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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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#include "dm.h"#include "dm-path-selector.h"
#include <linux/slab.h>#include <linux/ctype.h>#include <linux/errno.h>#include <linux/module.h>#include <linux/atomic.h>
#define DM_MSG_PREFIX "multipath queue-length"#define QL_MIN_IO 1#define QL_VERSION "0.2.0"
struct selector { struct list_head valid_paths; struct list_head failed_paths; spinlock_t lock;};
struct path_info { struct list_head list; struct dm_path *path; unsigned int repeat_count; atomic_t qlen; /* the number of in-flight I/Os */};
static struct selector *alloc_selector(void){ struct selector *s = kmalloc_obj(*s);
if (s) { INIT_LIST_HEAD(&s->valid_paths); INIT_LIST_HEAD(&s->failed_paths); spin_lock_init(&s->lock); }
return s;}
static int ql_create(struct path_selector *ps, unsigned int argc, char **argv){ struct selector *s = alloc_selector();
if (!s) return -ENOMEM;
ps->context = s; return 0;}
static void ql_free_paths(struct list_head *paths){ struct path_info *pi, *next;
list_for_each_entry_safe(pi, next, paths, list) { list_del(&pi->list); kfree(pi); }}
static void ql_destroy(struct path_selector *ps){ struct selector *s = ps->context;
ql_free_paths(&s->valid_paths); ql_free_paths(&s->failed_paths); kfree(s); ps->context = NULL;}
static int ql_status(struct path_selector *ps, struct dm_path *path, status_type_t type, char *result, unsigned int maxlen){ unsigned int sz = 0; struct path_info *pi;
/* When called with NULL path, return selector status/args. */ if (!path) DMEMIT("0 "); else { pi = path->pscontext;
switch (type) { case STATUSTYPE_INFO: DMEMIT("%d ", atomic_read(&pi->qlen)); break; case STATUSTYPE_TABLE: DMEMIT("%u ", pi->repeat_count); break; case STATUSTYPE_IMA: *result = '\0'; break; } }
return sz;}
static int ql_add_path(struct path_selector *ps, struct dm_path *path, int argc, char **argv, char **error){ struct selector *s = ps->context; struct path_info *pi; unsigned int repeat_count = QL_MIN_IO; char dummy; unsigned long flags;
/* * Arguments: [<repeat_count>] * <repeat_count>: The number of I/Os before switching path. * If not given, default (QL_MIN_IO) is used. */ if (argc > 1) { *error = "queue-length ps: incorrect number of arguments"; return -EINVAL; }
if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) { *error = "queue-length ps: invalid repeat count"; return -EINVAL; }
if (repeat_count > 1) { DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead"); repeat_count = 1; }
/* Allocate the path information structure */ pi = kmalloc_obj(*pi); if (!pi) { *error = "queue-length ps: Error allocating path information"; return -ENOMEM; }
pi->path = path; pi->repeat_count = repeat_count; atomic_set(&pi->qlen, 0);
path->pscontext = pi;
spin_lock_irqsave(&s->lock, flags); list_add_tail(&pi->list, &s->valid_paths); spin_unlock_irqrestore(&s->lock, flags);
return 0;}
static void ql_fail_path(struct path_selector *ps, struct dm_path *path){ struct selector *s = ps->context; struct path_info *pi = path->pscontext; unsigned long flags;
spin_lock_irqsave(&s->lock, flags); list_move(&pi->list, &s->failed_paths); spin_unlock_irqrestore(&s->lock, flags);}
static int ql_reinstate_path(struct path_selector *ps, struct dm_path *path){ struct selector *s = ps->context; struct path_info *pi = path->pscontext; unsigned long flags;
spin_lock_irqsave(&s->lock, flags); list_move_tail(&pi->list, &s->valid_paths); spin_unlock_irqrestore(&s->lock, flags);
return 0;}
/* * Select a path having the minimum number of in-flight I/Os */static struct dm_path *ql_select_path(struct path_selector *ps, size_t nr_bytes){ struct selector *s = ps->context; struct path_info *pi = NULL, *best = NULL; struct dm_path *ret = NULL; unsigned long flags;
spin_lock_irqsave(&s->lock, flags); if (list_empty(&s->valid_paths)) goto out;
list_for_each_entry(pi, &s->valid_paths, list) { if (!best || (atomic_read(&pi->qlen) < atomic_read(&best->qlen))) best = pi;
if (!atomic_read(&best->qlen)) break; }
if (!best) goto out;
/* Move most recently used to least preferred to evenly balance. */ list_move_tail(&best->list, &s->valid_paths);
ret = best->path;out: spin_unlock_irqrestore(&s->lock, flags); return ret;}
static int ql_start_io(struct path_selector *ps, struct dm_path *path, size_t nr_bytes){ struct path_info *pi = path->pscontext;
atomic_inc(&pi->qlen);
return 0;}
static int ql_end_io(struct path_selector *ps, struct dm_path *path, size_t nr_bytes, u64 start_time){ struct path_info *pi = path->pscontext;
atomic_dec(&pi->qlen);
return 0;}
static struct path_selector_type ql_ps = { .name = "queue-length", .module = THIS_MODULE, .table_args = 1, .info_args = 1, .create = ql_create, .destroy = ql_destroy, .status = ql_status, .add_path = ql_add_path, .fail_path = ql_fail_path, .reinstate_path = ql_reinstate_path, .select_path = ql_select_path, .start_io = ql_start_io, .end_io = ql_end_io,};
static int __init dm_ql_init(void){ int r = dm_register_path_selector(&ql_ps);
if (r < 0) { DMERR("register failed %d", r); return r; }
DMINFO("version " QL_VERSION " loaded");
return r;}
static void __exit dm_ql_exit(void){ dm_unregister_path_selector(&ql_ps);}
module_init(dm_ql_init);module_exit(dm_ql_exit);
MODULE_AUTHOR("Stefan Bader <Stefan.Bader at de.ibm.com>");MODULE_DESCRIPTION( "(C) Copyright IBM Corp. 2004,2005 All Rights Reserved.\n" DM_NAME " path selector to balance the number of in-flight I/Os");MODULE_LICENSE("GPL");