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dev-cache: skip scanning known blockless dirs

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Skip scan and stat() for dirs and nodes within known /dev/ paths,
where no block devices are located.

Also strlen(_cache.dev_dir) just once.

TODO: add more dirs to _no_scan (configurable via lvm.conf ?)
This commit is contained in:
Zdenek Kabelac 2024-05-22 13:29:35 +02:00
parent d8e639ecba
commit a198224666
1 changed files with 27 additions and 2 deletions
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29
lib/device/dev-cache.c
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@ -53,6 +53,7 @@ static struct {
struct dm_regex *preferred_names_matcher; struct dm_regex *preferred_names_matcher;
const char *dev_dir; const char *dev_dir;
size_t dev_dir_len;
int has_scanned; int has_scanned;
dev_t st_dev; dev_t st_dev;
struct dm_list dirs; struct dm_list dirs;
@ -205,10 +206,9 @@ static int _builtin_preference(const char *path0, const char *path1,
static int _apply_builtin_path_preference_rules(const char *path0, const char *path1) static int _apply_builtin_path_preference_rules(const char *path0, const char *path1)
{ {
size_t devdir_len; size_t devdir_len = _cache.dev_dir_len;
int r; int r;
devdir_len = strlen(_cache.dev_dir);
if (!strncmp(path0, _cache.dev_dir, devdir_len) && if (!strncmp(path0, _cache.dev_dir, devdir_len) &&
!strncmp(path1, _cache.dev_dir, devdir_len)) { !strncmp(path1, _cache.dev_dir, devdir_len)) {
@ -878,6 +878,20 @@ static size_t _collapse_slashes(char *str)
static int _insert_dir(const char *dir) static int _insert_dir(const char *dir)
{ {
/* alphanetically! sorted list used by bsearch of
* /dev subdirectories that should not contain
* any block device, so no reason to scan them. */
static const char _no_scan[][12] = {
"bsg/",
"bus/",
"char/",
"cpu/",
"dma_heap/",
"dri/",
"input/",
"snd/",
"usb/",
};
int n, dirent_count, r = 1; int n, dirent_count, r = 1;
struct dirent **dirent = NULL; struct dirent **dirent = NULL;
char path[PATH_MAX]; char path[PATH_MAX];
@ -892,6 +906,16 @@ static int _insert_dir(const char *dir)
if (len && path[len - 1] != '/') if (len && path[len - 1] != '/')
path[len++] = '/'; path[len++] = '/';
if ((len < (5 + sizeof(_no_scan[0]))) && (strncmp("/dev/", path, 5) == 0) && (len > 5)) {
path[len] = 0;
if (bsearch(path + 5, _no_scan, DM_ARRAY_SIZE(_no_scan), sizeof(_no_scan[0]),
(int (*)(const void*, const void*))strcmp)) {
/* Skip insertion of directories that can't have block devices */
log_debug("Skipping \"%s\" (no block devices).", path);
return 1;
}
}
dirent_count = scandir(dir, &dirent, NULL, alphasort); dirent_count = scandir(dir, &dirent, NULL, alphasort);
if (dirent_count > 0) { if (dirent_count > 0) {
for (n = 0; n < dirent_count; n++) { for (n = 0; n < dirent_count; n++) {
@ -1321,6 +1345,7 @@ int dev_cache_init(struct cmd_context *cmd)
goto bad; goto bad;
} }
_cache.dev_dir_len = strlen(_cache.dev_dir);
dm_list_init(&_cache.dirs); dm_list_init(&_cache.dirs);
if (!_init_preferred_names(cmd)) if (!_init_preferred_names(cmd))