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device_mapper: add dm_device_list_find_by_dev

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Introduce function to find device's name and uuid for
a given major:minor.

This information is cached with dm_device_list which reads all the
info from single ioctl(DM_DEVICE_LIST).
Lvm keeps major:minor name & uuid for active devices in the system.
This commit is contained in:
Zdenek Kabelac 2024-05-27 15:34:16 +02:00
parent 5c24d6d4db
commit 36691b9844
2 changed files with 80 additions and 5 deletions
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7
device_mapper/all.h
View File

@ -175,8 +175,8 @@ struct dm_names {
struct dm_active_device {
struct dm_list list;
int major;
int minor;
uint32_t major;
uint32_t minor;
char *name; /* device name */
uint32_t event_nr; /* valid when DM_DEVICE_LIST_HAS_EVENT_NR is set */
@ -237,6 +237,9 @@ int dm_task_get_device_list(struct dm_task *dmt, struct dm_list **devs_list,
*/
int dm_device_list_find_by_uuid(struct dm_list *devs_list, const char *uuid,
const struct dm_active_device **dev);
int dm_device_list_find_by_dev(const struct dm_list *devs_list,
uint32_t major, uint32_t minor,
const char **name, const char **uuid);
/* Release all associated memory with list of active DM devices */
void dm_device_list_destroy(struct dm_list **devs_list);

78
device_mapper/ioctl/libdm-iface.c
View File

@ -787,8 +787,29 @@ struct dm_device_list {
unsigned count;
unsigned features;
struct dm_hash_table *uuids;
/* As last element (sized according to count), pointers to individual dm_devs */
struct dm_active_device *sorted[]; /* For bsearch() devs sorted by device node */
};
/*
* Comparing 2 dev nodes by its minor.
*
* TODO: enhance if DM would ever use multiple major:minor...
*/
static int _dm_dev_compare(const void *p1, const void *p2)
{
int m1 = (*(struct dm_active_device **)p1)->minor;
int m2 = (*(struct dm_active_device **)p2)->minor;
if (m1 > m2)
return 1;
if (m1 < m2)
return -1;
return 0;
}
int dm_task_get_device_list(struct dm_task *dmt, struct dm_list **devs_list,
unsigned *devs_features)
{
@ -800,6 +821,7 @@ int dm_task_get_device_list(struct dm_task *dmt, struct dm_list **devs_list,
char *uuid_ptr;
size_t len;
int cnt = 0;
unsigned index = 0;
*devs_list = 0;
*devs_features = 0;
@ -815,7 +837,9 @@ int dm_task_get_device_list(struct dm_task *dmt, struct dm_list **devs_list,
} while (next);
}
if (!(devs = malloc(sizeof(*devs) + (cnt ? cnt * sizeof(*dm_dev) + (char*)names1 - (char*)names + 256 : 0))))
/* buffer for devs + sorted ptrs + dm_devs + aligned strings */
if (!(devs = malloc(sizeof(*devs) + cnt * (2 * sizeof(void*) + sizeof(*dm_dev)) +
(char*)names1 - (char*)names + 256)))
return_0;
dm_list_init(&devs->list);
@ -828,11 +852,13 @@ int dm_task_get_device_list(struct dm_task *dmt, struct dm_list **devs_list,
goto out; /* nothing else to do */
}
dm_dev = (struct dm_active_device *) (devs + 1);
/* Shift position where to store individual dm_devs */
dm_dev = (struct dm_active_device *) ((long*) (devs + 1) + cnt);
do {
names = (struct dm_names *)((char *) names + next);
devs->sorted[index++] = dm_dev;
dm_dev->major = MAJOR(names->dev);
dm_dev->minor = MINOR(names->dev);
dm_dev->name = (char*)(dm_dev + 1);
@ -864,7 +890,7 @@ int dm_task_get_device_list(struct dm_task *dmt, struct dm_list **devs_list,
if (!dm_hash_insert(devs->uuids, dm_dev->uuid, dm_dev))
return_0; // FIXME
#if 0
log_debug("Active %s (%s) %d:%d event:%u",
log_debug("Active %s (%s) %u:%u event:%u",
dm_dev->name, dm_dev->uuid,
dm_dev->major, dm_dev->minor, dm_dev->event_nr);
#endif
@ -879,6 +905,15 @@ int dm_task_get_device_list(struct dm_task *dmt, struct dm_list **devs_list,
out:
*devs_list = (struct dm_list *)devs;
/* sort by minors */
qsort(devs->sorted, devs->count, sizeof(void*), _dm_dev_compare);
#if 0
for (int i = 0; i < index; ++i) /* check order */
log_debug("DM devices: minor=%d name=%s uuid=%s",
devs->sorted[i]->minor, devs->sorted[i]->name,
devs->sorted[i]->uuid);
#endif
return 1;
}
@ -898,6 +933,43 @@ int dm_device_list_find_by_uuid(struct dm_list *devs_list, const char *uuid,
return 0;
}
/*
* Find DM device in devs array for given major:minor.
* ATM assuming all DM devices use the single known major.
*
* NOTE:
* When major:minor is found, the 'name' and 'uuid' pointers
* are return as const string pointing to devs structure.
* Once the dm_device_list structure is destroyed
* those pointers become invalid!
*/
int dm_device_list_find_by_dev(const struct dm_list *devs_list,
uint32_t major, uint32_t minor,
const char **name, const char **uuid)
{
const struct dm_device_list *devs = (const struct dm_device_list *) devs_list;
const struct dm_active_device search = { .major = major, .minor = minor };
const struct dm_active_device *findme[] = { &search };
const struct dm_active_device **dm_dev_found;
const char *fname = NULL, *fuuid = NULL;
int ret = 0;
/* Prefer bsearch O(logN) over linear list scanning O(N) */
if ((dm_dev_found = bsearch(findme, devs->sorted, devs->count, sizeof(void*),
_dm_dev_compare))) {
fname = (*dm_dev_found)->name;
fuuid = (*dm_dev_found)->uuid;
ret = 1;
}
if (name)
*name = fname;
if (uuid)
*uuid = fuuid;
return ret;
}
void dm_device_list_destroy(struct dm_list **devs_list)
{
struct dm_device_list *devs = (struct dm_device_list *) *devs_list;