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Expose API to allow disks to ask for alias names in devfs.

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Implement disk_add_alias to allow aliases to be added to disks. All
disk have a primary name (say "foo") can also have secondary names
(say "bar") such that all instances of "foo" also have a "bar"
alias. So if you have foo0, foo0p1, foo1, foo1s1 and foo1s1a nodes
created by the foo driver and gpart, device nodes bar0, bar0p1, bar1,
bar1s1 and bar1s1a will appear as symlinks back to the original nodes.
This generalizes to multiple aliases. However, since the unit number
follows the primary name, multiple device drivers can't create the
same aliases unless those drives coorinate the unit number space (eg
you couldn't add an alias 'disk' to both 'da' and 'ada' because it's
possible to have da0 and ada0, because 'disk0' is ambiguous).

Differential Revision: https://reviews.freebsd.org/D11873
This commit is contained in:
Warner Losh 2017-08-07 21:12:38 +00:00
parent 5d7d13290a
commit d3517d306c
3 changed files with 57 additions and 3 deletions
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26
share/man/man9/disk.9
View File

@ -27,7 +27,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd October 30, 2012
.Dd August 3, 2017
.Dt DISK 9
.Os
.Sh NAME
@ -45,6 +45,8 @@
.Fn disk_destroy "struct disk *disk"
.Ft int
.Fn disk_resize "struct disk *disk" "int flags"
.Ft void
.Fn disk_add_alias "struct disk *disk" "const char *alias"
.Sh DESCRIPTION
The disk storage API permits kernel device drivers providing access to
disk-like storage devices to advertise the device to other kernel
@ -69,6 +71,20 @@ function,
fill in the fields and call
.Fn disk_create
when the device is ready to service requests.
.Fn disk_add_alias
adds an alias for the disk and must be called before
.Fn disk_create ,
but may be called multiple times.
For each alias added, a device node will be created with
.Xr make_dev_alias 9
in the same way primary device nodes are created with
.Xr make_dev 9
for
.Va d_name
and
.Va d_unit .
Care should be taken to ensure that only one driver creates aliases
for any given name.
.Fn disk_resize
can be called by the driver after modifying
.Va d_mediasize
@ -227,7 +243,13 @@ structure for this disk device.
.El
.Sh SEE ALSO
.Xr GEOM 4 ,
.Xr devfs 5
.Xr devfs 5 ,
.Xr MAKE_DEV 9
.Sh AUTHORS
This manual page was written by
.An Robert Watson .
.Sh BUGS
Disk aliases are not a general purpose aliasing mechanism, but are
intended only to ease the transition from one name to another.
They can be used to ensure that nvd0 and nda0 are the same thing.
They cannot be used to implement the diskX concept from macOS.

25
sys/geom/geom_disk.c
View File

@ -676,6 +676,7 @@ g_disk_create(void *arg, int flag)
struct g_provider *pp;
struct disk *dp;
struct g_disk_softc *sc;
struct disk_alias *dap;
char tmpstr[80];
if (flag == EV_CANCEL)
@ -704,6 +705,10 @@ g_disk_create(void *arg, int flag)
sc->dp = dp;
gp = g_new_geomf(&g_disk_class, "%s%d", dp->d_name, dp->d_unit);
gp->softc = sc;
LIST_FOREACH(dap, &dp->d_aliases, da_next) {
snprintf(tmpstr, sizeof(tmpstr), "%s%d", dap->da_alias, dp->d_unit);
g_geom_add_alias(gp, tmpstr);
}
pp = g_new_providerf(gp, "%s", gp->name);
devstat_remove_entry(pp->stat);
pp->stat = NULL;
@ -791,6 +796,7 @@ g_disk_destroy(void *ptr, int flag)
struct disk *dp;
struct g_geom *gp;
struct g_disk_softc *sc;
struct disk_alias *dap, *daptmp;
g_topology_assert();
dp = ptr;
@ -802,6 +808,8 @@ g_disk_destroy(void *ptr, int flag)
dp->d_geom = NULL;
g_wither_geom(gp, ENXIO);
}
LIST_FOREACH_SAFE(dap, &dp->d_aliases, da_next, daptmp)
g_free(dap);
g_free(dp);
}
@ -834,8 +842,11 @@ g_disk_ident_adjust(char *ident, size_t size)
struct disk *
disk_alloc(void)
{
struct disk *dp;
return (g_malloc(sizeof(struct disk), M_WAITOK | M_ZERO));
dp = g_malloc(sizeof(struct disk), M_WAITOK | M_ZERO);
LIST_INIT(&dp->d_aliases);
return (dp);
}
void
@ -884,6 +895,18 @@ disk_destroy(struct disk *dp)
g_post_event(g_disk_destroy, dp, M_WAITOK, NULL);
}
void
disk_add_alias(struct disk *dp, const char *name)
{
struct disk_alias *dap;
dap = (struct disk_alias *)g_malloc(
sizeof(struct disk_alias) + strlen(name) + 1, M_WAITOK);
strcpy((char *)(dap + 1), name);
dap->da_alias = (const char *)(dap + 1);
LIST_INSERT_HEAD(&dp->d_aliases, dap, da_next);
}
void
disk_gone(struct disk *dp)
{

9
sys/geom/geom_disk.h
View File

@ -66,6 +66,11 @@ typedef enum {
DISK_INIT_DONE
} disk_init_level;
struct disk_alias {
LIST_ENTRY(disk_alias) da_next;
const char *da_alias;
};
struct disk {
/* Fields which are private to geom_disk */
struct g_geom *d_geom;
@ -109,6 +114,9 @@ struct disk {
/* Fields private to the driver */
void *d_drv1;
/* Fields private to geom_disk, to be moved on next version bump */
LIST_HEAD(,disk_alias) d_aliases;
};
#define DISKFLAG_RESERVED 0x1 /* Was NEEDSGIANT */
@ -132,6 +140,7 @@ void disk_attr_changed(struct disk *dp, const char *attr, int flag);
void disk_media_changed(struct disk *dp, int flag);
void disk_media_gone(struct disk *dp, int flag);
int disk_resize(struct disk *dp, int flag);
void disk_add_alias(struct disk *disk, const char *);
#define DISK_VERSION_00 0x58561059
#define DISK_VERSION_01 0x5856105a