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linux/fs/dlm/plock.c
Benjamin Coddington 9d5b86ac13 fs/locks: Remove fl_nspid and use fs-specific l_pid for remote locks 
Since commit c69899a17c "NFSv4: Update of VFS byte range lock must be
atomic with the stateid update", NFSv4 has been inserting locks in rpciod
worker context.  The result is that the file_lock's fl_nspid is the
kworker's pid instead of the original userspace pid.

The fl_nspid is only used to represent the namespaced virtual pid number
when displaying locks or returning from F_GETLK.  There's no reason to set
it for every inserted lock, since we can usually just look it up from
fl_pid.  So, instead of looking up and holding struct pid for every lock,
let's just look up the virtual pid number from fl_pid when it is needed.
That means we can remove fl_nspid entirely.

The translaton and presentation of fl_pid should handle the following four
cases:

1 - F_GETLK on a remote file with a remote lock:
    In this case, the filesystem should determine the l_pid to return here.
    Filesystems should indicate that the fl_pid represents a non-local pid
    value that should not be translated by returning an fl_pid <= 0.

2 - F_GETLK on a local file with a remote lock:
    This should be the l_pid of the lock manager process, and translated.

3 - F_GETLK on a remote file with a local lock, and
4 - F_GETLK on a local file with a local lock:
    These should be the translated l_pid of the local locking process.

Fuse was already doing the correct thing by translating the pid into the
caller's namespace.  With this change we must update fuse to translate
to init's pid namespace, so that the locks API can then translate from
init's pid namespace into the pid namespace of the caller.

With this change, the locks API will expect that if a filesystem returns
a remote pid as opposed to a local pid for F_GETLK, that remote pid will
be <= 0.  This signifies that the pid is remote, and the locks API will
forego translating that pid into the pid namespace of the local calling
process.

Finally, we convert remote filesystems to present remote pids using
negative numbers. Have lustre, 9p, ceph, cifs, and dlm negate the remote
pid returned for F_GETLK lock requests.

Since local pids will never be larger than PID_MAX_LIMIT (which is
currently defined as <= 4 million), but pid_t is an unsigned int, we
should have plenty of room to represent remote pids with negative
numbers if we assume that remote pid numbers are similarly limited.

If this is not the case, then we run the risk of having a remote pid
returned for which there is also a corresponding local pid.  This is a
problem we have now, but this patch should reduce the chances of that
occurring, while also returning those remote pid numbers, for whatever
that may be worth.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
2017-07-16 10:28:22 -04:00

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/*
* Copyright (C) 2005-2008 Red Hat, Inc. All rights reserved.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU General Public License version 2.
*/
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/poll.h>
#include <linux/dlm.h>
#include <linux/dlm_plock.h>
#include <linux/slab.h>
#include "dlm_internal.h"
#include "lockspace.h"
static spinlock_t ops_lock;
static struct list_head send_list;
static struct list_head recv_list;
static wait_queue_head_t send_wq;
static wait_queue_head_t recv_wq;
struct plock_op {
struct list_head list;
int done;
struct dlm_plock_info info;
};
struct plock_xop {
struct plock_op xop;
int (*callback)(struct file_lock *fl, int result);
void *fl;
void *file;
struct file_lock flc;
};
static inline void set_version(struct dlm_plock_info *info)
{
info->version[0] = DLM_PLOCK_VERSION_MAJOR;
info->version[1] = DLM_PLOCK_VERSION_MINOR;
info->version[2] = DLM_PLOCK_VERSION_PATCH;
}
static int check_version(struct dlm_plock_info *info)
{
if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) ||
(DLM_PLOCK_VERSION_MINOR < info->version[1])) {
log_print("plock device version mismatch: "
"kernel (%u.%u.%u), user (%u.%u.%u)",
DLM_PLOCK_VERSION_MAJOR,
DLM_PLOCK_VERSION_MINOR,
DLM_PLOCK_VERSION_PATCH,
info->version[0],
info->version[1],
info->version[2]);
return -EINVAL;
}
return 0;
}
static void send_op(struct plock_op *op)
{
set_version(&op->info);
INIT_LIST_HEAD(&op->list);
spin_lock(&ops_lock);
list_add_tail(&op->list, &send_list);
spin_unlock(&ops_lock);
wake_up(&send_wq);
}
/* If a process was killed while waiting for the only plock on a file,
locks_remove_posix will not see any lock on the file so it won't
send an unlock-close to us to pass on to userspace to clean up the
abandoned waiter. So, we have to insert the unlock-close when the
lock call is interrupted. */
static void do_unlock_close(struct dlm_ls *ls, u64 number,
struct file *file, struct file_lock *fl)
{
struct plock_op *op;
op = kzalloc(sizeof(*op), GFP_NOFS);
if (!op)
return;
op->info.optype = DLM_PLOCK_OP_UNLOCK;
op->info.pid = fl->fl_pid;
op->info.fsid = ls->ls_global_id;
op->info.number = number;
op->info.start = 0;
op->info.end = OFFSET_MAX;
if (fl->fl_lmops && fl->fl_lmops->lm_grant)
op->info.owner = (__u64) fl->fl_pid;
else
op->info.owner = (__u64)(long) fl->fl_owner;
op->info.flags |= DLM_PLOCK_FL_CLOSE;
send_op(op);
}
int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
int cmd, struct file_lock *fl)
{
struct dlm_ls *ls;
struct plock_op *op;
struct plock_xop *xop;
int rv;
ls = dlm_find_lockspace_local(lockspace);
if (!ls)
return -EINVAL;
xop = kzalloc(sizeof(*xop), GFP_NOFS);
if (!xop) {
rv = -ENOMEM;
goto out;
}
op = &xop->xop;
op->info.optype = DLM_PLOCK_OP_LOCK;
op->info.pid = fl->fl_pid;
op->info.ex = (fl->fl_type == F_WRLCK);
op->info.wait = IS_SETLKW(cmd);
op->info.fsid = ls->ls_global_id;
op->info.number = number;
op->info.start = fl->fl_start;
op->info.end = fl->fl_end;
if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
/* fl_owner is lockd which doesn't distinguish
processes on the nfs client */
op->info.owner = (__u64) fl->fl_pid;
xop->callback = fl->fl_lmops->lm_grant;
locks_init_lock(&xop->flc);
locks_copy_lock(&xop->flc, fl);
xop->fl = fl;
xop->file = file;
} else {
op->info.owner = (__u64)(long) fl->fl_owner;
xop->callback = NULL;
}
send_op(op);
if (xop->callback == NULL) {
rv = wait_event_interruptible(recv_wq, (op->done != 0));
if (rv == -ERESTARTSYS) {
log_debug(ls, "dlm_posix_lock: wait killed %llx",
(unsigned long long)number);
spin_lock(&ops_lock);
list_del(&op->list);
spin_unlock(&ops_lock);
kfree(xop);
do_unlock_close(ls, number, file, fl);
goto out;
}
} else {
rv = FILE_LOCK_DEFERRED;
goto out;
}
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_error(ls, "dlm_posix_lock: op on list %llx",
(unsigned long long)number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
rv = op->info.rv;
if (!rv) {
if (locks_lock_file_wait(file, fl) < 0)
log_error(ls, "dlm_posix_lock: vfs lock error %llx",
(unsigned long long)number);
}
kfree(xop);
out:
dlm_put_lockspace(ls);
return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_lock);
/* Returns failure iff a successful lock operation should be canceled */
static int dlm_plock_callback(struct plock_op *op)
{
struct file *file;
struct file_lock *fl;
struct file_lock *flc;
int (*notify)(struct file_lock *fl, int result) = NULL;
struct plock_xop *xop = (struct plock_xop *)op;
int rv = 0;
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_print("dlm_plock_callback: op on list %llx",
(unsigned long long)op->info.number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
/* check if the following 2 are still valid or make a copy */
file = xop->file;
flc = &xop->flc;
fl = xop->fl;
notify = xop->callback;
if (op->info.rv) {
notify(fl, op->info.rv);
goto out;
}
/* got fs lock; bookkeep locally as well: */
flc->fl_flags &= ~FL_SLEEP;
if (posix_lock_file(file, flc, NULL)) {
/*
* This can only happen in the case of kmalloc() failure.
* The filesystem's own lock is the authoritative lock,
* so a failure to get the lock locally is not a disaster.
* As long as the fs cannot reliably cancel locks (especially
* in a low-memory situation), we're better off ignoring
* this failure than trying to recover.
*/
log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
(unsigned long long)op->info.number, file, fl);
}
rv = notify(fl, 0);
if (rv) {
/* XXX: We need to cancel the fs lock here: */
log_print("dlm_plock_callback: lock granted after lock request "
"failed; dangling lock!\n");
goto out;
}
out:
kfree(xop);
return rv;
}
int dlm_posix_unlock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
struct file_lock *fl)
{
struct dlm_ls *ls;
struct plock_op *op;
int rv;
unsigned char fl_flags = fl->fl_flags;
ls = dlm_find_lockspace_local(lockspace);
if (!ls)
return -EINVAL;
op = kzalloc(sizeof(*op), GFP_NOFS);
if (!op) {
rv = -ENOMEM;
goto out;
}
/* cause the vfs unlock to return ENOENT if lock is not found */
fl->fl_flags |= FL_EXISTS;
rv = locks_lock_file_wait(file, fl);
if (rv == -ENOENT) {
rv = 0;
goto out_free;
}
if (rv < 0) {
log_error(ls, "dlm_posix_unlock: vfs unlock error %d %llx",
rv, (unsigned long long)number);
}
op->info.optype = DLM_PLOCK_OP_UNLOCK;
op->info.pid = fl->fl_pid;
op->info.fsid = ls->ls_global_id;
op->info.number = number;
op->info.start = fl->fl_start;
op->info.end = fl->fl_end;
if (fl->fl_lmops && fl->fl_lmops->lm_grant)
op->info.owner = (__u64) fl->fl_pid;
else
op->info.owner = (__u64)(long) fl->fl_owner;
if (fl->fl_flags & FL_CLOSE) {
op->info.flags |= DLM_PLOCK_FL_CLOSE;
send_op(op);
rv = 0;
goto out;
}
send_op(op);
wait_event(recv_wq, (op->done != 0));
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_error(ls, "dlm_posix_unlock: op on list %llx",
(unsigned long long)number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
rv = op->info.rv;
if (rv == -ENOENT)
rv = 0;
out_free:
kfree(op);
out:
dlm_put_lockspace(ls);
fl->fl_flags = fl_flags;
return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_unlock);
int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
struct file_lock *fl)
{
struct dlm_ls *ls;
struct plock_op *op;
int rv;
ls = dlm_find_lockspace_local(lockspace);
if (!ls)
return -EINVAL;
op = kzalloc(sizeof(*op), GFP_NOFS);
if (!op) {
rv = -ENOMEM;
goto out;
}
op->info.optype = DLM_PLOCK_OP_GET;
op->info.pid = fl->fl_pid;
op->info.ex = (fl->fl_type == F_WRLCK);
op->info.fsid = ls->ls_global_id;
op->info.number = number;
op->info.start = fl->fl_start;
op->info.end = fl->fl_end;
if (fl->fl_lmops && fl->fl_lmops->lm_grant)
op->info.owner = (__u64) fl->fl_pid;
else
op->info.owner = (__u64)(long) fl->fl_owner;
send_op(op);
wait_event(recv_wq, (op->done != 0));
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_error(ls, "dlm_posix_get: op on list %llx",
(unsigned long long)number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
/* info.rv from userspace is 1 for conflict, 0 for no-conflict,
-ENOENT if there are no locks on the file */
rv = op->info.rv;
fl->fl_type = F_UNLCK;
if (rv == -ENOENT)
rv = 0;
else if (rv > 0) {
locks_init_lock(fl);
fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
fl->fl_flags = FL_POSIX;
fl->fl_pid = -op->info.pid;
fl->fl_start = op->info.start;
fl->fl_end = op->info.end;
rv = 0;
}
kfree(op);
out:
dlm_put_lockspace(ls);
return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_get);
/* a read copies out one plock request from the send list */
static ssize_t dev_read(struct file *file, char __user *u, size_t count,
loff_t *ppos)
{
struct dlm_plock_info info;
struct plock_op *op = NULL;
if (count < sizeof(info))
return -EINVAL;
spin_lock(&ops_lock);
if (!list_empty(&send_list)) {
op = list_entry(send_list.next, struct plock_op, list);
if (op->info.flags & DLM_PLOCK_FL_CLOSE)
list_del(&op->list);
else
list_move(&op->list, &recv_list);
memcpy(&info, &op->info, sizeof(info));
}
spin_unlock(&ops_lock);
if (!op)
return -EAGAIN;
/* there is no need to get a reply from userspace for unlocks
that were generated by the vfs cleaning up for a close
(the process did not make an unlock call). */
if (op->info.flags & DLM_PLOCK_FL_CLOSE)
kfree(op);
if (copy_to_user(u, &info, sizeof(info)))
return -EFAULT;
return sizeof(info);
}
/* a write copies in one plock result that should match a plock_op
on the recv list */
static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
loff_t *ppos)
{
struct dlm_plock_info info;
struct plock_op *op;
int found = 0, do_callback = 0;
if (count != sizeof(info))
return -EINVAL;
if (copy_from_user(&info, u, sizeof(info)))
return -EFAULT;
if (check_version(&info))
return -EINVAL;
spin_lock(&ops_lock);
list_for_each_entry(op, &recv_list, list) {
if (op->info.fsid == info.fsid &&
op->info.number == info.number &&
op->info.owner == info.owner) {
struct plock_xop *xop = (struct plock_xop *)op;
list_del_init(&op->list);
memcpy(&op->info, &info, sizeof(info));
if (xop->callback)
do_callback = 1;
else
op->done = 1;
found = 1;
break;
}
}
spin_unlock(&ops_lock);
if (found) {
if (do_callback)
dlm_plock_callback(op);
else
wake_up(&recv_wq);
} else
log_print("dev_write no op %x %llx", info.fsid,
(unsigned long long)info.number);
return count;
}
static unsigned int dev_poll(struct file *file, poll_table *wait)
{
unsigned int mask = 0;
poll_wait(file, &send_wq, wait);
spin_lock(&ops_lock);
if (!list_empty(&send_list))
mask = POLLIN | POLLRDNORM;
spin_unlock(&ops_lock);
return mask;
}
static const struct file_operations dev_fops = {
.read = dev_read,
.write = dev_write,
.poll = dev_poll,
.owner = THIS_MODULE,
.llseek = noop_llseek,
};
static struct miscdevice plock_dev_misc = {
.minor = MISC_DYNAMIC_MINOR,
.name = DLM_PLOCK_MISC_NAME,
.fops = &dev_fops
};
int dlm_plock_init(void)
{
int rv;
spin_lock_init(&ops_lock);
INIT_LIST_HEAD(&send_list);
INIT_LIST_HEAD(&recv_list);
init_waitqueue_head(&send_wq);
init_waitqueue_head(&recv_wq);
rv = misc_register(&plock_dev_misc);
if (rv)
log_print("dlm_plock_init: misc_register failed %d", rv);
return rv;
}
void dlm_plock_exit(void)
{
misc_deregister(&plock_dev_misc);
}
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