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liblvm: allow config settings to be read without full lvm cmd

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A program may be using liblvm2app for simply checking a config
setting in lvm.conf.  In this case, a full lvm context is not
needed, only cmd->cft (which are the config settings read from
lvm.conf).

lvm_config_find_bool() can now be passed a NULL lvm context
in which case it will only create cmd->cft, check the config
setting asked for, and destroy the cmd.
This commit is contained in:
David Teigland 2016-05-17 11:54:13 -05:00
parent ba9b7b69d9
commit 7fd4119d24
3 changed files with 71 additions and 3 deletions
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43
lib/commands/toolcontext.c
View File

@ -1776,6 +1776,49 @@ bad:
return 0;
}
void destroy_config_context(struct cmd_context *cmd)
{
_destroy_config(cmd);
if (cmd->mem)
dm_pool_destroy(cmd->mem);
if (cmd->libmem)
dm_pool_destroy(cmd->libmem);
dm_free(cmd);
}
/*
* A "config context" is a very light weight toolcontext that
* is only used for reading config settings from lvm.conf.
*/
struct cmd_context *create_config_context(void)
{
struct cmd_context *cmd;
if (!(cmd = dm_zalloc(sizeof(*cmd))))
goto_out;
strcpy(cmd->system_dir, DEFAULT_SYS_DIR);
if (!_get_env_vars(cmd))
goto_out;
if (!(cmd->libmem = dm_pool_create("library", 4 * 1024)))
goto_out;
dm_list_init(&cmd->config_files);
if (!_init_lvm_conf(cmd))
goto_out;
return cmd;
out:
if (cmd)
destroy_config_context(cmd);
return NULL;
}
/* Entry point */
struct cmd_context *create_toolcontext(unsigned is_long_lived,
const char *system_dir,

8
lib/commands/toolcontext.h
View File

@ -218,6 +218,14 @@ int init_lvmcache_orphans(struct cmd_context *cmd);
int init_filters(struct cmd_context *cmd, unsigned load_persistent_cache);
int init_connections(struct cmd_context *cmd);
/*
* A config context is a very light weight cmd struct that
* is only used for reading config settings from lvm.conf,
* which are at cmd->cft.
*/
struct cmd_context *create_config_context(void);
void destroy_config_context(struct cmd_context *cmd);
struct format_type *get_format_by_name(struct cmd_context *cmd, const char *format);
const char *system_id_from_string(struct cmd_context *cmd, const char *str);

23
liblvm/lvm_base.c
View File

@ -126,14 +126,31 @@ int lvm_config_override(lvm_t libh, const char *config_settings)
return rc;
}
/*
* When full lvm connection is not being used, libh can be NULL
* and this command will internally create a single-use, light-weight
* cmd struct that only has cmd->cft populated from lvm.conf.
*/
int lvm_config_find_bool(lvm_t libh, const char *config_path, int fail)
{
int rc = 0;
struct cmd_context *cmd = (struct cmd_context *)libh;
struct saved_env e = store_user_env((struct cmd_context *)libh);
struct cmd_context *cmd;
struct saved_env e;
if (libh) {
cmd = (struct cmd_context *)libh;
e = store_user_env((struct cmd_context *)libh);
} else {
if (!(cmd = create_config_context()))
return 0;
}
rc = dm_config_tree_find_bool(cmd->cft, config_path, fail);
restore_user_env(&e);
if (libh)
restore_user_env(&e);
else
destroy_config_context(cmd);
return rc;
}