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zvol: reduce linear list search
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Use kernel ida to generate minor number, and use hash table to find zvol with
name.

Signed-off-by: Chunwei Chen <[email protected]>
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Chunwei Chen committed Nov 30, 2016
1 parent 63d9fd8 commit 0a7c4b7
Showing 1 changed file with 65 additions and 52 deletions.
117 changes: 65 additions & 52 deletions module/zfs/zvol.c
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,11 @@ static kmutex_t zvol_state_lock;
static list_t zvol_state_list;
void *zvol_tag = "zvol_tag";

#define ZVOL_HT_SIZE 1024
static struct hlist_head *zvol_htable;
#define ZVOL_HT_HEAD(hash) (&zvol_htable[(hash) & (ZVOL_HT_SIZE-1)])
static DEFINE_IDA(zvol_ida);

/*
* The in-core state of each volume.
*/
Expand All @@ -81,6 +86,8 @@ typedef struct zvol_state {
struct gendisk *zv_disk; /* generic disk */
struct request_queue *zv_queue; /* request queue */
list_node_t zv_next; /* next zvol_state_t linkage */
uint64_t zv_hash; /* name hash */
struct hlist_node zv_hlink; /* hash link */
} zvol_state_t;

typedef enum {
Expand All @@ -102,30 +109,17 @@ typedef struct {

#define ZVOL_RDONLY 0x1

/*
* Find the next available range of ZVOL_MINORS minor numbers. The
* zvol_state_list is kept in ascending minor order so we simply need
* to scan the list for the first gap in the sequence. This allows us
* to recycle minor number as devices are created and removed.
*/
static int
zvol_find_minor(unsigned *minor)
static uint64_t
zvol_name_hash(const char *name)
{
zvol_state_t *zv;

*minor = 0;
ASSERT(MUTEX_HELD(&zvol_state_lock));
for (zv = list_head(&zvol_state_list); zv != NULL;
zv = list_next(&zvol_state_list, zv), *minor += ZVOL_MINORS) {
if (MINOR(zv->zv_dev) != MINOR(*minor))
break;
int i;
uint64_t crc = -1ULL;
uint8_t *p = (uint8_t *)name;
ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
for (i = 0; i < MAXNAMELEN - 1 && *p; i++, p++) {
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (*p)) & 0xFF];
}

/* All minors are in use */
if (*minor >= (1 << MINORBITS))
return (SET_ERROR(ENXIO));

return (0);
return (crc);
}

/*
Expand All @@ -146,24 +140,33 @@ zvol_find_by_dev(dev_t dev)
return (NULL);
}

/*
* Find a zvol_state_t given the name provided at zvol_alloc() time.
*/
static zvol_state_t *
zvol_find_by_name(const char *name)
zvol_find_by_name_hash(const char *name, uint64_t hash)
{
zvol_state_t *zv;
struct hlist_node *p;

ASSERT(MUTEX_HELD(&zvol_state_lock));
for (zv = list_head(&zvol_state_list); zv != NULL;
zv = list_next(&zvol_state_list, zv)) {
if (strncmp(zv->zv_name, name, MAXNAMELEN) == 0)
hlist_for_each(p, ZVOL_HT_HEAD(hash)) {
zv = hlist_entry(p, zvol_state_t, zv_hlink);
if (zv->zv_hash == hash &&
strncmp(zv->zv_name, name, MAXNAMELEN) == 0)
return (zv);
}

return (NULL);
}

/*
* Find a zvol_state_t given the name provided at zvol_alloc() time.
*/
static zvol_state_t *
zvol_find_by_name(const char *name)
{
uint64_t hash = zvol_name_hash(name);

return (zvol_find_by_name_hash(name, hash));
}


/*
* Given a path, return TRUE if path is a ZVOL.
Expand Down Expand Up @@ -921,32 +924,24 @@ zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio)
}

/*
* The zvol_state_t's are inserted in increasing MINOR(dev_t) order.
* The zvol_state_t's are inserted into zvol_state_list and zvol_htable.
*/
static void
zvol_insert(zvol_state_t *zv_insert)
zvol_insert(zvol_state_t *zv)
{
zvol_state_t *zv = NULL;

ASSERT(MUTEX_HELD(&zvol_state_lock));
ASSERT3U(MINOR(zv_insert->zv_dev) & ZVOL_MINOR_MASK, ==, 0);
for (zv = list_head(&zvol_state_list); zv != NULL;
zv = list_next(&zvol_state_list, zv)) {
if (MINOR(zv->zv_dev) > MINOR(zv_insert->zv_dev))
break;
}

list_insert_before(&zvol_state_list, zv, zv_insert);
list_insert_head(&zvol_state_list, zv);
hlist_add_head(&zv->zv_hlink, ZVOL_HT_HEAD(zv->zv_hash));
}

/*
* Simply remove the zvol from to list of zvols.
*/
static void
zvol_remove(zvol_state_t *zv_remove)
zvol_remove(zvol_state_t *zv)
{
ASSERT(MUTEX_HELD(&zvol_state_lock));
list_remove(&zvol_state_list, zv_remove);
list_remove(&zvol_state_list, zv);
hlist_del(&zv->zv_hlink);
}

static int
Expand Down Expand Up @@ -1334,6 +1329,7 @@ zvol_free(zvol_state_t *zv)
blk_cleanup_queue(zv->zv_queue);
put_disk(zv->zv_disk);

ida_simple_remove(&zvol_ida, MINOR(zv->zv_dev) >> ZVOL_MINOR_BITS);
kmem_free(zv, sizeof (zvol_state_t));
}

Expand All @@ -1352,10 +1348,17 @@ zvol_create_minor_impl(const char *name)
uint64_t len;
unsigned minor = 0;
int error = 0;
int idx;
uint64_t hash = zvol_name_hash(name);

idx = ida_simple_get(&zvol_ida, 0, 0, kmem_flags_convert(KM_SLEEP));
if (idx < 0)
return (SET_ERROR(-idx));
minor = idx << ZVOL_MINOR_BITS;

mutex_enter(&zvol_state_lock);

zv = zvol_find_by_name(name);
zv = zvol_find_by_name_hash(name, hash);
if (zv) {
error = SET_ERROR(EEXIST);
goto out;
Expand All @@ -1375,15 +1378,12 @@ zvol_create_minor_impl(const char *name)
if (error)
goto out_dmu_objset_disown;

error = zvol_find_minor(&minor);
if (error)
goto out_dmu_objset_disown;

zv = zvol_alloc(MKDEV(zvol_major, minor), name);
if (zv == NULL) {
error = SET_ERROR(EAGAIN);
goto out_dmu_objset_disown;
}
zv->zv_hash = hash;

if (dmu_objset_is_snapshot(os))
zv->zv_flags |= ZVOL_RDONLY;
Expand Down Expand Up @@ -1449,6 +1449,7 @@ zvol_create_minor_impl(const char *name)
add_disk(zv->zv_disk);
} else {
mutex_exit(&zvol_state_lock);
ida_simple_remove(&zvol_ida, idx);
}

return (SET_ERROR(error));
Expand Down Expand Up @@ -1933,23 +1934,34 @@ zvol_rename_minors(spa_t *spa, const char *name1, const char *name2,
int
zvol_init(void)
{
int error;
int i, error;

list_create(&zvol_state_list, sizeof (zvol_state_t),
offsetof(zvol_state_t, zv_next));
mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL);

zvol_htable = kmem_alloc(ZVOL_HT_SIZE * sizeof (struct hlist_head),
KM_SLEEP);
if (!zvol_htable) {
error = ENOMEM;
goto out;
}
for (i = 0; i < ZVOL_HT_SIZE; i++)
INIT_HLIST_HEAD(&zvol_htable[i]);

error = register_blkdev(zvol_major, ZVOL_DRIVER);
if (error) {
printk(KERN_INFO "ZFS: register_blkdev() failed %d\n", error);
goto out;
goto out_free;
}

blk_register_region(MKDEV(zvol_major, 0), 1UL << MINORBITS,
THIS_MODULE, zvol_probe, NULL, NULL);

return (0);

out_free:
kmem_free(zvol_htable, ZVOL_HT_SIZE * sizeof (struct hlist_head));
out:
mutex_destroy(&zvol_state_lock);
list_destroy(&zvol_state_list);
Expand All @@ -1964,6 +1976,7 @@ zvol_fini(void)

blk_unregister_region(MKDEV(zvol_major, 0), 1UL << MINORBITS);
unregister_blkdev(zvol_major, ZVOL_DRIVER);
kmem_free(zvol_htable, ZVOL_HT_SIZE * sizeof (struct hlist_head));

list_destroy(&zvol_state_list);
mutex_destroy(&zvol_state_lock);
Expand Down

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