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Diffstat (limited to 'libmount/src/cache.c')
| -rw-r--r-- | libmount/src/cache.c | 840 |
1 files changed, 840 insertions, 0 deletions
diff --git a/libmount/src/cache.c b/libmount/src/cache.c new file mode 100644 index 0000000..2fafdd0 --- /dev/null +++ b/libmount/src/cache.c @@ -0,0 +1,840 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +/* + * This file is part of libmount from util-linux project. + * + * Copyright (C) 2009-2018 Karel Zak <kzak@redhat.com> + * + * libmount is free software; you can redistribute it and/or modify it + * under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 2.1 of the License, or + * (at your option) any later version. + */ + +/** + * SECTION: cache + * @title: Cache + * @short_description: paths and tags (UUID/LABEL) caching + * + * The cache is a very simple API for working with tags (LABEL, UUID, ...) and + * paths. The cache uses libblkid as a backend for TAGs resolution. + * + * All returned paths are always canonicalized. + */ +#include <string.h> +#include <stdlib.h> +#include <ctype.h> +#include <limits.h> +#include <sys/stat.h> +#include <unistd.h> +#include <fcntl.h> +#include <blkid.h> + +#include "canonicalize.h" +#include "mountP.h" +#include "loopdev.h" +#include "strutils.h" + +/* + * Canonicalized (resolved) paths & tags cache + */ +#define MNT_CACHE_CHUNKSZ 128 + +#define MNT_CACHE_ISTAG (1 << 1) /* entry is TAG */ +#define MNT_CACHE_ISPATH (1 << 2) /* entry is path */ +#define MNT_CACHE_TAGREAD (1 << 3) /* tag read by mnt_cache_read_tags() */ + +/* path cache entry */ +struct mnt_cache_entry { + char *key; /* search key (e.g. uncanonicalized path) */ + char *value; /* value (e.g. canonicalized path) */ + int flag; +}; + +struct libmnt_cache { + struct mnt_cache_entry *ents; + size_t nents; + size_t nallocs; + int refcount; + + /* blkid_evaluate_tag() works in two ways: + * + * 1/ all tags are evaluated by udev /dev/disk/by-* symlinks, + * then the blkid_cache is NULL. + * + * 2/ all tags are read from blkid.tab and verified by /dev + * scanning, then the blkid_cache is not NULL and then it's + * better to reuse the blkid_cache. + */ + blkid_cache bc; + + struct libmnt_table *mtab; +}; + +/** + * mnt_new_cache: + * + * Returns: new struct libmnt_cache instance or NULL in case of ENOMEM error. + */ +struct libmnt_cache *mnt_new_cache(void) +{ + struct libmnt_cache *cache = calloc(1, sizeof(*cache)); + if (!cache) + return NULL; + DBG(CACHE, ul_debugobj(cache, "alloc")); + cache->refcount = 1; + return cache; +} + +/** + * mnt_free_cache: + * @cache: pointer to struct libmnt_cache instance + * + * Deallocates the cache. This function does not care about reference count. Don't + * use this function directly -- it's better to use mnt_unref_cache(). + */ +void mnt_free_cache(struct libmnt_cache *cache) +{ + size_t i; + + if (!cache) + return; + + DBG(CACHE, ul_debugobj(cache, "free [refcount=%d]", cache->refcount)); + + for (i = 0; i < cache->nents; i++) { + struct mnt_cache_entry *e = &cache->ents[i]; + if (e->value != e->key) + free(e->value); + free(e->key); + } + free(cache->ents); + if (cache->bc) + blkid_put_cache(cache->bc); + free(cache); +} + +/** + * mnt_ref_cache: + * @cache: cache pointer + * + * Increments reference counter. + */ +void mnt_ref_cache(struct libmnt_cache *cache) +{ + if (cache) { + cache->refcount++; + /*DBG(CACHE, ul_debugobj(cache, "ref=%d", cache->refcount));*/ + } +} + +/** + * mnt_unref_cache: + * @cache: cache pointer + * + * De-increments reference counter, on zero the cache is automatically + * deallocated by mnt_free_cache(). + */ +void mnt_unref_cache(struct libmnt_cache *cache) +{ + if (cache) { + cache->refcount--; + /*DBG(CACHE, ul_debugobj(cache, "unref=%d", cache->refcount));*/ + if (cache->refcount <= 0) { + mnt_unref_table(cache->mtab); + + mnt_free_cache(cache); + } + } +} + +/** + * mnt_cache_set_targets: + * @cache: cache pointer + * @mtab: table with already canonicalized mountpoints + * + * Add to @cache reference to @mtab. This can be used to avoid unnecessary paths + * canonicalization in mnt_resolve_target(). + * + * Returns: negative number in case of error, or 0 o success. + */ +int mnt_cache_set_targets(struct libmnt_cache *cache, + struct libmnt_table *mtab) +{ + if (!cache) + return -EINVAL; + + mnt_ref_table(mtab); + mnt_unref_table(cache->mtab); + cache->mtab = mtab; + return 0; +} + + +/* note that the @key could be the same pointer as @value */ +static int cache_add_entry(struct libmnt_cache *cache, char *key, + char *value, int flag) +{ + struct mnt_cache_entry *e; + + assert(cache); + assert(value); + assert(key); + + if (cache->nents == cache->nallocs) { + size_t sz = cache->nallocs + MNT_CACHE_CHUNKSZ; + + e = realloc(cache->ents, sz * sizeof(struct mnt_cache_entry)); + if (!e) + return -ENOMEM; + cache->ents = e; + cache->nallocs = sz; + } + + e = &cache->ents[cache->nents]; + e->key = key; + e->value = value; + e->flag = flag; + cache->nents++; + + DBG(CACHE, ul_debugobj(cache, "add entry [%2zd] (%s): %s: %s", + cache->nents, + (flag & MNT_CACHE_ISPATH) ? "path" : "tag", + value, key)); + return 0; +} + +/* add tag to the cache, @devname has to be an allocated string */ +static int cache_add_tag(struct libmnt_cache *cache, const char *tagname, + const char *tagval, char *devname, int flag) +{ + size_t tksz, vlsz; + char *key; + int rc; + + assert(cache); + assert(devname); + assert(tagname); + assert(tagval); + + /* add into cache -- cache format for TAGs is + * key = "TAG_NAME\0TAG_VALUE\0" + * value = "/dev/foo" + */ + tksz = strlen(tagname); + vlsz = strlen(tagval); + + key = malloc(tksz + vlsz + 2); + if (!key) + return -ENOMEM; + + memcpy(key, tagname, tksz + 1); /* include '\0' */ + memcpy(key + tksz + 1, tagval, vlsz + 1); + + rc = cache_add_entry(cache, key, devname, flag | MNT_CACHE_ISTAG); + if (!rc) + return 0; + + free(key); + return rc; +} + + +/* + * Returns cached canonicalized path or NULL. + */ +static const char *cache_find_path(struct libmnt_cache *cache, const char *path) +{ + size_t i; + + if (!cache || !path) + return NULL; + + for (i = 0; i < cache->nents; i++) { + struct mnt_cache_entry *e = &cache->ents[i]; + if (!(e->flag & MNT_CACHE_ISPATH)) + continue; + if (streq_paths(path, e->key)) + return e->value; + } + return NULL; +} + +/* + * Returns cached path or NULL. + */ +static const char *cache_find_tag(struct libmnt_cache *cache, + const char *token, const char *value) +{ + size_t i; + size_t tksz; + + if (!cache || !token || !value) + return NULL; + + tksz = strlen(token); + + for (i = 0; i < cache->nents; i++) { + struct mnt_cache_entry *e = &cache->ents[i]; + if (!(e->flag & MNT_CACHE_ISTAG)) + continue; + if (strcmp(token, e->key) == 0 && + strcmp(value, e->key + tksz + 1) == 0) + return e->value; + } + return NULL; +} + +static char *cache_find_tag_value(struct libmnt_cache *cache, + const char *devname, const char *token) +{ + size_t i; + + assert(cache); + assert(devname); + assert(token); + + for (i = 0; i < cache->nents; i++) { + struct mnt_cache_entry *e = &cache->ents[i]; + if (!(e->flag & MNT_CACHE_ISTAG)) + continue; + if (strcmp(e->value, devname) == 0 && /* dev name */ + strcmp(token, e->key) == 0) /* tag name */ + return e->key + strlen(token) + 1; /* tag value */ + } + + return NULL; +} + +/** + * mnt_cache_read_tags + * @cache: pointer to struct libmnt_cache instance + * @devname: path device + * + * Reads @devname LABEL and UUID to the @cache. + * + * Returns: 0 if at least one tag was added, 1 if no tag was added or + * negative number in case of error. + */ +int mnt_cache_read_tags(struct libmnt_cache *cache, const char *devname) +{ + blkid_probe pr; + size_t i, ntags = 0; + int rc; + const char *tags[] = { "LABEL", "UUID", "TYPE", "PARTUUID", "PARTLABEL" }; + const char *blktags[] = { "LABEL", "UUID", "TYPE", "PART_ENTRY_UUID", "PART_ENTRY_NAME" }; + + if (!cache || !devname) + return -EINVAL; + + DBG(CACHE, ul_debugobj(cache, "tags for %s requested", devname)); + + /* check if device is already cached */ + for (i = 0; i < cache->nents; i++) { + struct mnt_cache_entry *e = &cache->ents[i]; + if (!(e->flag & MNT_CACHE_TAGREAD)) + continue; + if (strcmp(e->value, devname) == 0) + /* tags have already been read */ + return 0; + } + + pr = blkid_new_probe_from_filename(devname); + if (!pr) + return -1; + + blkid_probe_enable_superblocks(pr, 1); + blkid_probe_set_superblocks_flags(pr, + BLKID_SUBLKS_LABEL | BLKID_SUBLKS_UUID | + BLKID_SUBLKS_TYPE); + + blkid_probe_enable_partitions(pr, 1); + blkid_probe_set_partitions_flags(pr, BLKID_PARTS_ENTRY_DETAILS); + + rc = blkid_do_safeprobe(pr); + if (rc) + goto error; + + DBG(CACHE, ul_debugobj(cache, "reading tags for: %s", devname)); + + for (i = 0; i < ARRAY_SIZE(tags); i++) { + const char *data; + char *dev; + + if (cache_find_tag_value(cache, devname, tags[i])) { + DBG(CACHE, ul_debugobj(cache, + "\ntag %s already cached", tags[i])); + continue; + } + if (blkid_probe_lookup_value(pr, blktags[i], &data, NULL)) + continue; + dev = strdup(devname); + if (!dev) + goto error; + if (cache_add_tag(cache, tags[i], data, dev, + MNT_CACHE_TAGREAD)) { + free(dev); + goto error; + } + ntags++; + } + + DBG(CACHE, ul_debugobj(cache, "\tread %zd tags", ntags)); + blkid_free_probe(pr); + return ntags ? 0 : 1; +error: + blkid_free_probe(pr); + return rc < 0 ? rc : -1; +} + +/** + * mnt_cache_device_has_tag: + * @cache: paths cache + * @devname: path to the device + * @token: tag name (e.g "LABEL") + * @value: tag value + * + * Look up @cache to check if @tag+@value are associated with @devname. + * + * Returns: 1 on success or 0. + */ +int mnt_cache_device_has_tag(struct libmnt_cache *cache, const char *devname, + const char *token, const char *value) +{ + const char *path = cache_find_tag(cache, token, value); + + if (path && devname && strcmp(path, devname) == 0) + return 1; + return 0; +} + +static int __mnt_cache_find_tag_value(struct libmnt_cache *cache, + const char *devname, const char *token, char **data) +{ + int rc = 0; + + if (!cache || !devname || !token || !data) + return -EINVAL; + + rc = mnt_cache_read_tags(cache, devname); + if (rc) + return rc; + + *data = cache_find_tag_value(cache, devname, token); + return *data ? 0 : -1; +} + +/** + * mnt_cache_find_tag_value: + * @cache: cache for results + * @devname: device name + * @token: tag name ("LABEL" or "UUID") + * + * Returns: LABEL or UUID for the @devname or NULL in case of error. + */ +char *mnt_cache_find_tag_value(struct libmnt_cache *cache, + const char *devname, const char *token) +{ + char *data = NULL; + + if (__mnt_cache_find_tag_value(cache, devname, token, &data) == 0) + return data; + return NULL; +} + +/** + * mnt_get_fstype: + * @devname: device name + * @ambi: returns TRUE if probing result is ambivalent (optional argument) + * @cache: cache for results or NULL + * + * Returns: filesystem type or NULL in case of error. The result has to be + * deallocated by free() if @cache is NULL. + */ +char *mnt_get_fstype(const char *devname, int *ambi, struct libmnt_cache *cache) +{ + blkid_probe pr; + const char *data; + char *type = NULL; + int rc; + + DBG(CACHE, ul_debugobj(cache, "get %s FS type", devname)); + + if (cache) { + char *val = NULL; + rc = __mnt_cache_find_tag_value(cache, devname, "TYPE", &val); + if (ambi) + *ambi = rc == -2 ? TRUE : FALSE; + return rc ? NULL : val; + } + + /* + * no cache, probe directly + */ + pr = blkid_new_probe_from_filename(devname); + if (!pr) + return NULL; + + blkid_probe_enable_superblocks(pr, 1); + blkid_probe_set_superblocks_flags(pr, BLKID_SUBLKS_TYPE); + + rc = blkid_do_safeprobe(pr); + + DBG(CACHE, ul_debugobj(cache, "libblkid rc=%d", rc)); + + if (!rc && !blkid_probe_lookup_value(pr, "TYPE", &data, NULL)) + type = strdup(data); + + if (ambi) + *ambi = rc == -2 ? TRUE : FALSE; + + blkid_free_probe(pr); + return type; +} + +static char *canonicalize_path_and_cache(const char *path, + struct libmnt_cache *cache) +{ + char *p; + char *key; + char *value; + + DBG(CACHE, ul_debugobj(cache, "canonicalize path %s", path)); + p = canonicalize_path(path); + + if (p && cache) { + value = p; + key = strcmp(path, p) == 0 ? value : strdup(path); + + if (!key || !value) + goto error; + + if (cache_add_entry(cache, key, value, + MNT_CACHE_ISPATH)) + goto error; + } + + return p; +error: + if (value != key) + free(value); + free(key); + return NULL; +} + +/** + * mnt_resolve_path: + * @path: "native" path + * @cache: cache for results or NULL + * + * Converts path: + * - to the absolute path + * - /dev/dm-N to /dev/mapper/name + * + * Returns: absolute path or NULL in case of error. The result has to be + * deallocated by free() if @cache is NULL. + */ +char *mnt_resolve_path(const char *path, struct libmnt_cache *cache) +{ + char *p = NULL; + + /*DBG(CACHE, ul_debugobj(cache, "resolving path %s", path));*/ + + if (!path) + return NULL; + if (cache) + p = (char *) cache_find_path(cache, path); + if (!p) + p = canonicalize_path_and_cache(path, cache); + + return p; +} + +/** + * mnt_resolve_target: + * @path: "native" path, a potential mount point + * @cache: cache for results or NULL. + * + * Like mnt_resolve_path(), unless @cache is not NULL and + * mnt_cache_set_targets(cache, mtab) was called: if @path is found in the + * cached @mtab and the matching entry was provided by the kernel, assume that + * @path is already canonicalized. By avoiding a call to realpath(2) on + * known mount points, there is a lower risk of stepping on a stale mount + * point, which can result in an application freeze. This is also faster in + * general, as stat(2) on a mount point is slower than on a regular file. + * + * Returns: absolute path or NULL in case of error. The result has to be + * deallocated by free() if @cache is NULL. + */ +char *mnt_resolve_target(const char *path, struct libmnt_cache *cache) +{ + char *p = NULL; + + /*DBG(CACHE, ul_debugobj(cache, "resolving target %s", path));*/ + + if (!cache || !cache->mtab) + return mnt_resolve_path(path, cache); + + p = (char *) cache_find_path(cache, path); + if (p) + return p; + + { + struct libmnt_iter itr; + struct libmnt_fs *fs = NULL; + + mnt_reset_iter(&itr, MNT_ITER_BACKWARD); + while (mnt_table_next_fs(cache->mtab, &itr, &fs) == 0) { + + if (!mnt_fs_is_kernel(fs) + || mnt_fs_is_swaparea(fs) + || !mnt_fs_streq_target(fs, path)) + continue; + + p = strdup(path); + if (!p) + return NULL; /* ENOMEM */ + + if (cache_add_entry(cache, p, p, MNT_CACHE_ISPATH)) { + free(p); + return NULL; /* ENOMEM */ + } + break; + } + } + + if (!p) + p = canonicalize_path_and_cache(path, cache); + return p; +} + +/** + * mnt_pretty_path: + * @path: any path + * @cache: NULL or pointer to the cache + * + * Converts path: + * - to the absolute path + * - /dev/dm-N to /dev/mapper/name + * - /dev/loopN to the loop backing filename + * - empty path (NULL) to 'none' + * + * Returns: newly allocated string with path, result always has to be deallocated + * by free(). + */ +char *mnt_pretty_path(const char *path, struct libmnt_cache *cache) +{ + char *pretty = mnt_resolve_path(path, cache); + + if (!pretty) + return strdup("none"); + +#ifdef __linux__ + /* users assume backing file name rather than /dev/loopN in + * output if the device has been initialized by mount(8). + */ + if (strncmp(pretty, "/dev/loop", 9) == 0) { + struct loopdev_cxt lc; + + if (loopcxt_init(&lc, 0) || loopcxt_set_device(&lc, pretty)) + goto done; + + if (loopcxt_is_autoclear(&lc)) { + char *tmp = loopcxt_get_backing_file(&lc); + if (tmp) { + loopcxt_deinit(&lc); + if (!cache) + free(pretty); /* not cached, deallocate */ + return tmp; /* return backing file */ + } + } + loopcxt_deinit(&lc); + + } +#endif + +done: + /* don't return pointer to the cache, allocate a new string */ + return cache ? strdup(pretty) : pretty; +} + +/** + * mnt_resolve_tag: + * @token: tag name + * @value: tag value + * @cache: for results or NULL + * + * Returns: device name or NULL in case of error. The result has to be + * deallocated by free() if @cache is NULL. + */ +char *mnt_resolve_tag(const char *token, const char *value, + struct libmnt_cache *cache) +{ + char *p = NULL; + + /*DBG(CACHE, ul_debugobj(cache, "resolving tag token=%s value=%s", + token, value));*/ + + if (!token || !value) + return NULL; + + if (cache) + p = (char *) cache_find_tag(cache, token, value); + + if (!p) { + /* returns newly allocated string */ + p = blkid_evaluate_tag(token, value, cache ? &cache->bc : NULL); + + if (p && cache && + cache_add_tag(cache, token, value, p, 0)) + goto error; + } + + return p; +error: + free(p); + return NULL; +} + + + +/** + * mnt_resolve_spec: + * @spec: path or tag + * @cache: paths cache + * + * Returns: canonicalized path or NULL. The result has to be + * deallocated by free() if @cache is NULL. + */ +char *mnt_resolve_spec(const char *spec, struct libmnt_cache *cache) +{ + char *cn = NULL; + char *t = NULL, *v = NULL; + + if (!spec) + return NULL; + + if (blkid_parse_tag_string(spec, &t, &v) == 0 && mnt_valid_tagname(t)) + cn = mnt_resolve_tag(t, v, cache); + else + cn = mnt_resolve_path(spec, cache); + + free(t); + free(v); + return cn; +} + + +#ifdef TEST_PROGRAM + +static int test_resolve_path(struct libmnt_test *ts, int argc, char *argv[]) +{ + char line[BUFSIZ]; + struct libmnt_cache *cache; + + cache = mnt_new_cache(); + if (!cache) + return -ENOMEM; + + while(fgets(line, sizeof(line), stdin)) { + size_t sz = strlen(line); + char *p; + + if (sz > 0 && line[sz - 1] == '\n') + line[sz - 1] = '\0'; + + p = mnt_resolve_path(line, cache); + printf("%s : %s\n", line, p); + } + mnt_unref_cache(cache); + return 0; +} + +static int test_resolve_spec(struct libmnt_test *ts, int argc, char *argv[]) +{ + char line[BUFSIZ]; + struct libmnt_cache *cache; + + cache = mnt_new_cache(); + if (!cache) + return -ENOMEM; + + while(fgets(line, sizeof(line), stdin)) { + size_t sz = strlen(line); + char *p; + + if (sz > 0 && line[sz - 1] == '\n') + line[sz - 1] = '\0'; + + p = mnt_resolve_spec(line, cache); + printf("%s : %s\n", line, p); + } + mnt_unref_cache(cache); + return 0; +} + +static int test_read_tags(struct libmnt_test *ts, int argc, char *argv[]) +{ + char line[BUFSIZ]; + struct libmnt_cache *cache; + size_t i; + + cache = mnt_new_cache(); + if (!cache) + return -ENOMEM; + + while(fgets(line, sizeof(line), stdin)) { + size_t sz = strlen(line); + char *t = NULL, *v = NULL; + + if (sz > 0 && line[sz - 1] == '\n') + line[sz - 1] = '\0'; + + if (!strcmp(line, "quit")) + break; + + if (*line == '/') { + if (mnt_cache_read_tags(cache, line) < 0) + fprintf(stderr, "%s: read tags failed\n", line); + + } else if (blkid_parse_tag_string(line, &t, &v) == 0) { + const char *cn = NULL; + + if (mnt_valid_tagname(t)) + cn = cache_find_tag(cache, t, v); + free(t); + free(v); + + if (cn) + printf("%s: %s\n", line, cn); + else + printf("%s: not cached\n", line); + } + } + + for (i = 0; i < cache->nents; i++) { + struct mnt_cache_entry *e = &cache->ents[i]; + if (!(e->flag & MNT_CACHE_ISTAG)) + continue; + + printf("%15s : %5s : %s\n", e->value, e->key, + e->key + strlen(e->key) + 1); + } + + mnt_unref_cache(cache); + return 0; + +} + +int main(int argc, char *argv[]) +{ + struct libmnt_test ts[] = { + { "--resolve-path", test_resolve_path, " resolve paths from stdin" }, + { "--resolve-spec", test_resolve_spec, " evaluate specs from stdin" }, + { "--read-tags", test_read_tags, " read devname or TAG from stdin (\"quit\" to exit)" }, + { NULL } + }; + + return mnt_run_test(ts, argc, argv); +} +#endif |