu_mutex_unlock(&lock);
+ return ret;
}
--
2.17.1
- [Qemu-devel] [PATCH 00/13] linux-user: path, clone, sparc, shmat fixes, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 01/13] util/path: Do not cache all filenames at startup,
Richard Henderson <=
- [Qemu-devel] [PATCH 04/13] linux-user/alpha: Set r20 secondary return value, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 02/13] linux-user: Rename cpu_clone_regs to cpu_clone_regs_child, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 03/13] linux-user: Introduce cpu_clone_regs_parent, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 06/13] linux-user/sparc: Use WREG constants in sparc/target_cpu.h, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 05/13] target/sparc: Define an enumeration for accessing env->regwptr, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 08/13] linux-user/sparc: Fix cpu_clone_regs, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 11/13] tests/tcg/multiarch/linux-test: Fix error check for shmat, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 07/13] linux-user/sparc: Use WREG constants in sparc/signal.c, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 09/13] linux-user/sparc: Flush register windows before clone/fork/vfork, Richard Henderson, 2019/05/19
- [Qemu-devel] [PATCH 10/13] scripts/qemu-binfmt-conf: Update for sparc64, Richard Henderson, 2019/05/19