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freebsd-skq/sys/geom/geom.h
avg ee6ae8018d g_access: deal with races created by geoms that drop the topology lock 
The problem is that g_access() must be called with the GEOM topology
lock held.  And that gives a false impression that the lock is indeed
held across the call.  But this isn't always true because many classes,
ZVOL being one of the many, need to drop the lock.  It's either to
perform an I/O on the first open or to acquire a different lock (like in
g_mirror_access).

That, of course, can break many assumptions.  For example,
g_slice_access() adds an extra exclusive count on the first open. As
described above, an underlying geom may drop the topology lock and that
would open a race with another thread that would also request another
extra exclusive count.  In general, two consumers may be granted
incompatible accesses.

To avoid this problem the code is changed to mark a geom with special
flag before calling its access method and clear the flag afterwards.  If
another thread sees that flag, then it means that the topology lock has
been dropped (either by the geom in question or downstream from it), so
it is not safe to make another access call.  So, the second thread would
use g_topology_sleep() to wait until the flag is cleared and only then
would it proceed with the access.

Also see http://docs.freebsd.org/cgi/mid.cgi?809d9254-ee56-59d8-69a4-08838e985cea

PR:		225960
Reported by:	asomers
Reviewed by:	markj, mav
MFC after:	3 weeks
Differential Revision: https://reviews.freebsd.org/D14533
2018-03-15 09:16:10 +00:00

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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2002 Poul-Henning Kamp
* Copyright (c) 2002 Networks Associates Technology, Inc.
* All rights reserved.
*
* This software was developed for the FreeBSD Project by Poul-Henning Kamp
* and NAI Labs, the Security Research Division of Network Associates, Inc.
* under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
* DARPA CHATS research program.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The names of the authors may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _GEOM_GEOM_H_
#define _GEOM_GEOM_H_
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/sx.h>
#include <sys/queue.h>
#include <sys/ioccom.h>
#include <sys/conf.h>
#include <sys/module.h>
struct g_class;
struct g_geom;
struct g_consumer;
struct g_provider;
struct g_stat;
struct thread;
struct bio;
struct sbuf;
struct gctl_req;
struct g_configargs;
struct disk_zone_args;
typedef int g_config_t (struct g_configargs *ca);
typedef void g_ctl_req_t (struct gctl_req *, struct g_class *cp, char const *verb);
typedef int g_ctl_create_geom_t (struct gctl_req *, struct g_class *cp, struct g_provider *pp);
typedef int g_ctl_destroy_geom_t (struct gctl_req *, struct g_class *cp, struct g_geom *gp);
typedef int g_ctl_config_geom_t (struct gctl_req *, struct g_geom *gp, const char *verb);
typedef void g_init_t (struct g_class *mp);
typedef void g_fini_t (struct g_class *mp);
typedef struct g_geom * g_taste_t (struct g_class *, struct g_provider *, int flags);
typedef int g_ioctl_t(struct g_provider *pp, u_long cmd, void *data, int fflag, struct thread *td);
#define G_TF_NORMAL 0
#define G_TF_INSIST 1
#define G_TF_TRANSPARENT 2
typedef int g_access_t (struct g_provider *, int, int, int);
/* XXX: not sure about the thread arg */
typedef void g_orphan_t (struct g_consumer *);
typedef void g_start_t (struct bio *);
typedef void g_spoiled_t (struct g_consumer *);
typedef void g_attrchanged_t (struct g_consumer *, const char *attr);
typedef void g_provgone_t (struct g_provider *);
typedef void g_dumpconf_t (struct sbuf *, const char *indent, struct g_geom *,
struct g_consumer *, struct g_provider *);
typedef void g_resize_t(struct g_consumer *cp);
/*
* The g_class structure describes a transformation class. In other words
* all BSD disklabel handlers share one g_class, all MBR handlers share
* one common g_class and so on.
* Certain operations are instantiated on the class, most notably the
* taste and config_geom functions.
*/
struct g_class {
const char *name;
u_int version;
u_int spare0;
g_taste_t *taste;
g_config_t *config;
g_ctl_req_t *ctlreq;
g_init_t *init;
g_fini_t *fini;
g_ctl_destroy_geom_t *destroy_geom;
/*
* Default values for geom methods
*/
g_start_t *start;
g_spoiled_t *spoiled;
g_attrchanged_t *attrchanged;
g_dumpconf_t *dumpconf;
g_access_t *access;
g_orphan_t *orphan;
g_ioctl_t *ioctl;
g_provgone_t *providergone;
g_resize_t *resize;
void *spare1;
void *spare2;
/*
* The remaining elements are private
*/
LIST_ENTRY(g_class) class;
LIST_HEAD(,g_geom) geom;
};
/*
* The g_geom_alias is a list node for aliases for the geom name
* for device node creation.
*/
struct g_geom_alias {
LIST_ENTRY(g_geom_alias) ga_next;
const char *ga_alias;
};
#define G_VERSION_00 0x19950323
#define G_VERSION_01 0x20041207 /* add fflag to g_ioctl_t */
#define G_VERSION G_VERSION_01
/*
* The g_geom is an instance of a g_class.
*/
struct g_geom {
char *name;
struct g_class *class;
LIST_ENTRY(g_geom) geom;
LIST_HEAD(,g_consumer) consumer;
LIST_HEAD(,g_provider) provider;
TAILQ_ENTRY(g_geom) geoms; /* XXX: better name */
int rank;
g_start_t *start;
g_spoiled_t *spoiled;
g_attrchanged_t *attrchanged;
g_dumpconf_t *dumpconf;
g_access_t *access;
g_orphan_t *orphan;
g_ioctl_t *ioctl;
g_provgone_t *providergone;
g_resize_t *resize;
void *spare0;
void *spare1;
void *softc;
unsigned flags;
#define G_GEOM_WITHER 0x01
#define G_GEOM_VOLATILE_BIO 0x02
#define G_GEOM_IN_ACCESS 0x04
#define G_GEOM_ACCESS_WAIT 0x08
LIST_HEAD(,g_geom_alias) aliases;
};
/*
* The g_bioq is a queue of struct bio's.
* XXX: possibly collection point for statistics.
* XXX: should (possibly) be collapsed with sys/bio.h::bio_queue_head.
*/
struct g_bioq {
TAILQ_HEAD(, bio) bio_queue;
struct mtx bio_queue_lock;
int bio_queue_length;
};
/*
* A g_consumer is an attachment point for a g_provider. One g_consumer
* can only be attached to one g_provider, but multiple g_consumers
* can be attached to one g_provider.
*/
struct g_consumer {
struct g_geom *geom;
LIST_ENTRY(g_consumer) consumer;
struct g_provider *provider;
LIST_ENTRY(g_consumer) consumers; /* XXX: better name */
int acr, acw, ace;
int flags;
#define G_CF_SPOILED 0x1
#define G_CF_ORPHAN 0x4
#define G_CF_DIRECT_SEND 0x10
#define G_CF_DIRECT_RECEIVE 0x20
struct devstat *stat;
u_int nstart, nend;
/* Two fields for the implementing class to use */
void *private;
u_int index;
};
/*
* A g_provider is a "logical disk".
*/
struct g_provider {
char *name;
LIST_ENTRY(g_provider) provider;
struct g_geom *geom;
LIST_HEAD(,g_consumer) consumers;
int acr, acw, ace;
int error;
TAILQ_ENTRY(g_provider) orphan;
off_t mediasize;
u_int sectorsize;
u_int stripesize;
u_int stripeoffset;
struct devstat *stat;
u_int nstart, nend;
u_int flags;
#define G_PF_WITHER 0x2
#define G_PF_ORPHAN 0x4
#define G_PF_ACCEPT_UNMAPPED 0x8
#define G_PF_DIRECT_SEND 0x10
#define G_PF_DIRECT_RECEIVE 0x20
/* Two fields for the implementing class to use */
void *private;
u_int index;
};
/*
* Descriptor of a classifier. We can register a function and
* an argument, which is called by g_io_request() on bio's
* that are not previously classified.
*/
struct g_classifier_hook {
TAILQ_ENTRY(g_classifier_hook) link;
int (*func)(void *arg, struct bio *bp);
void *arg;
};
/* BIO_GETATTR("GEOM::setstate") argument values. */
#define G_STATE_FAILED 0
#define G_STATE_REBUILD 1
#define G_STATE_RESYNC 2
#define G_STATE_ACTIVE 3
/* geom_dev.c */
struct cdev;
void g_dev_print(void);
void g_dev_physpath_changed(void);
struct g_provider *g_dev_getprovider(struct cdev *dev);
/* geom_dump.c */
void g_trace(int level, const char *, ...);
# define G_T_TOPOLOGY 1
# define G_T_BIO 2
# define G_T_ACCESS 4
/* geom_event.c */
typedef void g_event_t(void *, int flag);
#define EV_CANCEL 1
int g_post_event(g_event_t *func, void *arg, int flag, ...);
int g_waitfor_event(g_event_t *func, void *arg, int flag, ...);
void g_cancel_event(void *ref);
int g_attr_changed(struct g_provider *pp, const char *attr, int flag);
int g_media_changed(struct g_provider *pp, int flag);
int g_media_gone(struct g_provider *pp, int flag);
void g_orphan_provider(struct g_provider *pp, int error);
void g_waitidlelock(void);
/* geom_subr.c */
int g_access(struct g_consumer *cp, int nread, int nwrite, int nexcl);
int g_attach(struct g_consumer *cp, struct g_provider *pp);
int g_compare_names(const char *namea, const char *nameb);
void g_destroy_consumer(struct g_consumer *cp);
void g_destroy_geom(struct g_geom *pp);
void g_destroy_provider(struct g_provider *pp);
void g_detach(struct g_consumer *cp);
void g_error_provider(struct g_provider *pp, int error);
struct g_provider *g_provider_by_name(char const *arg);
void g_geom_add_alias(struct g_geom *gp, const char *alias);
int g_getattr__(const char *attr, struct g_consumer *cp, void *var, int len);
#define g_getattr(a, c, v) g_getattr__((a), (c), (v), sizeof *(v))
int g_handleattr(struct bio *bp, const char *attribute, const void *val,
int len);
int g_handleattr_int(struct bio *bp, const char *attribute, int val);
int g_handleattr_off_t(struct bio *bp, const char *attribute, off_t val);
int g_handleattr_uint16_t(struct bio *bp, const char *attribute, uint16_t val);
int g_handleattr_str(struct bio *bp, const char *attribute, const char *str);
struct g_consumer * g_new_consumer(struct g_geom *gp);
struct g_geom * g_new_geomf(struct g_class *mp, const char *fmt, ...)
__printflike(2, 3);
struct g_provider * g_new_providerf(struct g_geom *gp, const char *fmt, ...)
__printflike(2, 3);
void g_resize_provider(struct g_provider *pp, off_t size);
int g_retaste(struct g_class *mp);
void g_spoil(struct g_provider *pp, struct g_consumer *cp);
int g_std_access(struct g_provider *pp, int dr, int dw, int de);
void g_std_done(struct bio *bp);
void g_std_spoiled(struct g_consumer *cp);
void g_wither_geom(struct g_geom *gp, int error);
void g_wither_geom_close(struct g_geom *gp, int error);
void g_wither_provider(struct g_provider *pp, int error);
#if defined(DIAGNOSTIC) || defined(DDB)
int g_valid_obj(void const *ptr);
#endif
#ifdef DIAGNOSTIC
#define G_VALID_CLASS(foo) \
KASSERT(g_valid_obj(foo) == 1, ("%p is not a g_class", foo))
#define G_VALID_GEOM(foo) \
KASSERT(g_valid_obj(foo) == 2, ("%p is not a g_geom", foo))
#define G_VALID_CONSUMER(foo) \
KASSERT(g_valid_obj(foo) == 3, ("%p is not a g_consumer", foo))
#define G_VALID_PROVIDER(foo) \
KASSERT(g_valid_obj(foo) == 4, ("%p is not a g_provider", foo))
#else
#define G_VALID_CLASS(foo) do { } while (0)
#define G_VALID_GEOM(foo) do { } while (0)
#define G_VALID_CONSUMER(foo) do { } while (0)
#define G_VALID_PROVIDER(foo) do { } while (0)
#endif
int g_modevent(module_t, int, void *);
/* geom_io.c */
struct bio * g_clone_bio(struct bio *);
struct bio * g_duplicate_bio(struct bio *);
void g_destroy_bio(struct bio *);
void g_io_deliver(struct bio *bp, int error);
int g_io_getattr(const char *attr, struct g_consumer *cp, int *len, void *ptr);
int g_io_zonecmd(struct disk_zone_args *zone_args, struct g_consumer *cp);
int g_io_flush(struct g_consumer *cp);
int g_register_classifier(struct g_classifier_hook *hook);
void g_unregister_classifier(struct g_classifier_hook *hook);
void g_io_request(struct bio *bp, struct g_consumer *cp);
struct bio *g_new_bio(void);
struct bio *g_alloc_bio(void);
void g_reset_bio(struct bio *);
void * g_read_data(struct g_consumer *cp, off_t offset, off_t length, int *error);
int g_write_data(struct g_consumer *cp, off_t offset, void *ptr, off_t length);
int g_delete_data(struct g_consumer *cp, off_t offset, off_t length);
void g_print_bio(struct bio *bp);
int g_use_g_read_data(void *, off_t, void **, int);
int g_use_g_write_data(void *, off_t, void *, int);
/* geom_kern.c / geom_kernsim.c */
#ifdef _KERNEL
extern struct sx topology_lock;
struct g_kerneldump {
off_t offset;
off_t length;
struct dumperinfo di;
};
MALLOC_DECLARE(M_GEOM);
static __inline void *
g_malloc(int size, int flags)
{
void *p;
p = malloc(size, M_GEOM, flags);
return (p);
}
static __inline void
g_free(void *ptr)
{
#ifdef DIAGNOSTIC
if (sx_xlocked(&topology_lock)) {
KASSERT(g_valid_obj(ptr) == 0,
("g_free(%p) of live object, type %d", ptr,
g_valid_obj(ptr)));
}
#endif
free(ptr, M_GEOM);
}
#define g_topology_lock() \
do { \
sx_xlock(&topology_lock); \
} while (0)
#define g_topology_try_lock() sx_try_xlock(&topology_lock)
#define g_topology_unlock() \
do { \
sx_xunlock(&topology_lock); \
} while (0)
#define g_topology_assert() \
do { \
sx_assert(&topology_lock, SX_XLOCKED); \
} while (0)
#define g_topology_assert_not() \
do { \
sx_assert(&topology_lock, SX_UNLOCKED); \
} while (0)
#define g_topology_sleep(chan, timo) \
sx_sleep(chan, &topology_lock, 0, "gtopol", timo)
#define DECLARE_GEOM_CLASS(class, name) \
static moduledata_t name##_mod = { \
#name, g_modevent, &class \
}; \
DECLARE_MODULE(name, name##_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
int g_is_geom_thread(struct thread *td);
#endif /* _KERNEL */
/* geom_ctl.c */
int gctl_set_param(struct gctl_req *req, const char *param, void const *ptr, int len);
void gctl_set_param_err(struct gctl_req *req, const char *param, void const *ptr, int len);
void *gctl_get_param(struct gctl_req *req, const char *param, int *len);
char const *gctl_get_asciiparam(struct gctl_req *req, const char *param);
void *gctl_get_paraml(struct gctl_req *req, const char *param, int len);
int gctl_error(struct gctl_req *req, const char *fmt, ...) __printflike(2, 3);
struct g_class *gctl_get_class(struct gctl_req *req, char const *arg);
struct g_geom *gctl_get_geom(struct gctl_req *req, struct g_class *mpr, char const *arg);
struct g_provider *gctl_get_provider(struct gctl_req *req, char const *arg);
#endif /* _GEOM_GEOM_H_ */
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