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[PATCH] elevator_t lifetime rules and sysfs fixes

This commit is contained in:
Al Viro 2006-03-18 18:35:43 -05:00
parent 1cc9be68eb
commit 3d1ab40f4c
5 changed files with 159 additions and 201 deletions

View File

@ -1709,11 +1709,6 @@ static int as_init_queue(request_queue_t *q, elevator_t *e)
/*
* sysfs parts below
*/
struct as_fs_entry {
struct attribute attr;
ssize_t (*show)(struct as_data *, char *);
ssize_t (*store)(struct as_data *, const char *, size_t);
};
static ssize_t
as_var_show(unsigned int var, char *page)
@ -1730,8 +1725,9 @@ as_var_store(unsigned long *var, const char *page, size_t count)
return count;
}
static ssize_t as_est_show(struct as_data *ad, char *page)
static ssize_t as_est_show(elevator_t *e, char *page)
{
struct as_data *ad = e->elevator_data;
int pos = 0;
pos += sprintf(page+pos, "%lu %% exit probability\n",
@ -1747,8 +1743,9 @@ static ssize_t as_est_show(struct as_data *ad, char *page)
}
#define SHOW_FUNCTION(__FUNC, __VAR) \
static ssize_t __FUNC(struct as_data *ad, char *page) \
static ssize_t __FUNC(elevator_t *e, char *page) \
{ \
struct as_data *ad = e->elevator_data; \
return as_var_show(jiffies_to_msecs((__VAR)), (page)); \
}
SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]);
@ -1759,9 +1756,10 @@ SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[REQ_ASYNC]);
#undef SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count) \
static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
{ \
int ret = as_var_store(__PTR, (page), count); \
struct as_data *ad = e->elevator_data; \
int ret = as_var_store(__PTR, (page), count); \
if (*(__PTR) < (MIN)) \
*(__PTR) = (MIN); \
else if (*(__PTR) > (MAX)) \
@ -1778,37 +1776,37 @@ STORE_FUNCTION(as_write_batchexpire_store,
&ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
#undef STORE_FUNCTION
static struct as_fs_entry as_est_entry = {
static struct elv_fs_entry as_est_entry = {
.attr = {.name = "est_time", .mode = S_IRUGO },
.show = as_est_show,
};
static struct as_fs_entry as_readexpire_entry = {
static struct elv_fs_entry as_readexpire_entry = {
.attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
.show = as_readexpire_show,
.store = as_readexpire_store,
};
static struct as_fs_entry as_writeexpire_entry = {
static struct elv_fs_entry as_writeexpire_entry = {
.attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
.show = as_writeexpire_show,
.store = as_writeexpire_store,
};
static struct as_fs_entry as_anticexpire_entry = {
static struct elv_fs_entry as_anticexpire_entry = {
.attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR },
.show = as_anticexpire_show,
.store = as_anticexpire_store,
};
static struct as_fs_entry as_read_batchexpire_entry = {
static struct elv_fs_entry as_read_batchexpire_entry = {
.attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR },
.show = as_read_batchexpire_show,
.store = as_read_batchexpire_store,
};
static struct as_fs_entry as_write_batchexpire_entry = {
static struct elv_fs_entry as_write_batchexpire_entry = {
.attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR },
.show = as_write_batchexpire_show,
.store = as_write_batchexpire_store,
};
static struct attribute *default_attrs[] = {
static struct attribute *as_attrs[] = {
&as_est_entry.attr,
&as_readexpire_entry.attr,
&as_writeexpire_entry.attr,
@ -1818,43 +1816,6 @@ static struct attribute *default_attrs[] = {
NULL,
};
#define to_as(atr) container_of((atr), struct as_fs_entry, attr)
static ssize_t
as_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct as_fs_entry *entry = to_as(attr);
if (!entry->show)
return -EIO;
return entry->show(e->elevator_data, page);
}
static ssize_t
as_attr_store(struct kobject *kobj, struct attribute *attr,
const char *page, size_t length)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct as_fs_entry *entry = to_as(attr);
if (!entry->store)
return -EIO;
return entry->store(e->elevator_data, page, length);
}
static struct sysfs_ops as_sysfs_ops = {
.show = as_attr_show,
.store = as_attr_store,
};
static struct kobj_type as_ktype = {
.sysfs_ops = &as_sysfs_ops,
.default_attrs = default_attrs,
};
static struct elevator_type iosched_as = {
.ops = {
.elevator_merge_fn = as_merge,
@ -1876,7 +1837,7 @@ static struct elevator_type iosched_as = {
.trim = as_trim,
},
.elevator_ktype = &as_ktype,
.elevator_attrs = as_attrs,
.elevator_name = "anticipatory",
.elevator_owner = THIS_MODULE,
};

View File

@ -2275,11 +2275,6 @@ fail:
/*
* sysfs parts below -->
*/
struct cfq_fs_entry {
struct attribute attr;
ssize_t (*show)(struct cfq_data *, char *);
ssize_t (*store)(struct cfq_data *, const char *, size_t);
};
static ssize_t
cfq_var_show(unsigned int var, char *page)
@ -2297,8 +2292,9 @@ cfq_var_store(unsigned int *var, const char *page, size_t count)
}
#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
static ssize_t __FUNC(struct cfq_data *cfqd, char *page) \
static ssize_t __FUNC(elevator_t *e, char *page) \
{ \
struct cfq_data *cfqd = e->elevator_data; \
unsigned int __data = __VAR; \
if (__CONV) \
__data = jiffies_to_msecs(__data); \
@ -2318,8 +2314,9 @@ SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0);
#undef SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count) \
static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
{ \
struct cfq_data *cfqd = e->elevator_data; \
unsigned int __data; \
int ret = cfq_var_store(&__data, (page), count); \
if (__data < (MIN)) \
@ -2345,63 +2342,63 @@ STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX,
STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0);
#undef STORE_FUNCTION
static struct cfq_fs_entry cfq_quantum_entry = {
static struct elv_fs_entry cfq_quantum_entry = {
.attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR },
.show = cfq_quantum_show,
.store = cfq_quantum_store,
};
static struct cfq_fs_entry cfq_queued_entry = {
static struct elv_fs_entry cfq_queued_entry = {
.attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR },
.show = cfq_queued_show,
.store = cfq_queued_store,
};
static struct cfq_fs_entry cfq_fifo_expire_sync_entry = {
static struct elv_fs_entry cfq_fifo_expire_sync_entry = {
.attr = {.name = "fifo_expire_sync", .mode = S_IRUGO | S_IWUSR },
.show = cfq_fifo_expire_sync_show,
.store = cfq_fifo_expire_sync_store,
};
static struct cfq_fs_entry cfq_fifo_expire_async_entry = {
static struct elv_fs_entry cfq_fifo_expire_async_entry = {
.attr = {.name = "fifo_expire_async", .mode = S_IRUGO | S_IWUSR },
.show = cfq_fifo_expire_async_show,
.store = cfq_fifo_expire_async_store,
};
static struct cfq_fs_entry cfq_back_max_entry = {
static struct elv_fs_entry cfq_back_max_entry = {
.attr = {.name = "back_seek_max", .mode = S_IRUGO | S_IWUSR },
.show = cfq_back_max_show,
.store = cfq_back_max_store,
};
static struct cfq_fs_entry cfq_back_penalty_entry = {
static struct elv_fs_entry cfq_back_penalty_entry = {
.attr = {.name = "back_seek_penalty", .mode = S_IRUGO | S_IWUSR },
.show = cfq_back_penalty_show,
.store = cfq_back_penalty_store,
};
static struct cfq_fs_entry cfq_slice_sync_entry = {
static struct elv_fs_entry cfq_slice_sync_entry = {
.attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
.show = cfq_slice_sync_show,
.store = cfq_slice_sync_store,
};
static struct cfq_fs_entry cfq_slice_async_entry = {
static struct elv_fs_entry cfq_slice_async_entry = {
.attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
.show = cfq_slice_async_show,
.store = cfq_slice_async_store,
};
static struct cfq_fs_entry cfq_slice_async_rq_entry = {
static struct elv_fs_entry cfq_slice_async_rq_entry = {
.attr = {.name = "slice_async_rq", .mode = S_IRUGO | S_IWUSR },
.show = cfq_slice_async_rq_show,
.store = cfq_slice_async_rq_store,
};
static struct cfq_fs_entry cfq_slice_idle_entry = {
static struct elv_fs_entry cfq_slice_idle_entry = {
.attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
.show = cfq_slice_idle_show,
.store = cfq_slice_idle_store,
};
static struct cfq_fs_entry cfq_max_depth_entry = {
static struct elv_fs_entry cfq_max_depth_entry = {
.attr = {.name = "max_depth", .mode = S_IRUGO | S_IWUSR },
.show = cfq_max_depth_show,
.store = cfq_max_depth_store,
};
static struct attribute *default_attrs[] = {
static struct attribute *cfq_attrs[] = {
&cfq_quantum_entry.attr,
&cfq_queued_entry.attr,
&cfq_fifo_expire_sync_entry.attr,
@ -2416,43 +2413,6 @@ static struct attribute *default_attrs[] = {
NULL,
};
#define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr)
static ssize_t
cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct cfq_fs_entry *entry = to_cfq(attr);
if (!entry->show)
return -EIO;
return entry->show(e->elevator_data, page);
}
static ssize_t
cfq_attr_store(struct kobject *kobj, struct attribute *attr,
const char *page, size_t length)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct cfq_fs_entry *entry = to_cfq(attr);
if (!entry->store)
return -EIO;
return entry->store(e->elevator_data, page, length);
}
static struct sysfs_ops cfq_sysfs_ops = {
.show = cfq_attr_show,
.store = cfq_attr_store,
};
static struct kobj_type cfq_ktype = {
.sysfs_ops = &cfq_sysfs_ops,
.default_attrs = default_attrs,
};
static struct elevator_type iosched_cfq = {
.ops = {
.elevator_merge_fn = cfq_merge,
@ -2473,7 +2433,7 @@ static struct elevator_type iosched_cfq = {
.elevator_exit_fn = cfq_exit_queue,
.trim = cfq_trim,
},
.elevator_ktype = &cfq_ktype,
.elevator_attrs = cfq_attrs,
.elevator_name = "cfq",
.elevator_owner = THIS_MODULE,
};

View File

@ -694,11 +694,6 @@ deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
/*
* sysfs parts below
*/
struct deadline_fs_entry {
struct attribute attr;
ssize_t (*show)(struct deadline_data *, char *);
ssize_t (*store)(struct deadline_data *, const char *, size_t);
};
static ssize_t
deadline_var_show(int var, char *page)
@ -716,9 +711,10 @@ deadline_var_store(int *var, const char *page, size_t count)
}
#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
static ssize_t __FUNC(struct deadline_data *dd, char *page) \
static ssize_t __FUNC(elevator_t *e, char *page) \
{ \
int __data = __VAR; \
struct deadline_data *dd = e->elevator_data; \
int __data = __VAR; \
if (__CONV) \
__data = jiffies_to_msecs(__data); \
return deadline_var_show(__data, (page)); \
@ -731,8 +727,9 @@ SHOW_FUNCTION(deadline_fifobatch_show, dd->fifo_batch, 0);
#undef SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
static ssize_t __FUNC(struct deadline_data *dd, const char *page, size_t count) \
static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
{ \
struct deadline_data *dd = e->elevator_data; \
int __data; \
int ret = deadline_var_store(&__data, (page), count); \
if (__data < (MIN)) \
@ -752,33 +749,33 @@ STORE_FUNCTION(deadline_frontmerges_store, &dd->front_merges, 0, 1, 0);
STORE_FUNCTION(deadline_fifobatch_store, &dd->fifo_batch, 0, INT_MAX, 0);
#undef STORE_FUNCTION
static struct deadline_fs_entry deadline_readexpire_entry = {
static struct elv_fs_entry deadline_readexpire_entry = {
.attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
.show = deadline_readexpire_show,
.store = deadline_readexpire_store,
};
static struct deadline_fs_entry deadline_writeexpire_entry = {
static struct elv_fs_entry deadline_writeexpire_entry = {
.attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
.show = deadline_writeexpire_show,
.store = deadline_writeexpire_store,
};
static struct deadline_fs_entry deadline_writesstarved_entry = {
static struct elv_fs_entry deadline_writesstarved_entry = {
.attr = {.name = "writes_starved", .mode = S_IRUGO | S_IWUSR },
.show = deadline_writesstarved_show,
.store = deadline_writesstarved_store,
};
static struct deadline_fs_entry deadline_frontmerges_entry = {
static struct elv_fs_entry deadline_frontmerges_entry = {
.attr = {.name = "front_merges", .mode = S_IRUGO | S_IWUSR },
.show = deadline_frontmerges_show,
.store = deadline_frontmerges_store,
};
static struct deadline_fs_entry deadline_fifobatch_entry = {
static struct elv_fs_entry deadline_fifobatch_entry = {
.attr = {.name = "fifo_batch", .mode = S_IRUGO | S_IWUSR },
.show = deadline_fifobatch_show,
.store = deadline_fifobatch_store,
};
static struct attribute *default_attrs[] = {
static struct attribute *deadline_attrs[] = {
&deadline_readexpire_entry.attr,
&deadline_writeexpire_entry.attr,
&deadline_writesstarved_entry.attr,
@ -787,43 +784,6 @@ static struct attribute *default_attrs[] = {
NULL,
};
#define to_deadline(atr) container_of((atr), struct deadline_fs_entry, attr)
static ssize_t
deadline_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct deadline_fs_entry *entry = to_deadline(attr);
if (!entry->show)
return -EIO;
return entry->show(e->elevator_data, page);
}
static ssize_t
deadline_attr_store(struct kobject *kobj, struct attribute *attr,
const char *page, size_t length)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct deadline_fs_entry *entry = to_deadline(attr);
if (!entry->store)
return -EIO;
return entry->store(e->elevator_data, page, length);
}
static struct sysfs_ops deadline_sysfs_ops = {
.show = deadline_attr_show,
.store = deadline_attr_store,
};
static struct kobj_type deadline_ktype = {
.sysfs_ops = &deadline_sysfs_ops,
.default_attrs = default_attrs,
};
static struct elevator_type iosched_deadline = {
.ops = {
.elevator_merge_fn = deadline_merge,
@ -840,7 +800,7 @@ static struct elevator_type iosched_deadline = {
.elevator_exit_fn = deadline_exit_queue,
},
.elevator_ktype = &deadline_ktype,
.elevator_attrs = deadline_attrs,
.elevator_name = "deadline",
.elevator_owner = THIS_MODULE,
};

View File

@ -120,15 +120,10 @@ static struct elevator_type *elevator_get(const char *name)
return e;
}
static int elevator_attach(request_queue_t *q, struct elevator_type *e,
struct elevator_queue *eq)
static int elevator_attach(request_queue_t *q, struct elevator_queue *eq)
{
int ret = 0;
memset(eq, 0, sizeof(*eq));
eq->ops = &e->ops;
eq->elevator_type = e;
q->elevator = eq;
if (eq->ops->elevator_init_fn)
@ -154,6 +149,32 @@ static int __init elevator_setup(char *str)
__setup("elevator=", elevator_setup);
static struct kobj_type elv_ktype;
static elevator_t *elevator_alloc(struct elevator_type *e)
{
elevator_t *eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
if (eq) {
memset(eq, 0, sizeof(*eq));
eq->ops = &e->ops;
eq->elevator_type = e;
kobject_init(&eq->kobj);
snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
eq->kobj.ktype = &elv_ktype;
mutex_init(&eq->sysfs_lock);
} else {
elevator_put(e);
}
return eq;
}
static void elevator_release(struct kobject *kobj)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
elevator_put(e->elevator_type);
kfree(e);
}
int elevator_init(request_queue_t *q, char *name)
{
struct elevator_type *e = NULL;
@ -176,29 +197,26 @@ int elevator_init(request_queue_t *q, char *name)
e = elevator_get("noop");
}
eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
if (!eq) {
elevator_put(e);
eq = elevator_alloc(e);
if (!eq)
return -ENOMEM;
}
ret = elevator_attach(q, e, eq);
if (ret) {
kfree(eq);
elevator_put(e);
}
ret = elevator_attach(q, eq);
if (ret)
kobject_put(&eq->kobj);
return ret;
}
void elevator_exit(elevator_t *e)
{
mutex_lock(&e->sysfs_lock);
if (e->ops->elevator_exit_fn)
e->ops->elevator_exit_fn(e);
e->ops = NULL;
mutex_unlock(&e->sysfs_lock);
elevator_put(e->elevator_type);
e->elevator_type = NULL;
kfree(e);
kobject_put(&e->kobj);
}
/*
@ -627,26 +645,78 @@ void elv_completed_request(request_queue_t *q, struct request *rq)
}
}
#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
static ssize_t
elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct elv_fs_entry *entry = to_elv(attr);
ssize_t error;
if (!entry->show)
return -EIO;
mutex_lock(&e->sysfs_lock);
error = e->ops ? entry->show(e, page) : -ENOENT;
mutex_unlock(&e->sysfs_lock);
return error;
}
static ssize_t
elv_attr_store(struct kobject *kobj, struct attribute *attr,
const char *page, size_t length)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct elv_fs_entry *entry = to_elv(attr);
ssize_t error;
if (!entry->store)
return -EIO;
mutex_lock(&e->sysfs_lock);
error = e->ops ? entry->store(e, page, length) : -ENOENT;
mutex_unlock(&e->sysfs_lock);
return error;
}
static struct sysfs_ops elv_sysfs_ops = {
.show = elv_attr_show,
.store = elv_attr_store,
};
static struct kobj_type elv_ktype = {
.sysfs_ops = &elv_sysfs_ops,
.release = elevator_release,
};
int elv_register_queue(struct request_queue *q)
{
elevator_t *e = q->elevator;
int error;
e->kobj.parent = kobject_get(&q->kobj);
if (!e->kobj.parent)
return -EBUSY;
e->kobj.parent = &q->kobj;
snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
e->kobj.ktype = e->elevator_type->elevator_ktype;
return kobject_register(&e->kobj);
error = kobject_add(&e->kobj);
if (!error) {
struct attribute **attr = e->elevator_type->elevator_attrs;
if (attr) {
while (*attr) {
if (sysfs_create_file(&e->kobj,*attr++))
break;
}
}
kobject_uevent(&e->kobj, KOBJ_ADD);
}
return error;
}
void elv_unregister_queue(struct request_queue *q)
{
if (q) {
elevator_t *e = q->elevator;
kobject_unregister(&e->kobj);
kobject_put(&q->kobj);
kobject_uevent(&e->kobj, KOBJ_REMOVE);
kobject_del(&e->kobj);
}
}
@ -697,16 +767,16 @@ EXPORT_SYMBOL_GPL(elv_unregister);
* need for the new one. this way we have a chance of going back to the old
* one, if the new one fails init for some reason.
*/
static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
{
elevator_t *old_elevator, *e;
/*
* Allocate new elevator
*/
e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
e = elevator_alloc(new_e);
if (!e)
goto error;
return 0;
/*
* Turn on BYPASS and drain all requests w/ elevator private data
@ -737,7 +807,7 @@ static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
/*
* attach and start new elevator
*/
if (elevator_attach(q, new_e, e))
if (elevator_attach(q, e))
goto fail;
if (elv_register_queue(q))
@ -748,7 +818,7 @@ static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
*/
elevator_exit(old_elevator);
clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
return;
return 1;
fail_register:
/*
@ -761,10 +831,9 @@ fail:
q->elevator = old_elevator;
elv_register_queue(q);
clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
kfree(e);
error:
elevator_put(new_e);
printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
if (e)
kobject_put(&e->kobj);
return 0;
}
ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
@ -791,7 +860,8 @@ ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
return count;
}
elevator_switch(q, e);
if (!elevator_switch(q, e))
printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
return count;
}

View File

@ -61,7 +61,7 @@ struct elevator_type
struct list_head list;
struct elevator_ops ops;
struct elevator_type *elevator_type;
struct kobj_type *elevator_ktype;
struct attribute **elevator_attrs;
char elevator_name[ELV_NAME_MAX];
struct module *elevator_owner;
};
@ -75,6 +75,7 @@ struct elevator_queue
void *elevator_data;
struct kobject kobj;
struct elevator_type *elevator_type;
struct mutex sysfs_lock;
};
/*
@ -141,6 +142,12 @@ enum {
ELV_MQUEUE_MUST,
};
struct elv_fs_entry {
struct attribute attr;
ssize_t (*show)(elevator_t *, char *);
ssize_t (*store)(elevator_t *, const char *, size_t);
};
#define rq_end_sector(rq) ((rq)->sector + (rq)->nr_sectors)
#endif