d/freebsd-nq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Don't try so hard to make the lower 16 bits of fsids unique. It tended

Browse Source 
to recycle full fsids after only 16 mount/unmount's.  This is probably
too often for exported fsids.  Now we recycle the full fsids only
after 2^16 mount/ umount's and only ensure uniqueness in the lower 16
bits if there have been <= 256 calls to vfs_getnewfsid() since the
system started.
This commit is contained in:
Bruce Evans 2000-03-14 14:19:49 +00:00
parent 44dfd6a858
commit 05ecdd7037
2 changed files with 26 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
sys/kern/vfs_export.c
View File

@ -328,40 +328,31 @@ vfs_getvfs(fsid)
}
/*
* Get a new unique fsid. Try to make its val[0] unique mod 2^16, since
* this value may be used to create fake device numbers for stat(), and
* some emulators only support 16-bit device numbers.
* Get a new unique fsid. Try to make its val[0] unique, since this value
* will be used to create fake device numbers for stat(). Also try (but
* not so hard) make its val[0] unique mod 2^16, since some emulators only
* support 16-bit device numbers. We end up with unique val[0]'s for the
* first 2^16 calls and unique val[0]'s mod 2^16 for the first 2^8 calls.
*
* Keep in mind that several mounts may be running in parallel. Starting
* the search one past where the previous search terminated (mod 0x10) is
* both a micro-optimization and (incomplete) defense against returning
* the same fsid to different mounts.
* the search one past where the previous search terminated is both a
* micro-optimization and a defense against returning the same fsid to
* different mounts.
*/
void
vfs_getnewfsid(mp)
struct mount *mp;
{
static u_int mntid_base;
static u_int16_t mntid_base;
fsid_t tfsid;
u_int i;
int mtype, mynor;
int mtype;
simple_lock(&mntid_slock);
mtype = mp->mnt_vfc->vfc_typenum;
tfsid.val[1] = mtype;
for (i = 0; ; i++) {
/*
* mtype needs to be uniquely encoded in the minor number
* so that uniqueness of the full fsid implies uniqueness
* of the device number. We are short of bits and only
* guarantee uniqueness of the device number mod 2^16 if
* mtype is always < 16 and there are never more than
* 16 mounts per vfs type.
*/
mynor = ((mntid_base++ & 0xFFFFF) << 4) | (mtype & 0xF);
if (i < 0x10)
mynor &= 0xFF;
tfsid.val[0] = makeudev(255, mynor);
mtype = (mtype & 0xFF) << 16;
for (;;) {
tfsid.val[0] = makeudev(255, mtype | mntid_base++);
if (vfs_getvfs(&tfsid) == NULL)
break;
}

35
sys/kern/vfs_subr.c
View File

@ -328,40 +328,31 @@ vfs_getvfs(fsid)
}
/*
* Get a new unique fsid. Try to make its val[0] unique mod 2^16, since
* this value may be used to create fake device numbers for stat(), and
* some emulators only support 16-bit device numbers.
* Get a new unique fsid. Try to make its val[0] unique, since this value
* will be used to create fake device numbers for stat(). Also try (but
* not so hard) make its val[0] unique mod 2^16, since some emulators only
* support 16-bit device numbers. We end up with unique val[0]'s for the
* first 2^16 calls and unique val[0]'s mod 2^16 for the first 2^8 calls.
*
* Keep in mind that several mounts may be running in parallel. Starting
* the search one past where the previous search terminated (mod 0x10) is
* both a micro-optimization and (incomplete) defense against returning
* the same fsid to different mounts.
* the search one past where the previous search terminated is both a
* micro-optimization and a defense against returning the same fsid to
* different mounts.
*/
void
vfs_getnewfsid(mp)
struct mount *mp;
{
static u_int mntid_base;
static u_int16_t mntid_base;
fsid_t tfsid;
u_int i;
int mtype, mynor;
int mtype;
simple_lock(&mntid_slock);
mtype = mp->mnt_vfc->vfc_typenum;
tfsid.val[1] = mtype;
for (i = 0; ; i++) {
/*
* mtype needs to be uniquely encoded in the minor number
* so that uniqueness of the full fsid implies uniqueness
* of the device number. We are short of bits and only
* guarantee uniqueness of the device number mod 2^16 if
* mtype is always < 16 and there are never more than
* 16 mounts per vfs type.
*/
mynor = ((mntid_base++ & 0xFFFFF) << 4) | (mtype & 0xF);
if (i < 0x10)
mynor &= 0xFF;
tfsid.val[0] = makeudev(255, mynor);
mtype = (mtype & 0xFF) << 16;
for (;;) {
tfsid.val[0] = makeudev(255, mtype | mntid_base++);
if (vfs_getvfs(&tfsid) == NULL)
break;
}