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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-25 21:54:06 +08:00
linux-next/fs/afs/rotate.c
David Howells 0fafdc9f88 afs: Fix file locking
Fix the AFS file locking whereby the use of the big kernel lock (which
could be slept with) was replaced by a spinlock (which couldn't).  The
problem is that the AFS code was doing stuff inside the critical section
that might call schedule(), so this is a broken transformation.

Fix this by the following means:

 (1) Use a state machine with a proper state that can only be changed under
     the spinlock rather than using a collection of bit flags.

 (2) Cache the key used for the lock and the lock type in the afs_vnode
     struct so that the manager work function doesn't have to refer to a
     file_lock struct that's been dequeued.  This makes signal handling
     safer.

 (4) Move the unlock from afs_do_unlk() to afs_fl_release_private() which
     means that unlock is achieved in other circumstances too.

 (5) Unlock the file on the server before taking the next conflicting lock.

Also change:

 (1) Check the permits on a file before actually trying the lock.

 (2) fsync the file before effecting an explicit unlock operation.  We
     don't fsync if the lock is erased otherwise as we might not be in a
     context where we can actually do that.

Further fixes:

 (1) Fixed-fileserver address rotation is made to work.  It's only used by
     the locking functions, so couldn't be tested before.

Fixes: 72f98e7255 ("locks: turn lock_flocks into a spinlock")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: jlayton@redhat.com
2017-11-17 10:06:13 +00:00

758 lines
19 KiB
C

/* Handle fileserver selection and rotation.
*
* Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/sched/signal.h>
#include "internal.h"
#include "afs_fs.h"
/*
* Initialise a filesystem server cursor for iterating over FS servers.
*/
void afs_init_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
{
memset(fc, 0, sizeof(*fc));
}
/*
* Begin an operation on the fileserver.
*
* Fileserver operations are serialised on the server by vnode, so we serialise
* them here also using the io_lock.
*/
bool afs_begin_vnode_operation(struct afs_fs_cursor *fc, struct afs_vnode *vnode,
struct key *key)
{
afs_init_fs_cursor(fc, vnode);
fc->vnode = vnode;
fc->key = key;
fc->ac.error = SHRT_MAX;
if (mutex_lock_interruptible(&vnode->io_lock) < 0) {
fc->ac.error = -EINTR;
fc->flags |= AFS_FS_CURSOR_STOP;
return false;
}
if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
fc->flags |= AFS_FS_CURSOR_CUR_ONLY;
return true;
}
/*
* Begin iteration through a server list, starting with the vnode's last used
* server if possible, or the last recorded good server if not.
*/
static bool afs_start_fs_iteration(struct afs_fs_cursor *fc,
struct afs_vnode *vnode)
{
struct afs_cb_interest *cbi;
int i;
read_lock(&vnode->volume->servers_lock);
fc->server_list = afs_get_serverlist(vnode->volume->servers);
read_unlock(&vnode->volume->servers_lock);
cbi = vnode->cb_interest;
if (cbi) {
/* See if the vnode's preferred record is still available */
for (i = 0; i < fc->server_list->nr_servers; i++) {
if (fc->server_list->servers[i].cb_interest == cbi) {
fc->start = i;
goto found_interest;
}
}
/* If we have a lock outstanding on a server that's no longer
* serving this vnode, then we can't switch to another server
* and have to return an error.
*/
if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
fc->ac.error = -ESTALE;
return false;
}
/* Note that the callback promise is effectively broken */
write_seqlock(&vnode->cb_lock);
ASSERTCMP(cbi, ==, vnode->cb_interest);
vnode->cb_interest = NULL;
if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
vnode->cb_break++;
write_sequnlock(&vnode->cb_lock);
afs_put_cb_interest(afs_v2net(vnode), cbi);
cbi = NULL;
} else {
fc->start = READ_ONCE(fc->server_list->index);
}
found_interest:
fc->index = fc->start;
return true;
}
/*
* Post volume busy note.
*/
static void afs_busy(struct afs_volume *volume, u32 abort_code)
{
const char *m;
switch (abort_code) {
case VOFFLINE: m = "offline"; break;
case VRESTARTING: m = "restarting"; break;
case VSALVAGING: m = "being salvaged"; break;
default: m = "busy"; break;
}
pr_notice("kAFS: Volume %u '%s' is %s\n", volume->vid, volume->name, m);
}
/*
* Sleep and retry the operation to the same fileserver.
*/
static bool afs_sleep_and_retry(struct afs_fs_cursor *fc)
{
msleep_interruptible(1000);
if (signal_pending(current)) {
fc->ac.error = -ERESTARTSYS;
return false;
}
return true;
}
/*
* Select the fileserver to use. May be called multiple times to rotate
* through the fileservers.
*/
bool afs_select_fileserver(struct afs_fs_cursor *fc)
{
struct afs_addr_list *alist;
struct afs_server *server;
struct afs_vnode *vnode = fc->vnode;
_enter("%u/%u,%u/%u,%d,%d",
fc->index, fc->start,
fc->ac.index, fc->ac.start,
fc->ac.error, fc->ac.abort_code);
if (fc->flags & AFS_FS_CURSOR_STOP) {
_leave(" = f [stopped]");
return false;
}
/* Evaluate the result of the previous operation, if there was one. */
switch (fc->ac.error) {
case SHRT_MAX:
goto start;
case 0:
default:
/* Success or local failure. Stop. */
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [okay/local %d]", fc->ac.error);
return false;
case -ECONNABORTED:
/* The far side rejected the operation on some grounds. This
* might involve the server being busy or the volume having been moved.
*/
switch (fc->ac.abort_code) {
case VNOVOL:
/* This fileserver doesn't know about the volume.
* - May indicate that the VL is wrong - retry once and compare
* the results.
* - May indicate that the fileserver couldn't attach to the vol.
*/
if (fc->flags & AFS_FS_CURSOR_VNOVOL) {
fc->ac.error = -EREMOTEIO;
goto failed;
}
write_lock(&vnode->volume->servers_lock);
fc->server_list->vnovol_mask |= 1 << fc->index;
write_unlock(&vnode->volume->servers_lock);
set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
if (fc->ac.error < 0)
goto failed;
if (test_bit(AFS_VOLUME_DELETED, &vnode->volume->flags)) {
fc->ac.error = -ENOMEDIUM;
goto failed;
}
/* If the server list didn't change, then assume that
* it's the fileserver having trouble.
*/
if (vnode->volume->servers == fc->server_list) {
fc->ac.error = -EREMOTEIO;
goto failed;
}
/* Try again */
fc->flags |= AFS_FS_CURSOR_VNOVOL;
_leave(" = t [vnovol]");
return true;
case VSALVAGE: /* TODO: Should this return an error or iterate? */
case VVOLEXISTS:
case VNOSERVICE:
case VONLINE:
case VDISKFULL:
case VOVERQUOTA:
fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
goto next_server;
case VOFFLINE:
if (!test_and_set_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags)) {
afs_busy(vnode->volume, fc->ac.abort_code);
clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
}
if (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
fc->ac.error = -EADV;
goto failed;
}
if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
fc->ac.error = -ESTALE;
goto failed;
}
goto busy;
case VSALVAGING:
case VRESTARTING:
case VBUSY:
/* Retry after going round all the servers unless we
* have a file lock we need to maintain.
*/
if (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
fc->ac.error = -EBUSY;
goto failed;
}
if (!test_and_set_bit(AFS_VOLUME_BUSY, &vnode->volume->flags)) {
afs_busy(vnode->volume, fc->ac.abort_code);
clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
}
busy:
if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
if (!afs_sleep_and_retry(fc))
goto failed;
/* Retry with same server & address */
_leave(" = t [vbusy]");
return true;
}
fc->flags |= AFS_FS_CURSOR_VBUSY;
goto next_server;
case VMOVED:
/* The volume migrated to another server. We consider
* consider all locks and callbacks broken and request
* an update from the VLDB.
*
* We also limit the number of VMOVED hops we will
* honour, just in case someone sets up a loop.
*/
if (fc->flags & AFS_FS_CURSOR_VMOVED) {
fc->ac.error = -EREMOTEIO;
goto failed;
}
fc->flags |= AFS_FS_CURSOR_VMOVED;
set_bit(AFS_VOLUME_WAIT, &vnode->volume->flags);
set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
if (fc->ac.error < 0)
goto failed;
/* If the server list didn't change, then the VLDB is
* out of sync with the fileservers. This is hopefully
* a temporary condition, however, so we don't want to
* permanently block access to the file.
*
* TODO: Try other fileservers if we can.
*
* TODO: Retry a few times with sleeps.
*/
if (vnode->volume->servers == fc->server_list) {
fc->ac.error = -ENOMEDIUM;
goto failed;
}
goto restart_from_beginning;
default:
clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
goto failed;
}
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
case -ETIMEDOUT:
case -ETIME:
_debug("no conn");
goto iterate_address;
}
restart_from_beginning:
_debug("restart");
afs_end_cursor(&fc->ac);
afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
fc->cbi = NULL;
afs_put_serverlist(afs_v2net(vnode), fc->server_list);
fc->server_list = NULL;
start:
_debug("start");
/* See if we need to do an update of the volume record. Note that the
* volume may have moved or even have been deleted.
*/
fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
if (fc->ac.error < 0)
goto failed;
if (!afs_start_fs_iteration(fc, vnode))
goto failed;
goto use_server;
next_server:
_debug("next");
afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
fc->cbi = NULL;
fc->index++;
if (fc->index >= fc->server_list->nr_servers)
fc->index = 0;
if (fc->index != fc->start)
goto use_server;
/* That's all the servers poked to no good effect. Try again if some
* of them were busy.
*/
if (fc->flags & AFS_FS_CURSOR_VBUSY)
goto restart_from_beginning;
fc->ac.error = -EDESTADDRREQ;
goto failed;
use_server:
_debug("use");
/* We're starting on a different fileserver from the list. We need to
* check it, create a callback intercept, find its address list and
* probe its capabilities before we use it.
*/
ASSERTCMP(fc->ac.alist, ==, NULL);
server = fc->server_list->servers[fc->index].server;
if (!afs_check_server_record(fc, server))
goto failed;
_debug("USING SERVER: %pU", &server->uuid);
/* Make sure we've got a callback interest record for this server. We
* have to link it in before we send the request as we can be sent a
* break request before we've finished decoding the reply and
* installing the vnode.
*/
fc->ac.error = afs_register_server_cb_interest(
vnode, &fc->server_list->servers[fc->index]);
if (fc->ac.error < 0)
goto failed;
fc->cbi = afs_get_cb_interest(vnode->cb_interest);
read_lock(&server->fs_lock);
alist = rcu_dereference_protected(server->addresses,
lockdep_is_held(&server->fs_lock));
afs_get_addrlist(alist);
read_unlock(&server->fs_lock);
/* Probe the current fileserver if we haven't done so yet. */
if (!test_bit(AFS_SERVER_FL_PROBED, &server->flags)) {
fc->ac.alist = afs_get_addrlist(alist);
if (!afs_probe_fileserver(fc))
goto failed;
}
if (!fc->ac.alist)
fc->ac.alist = alist;
else
afs_put_addrlist(alist);
fc->ac.addr = NULL;
fc->ac.start = READ_ONCE(alist->index);
fc->ac.index = fc->ac.start;
fc->ac.error = 0;
fc->ac.begun = false;
goto iterate_address;
iterate_address:
ASSERT(fc->ac.alist);
_debug("iterate %d/%d", fc->ac.index, fc->ac.alist->nr_addrs);
/* Iterate over the current server's address list to try and find an
* address on which it will respond to us.
*/
if (afs_iterate_addresses(&fc->ac)) {
_leave(" = t");
return true;
}
afs_end_cursor(&fc->ac);
goto next_server;
failed:
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [failed %d]", fc->ac.error);
return false;
}
/*
* Select the same fileserver we used for a vnode before and only that
* fileserver. We use this when we have a lock on that file, which is backed
* only by the fileserver we obtained it from.
*/
bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
{
struct afs_vnode *vnode = fc->vnode;
struct afs_cb_interest *cbi = vnode->cb_interest;
struct afs_addr_list *alist;
_enter("");
switch (fc->ac.error) {
case SHRT_MAX:
if (!cbi) {
fc->ac.error = -ESTALE;
fc->flags |= AFS_FS_CURSOR_STOP;
return false;
}
fc->cbi = afs_get_cb_interest(vnode->cb_interest);
read_lock(&cbi->server->fs_lock);
alist = rcu_dereference_protected(cbi->server->addresses,
lockdep_is_held(&cbi->server->fs_lock));
afs_get_addrlist(alist);
read_unlock(&cbi->server->fs_lock);
if (!alist) {
fc->ac.error = -ESTALE;
fc->flags |= AFS_FS_CURSOR_STOP;
return false;
}
fc->ac.alist = alist;
fc->ac.addr = NULL;
fc->ac.start = READ_ONCE(alist->index);
fc->ac.index = fc->ac.start;
fc->ac.error = 0;
fc->ac.begun = false;
goto iterate_address;
case 0:
default:
/* Success or local failure. Stop. */
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [okay/local %d]", fc->ac.error);
return false;
case -ECONNABORTED:
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [abort]");
return false;
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
case -ETIMEDOUT:
case -ETIME:
_debug("no conn");
goto iterate_address;
}
iterate_address:
/* Iterate over the current server's address list to try and find an
* address on which it will respond to us.
*/
if (afs_iterate_addresses(&fc->ac)) {
_leave(" = t");
return true;
}
afs_end_cursor(&fc->ac);
return false;
}
/*
* Tidy up a filesystem cursor and unlock the vnode.
*/
int afs_end_vnode_operation(struct afs_fs_cursor *fc)
{
struct afs_net *net = afs_v2net(fc->vnode);
int ret;
mutex_unlock(&fc->vnode->io_lock);
afs_end_cursor(&fc->ac);
afs_put_cb_interest(net, fc->cbi);
afs_put_serverlist(net, fc->server_list);
ret = fc->ac.error;
if (ret == -ECONNABORTED)
afs_abort_to_error(fc->ac.abort_code);
return fc->ac.error;
}
#if 0
/*
* Set a filesystem server cursor for using a specific FS server.
*/
int afs_set_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
{
afs_init_fs_cursor(fc, vnode);
read_seqlock_excl(&vnode->cb_lock);
if (vnode->cb_interest) {
if (vnode->cb_interest->server->fs_state == 0)
fc->server = afs_get_server(vnode->cb_interest->server);
else
fc->ac.error = vnode->cb_interest->server->fs_state;
} else {
fc->ac.error = -ESTALE;
}
read_sequnlock_excl(&vnode->cb_lock);
return fc->ac.error;
}
/*
* pick a server to use to try accessing this volume
* - returns with an elevated usage count on the server chosen
*/
bool afs_volume_pick_fileserver(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
{
struct afs_volume *volume = vnode->volume;
struct afs_server *server;
int ret, state, loop;
_enter("%s", volume->vlocation->vldb.name);
/* stick with the server we're already using if we can */
if (vnode->cb_interest && vnode->cb_interest->server->fs_state == 0) {
fc->server = afs_get_server(vnode->cb_interest->server);
goto set_server;
}
down_read(&volume->server_sem);
/* handle the no-server case */
if (volume->nservers == 0) {
fc->ac.error = volume->rjservers ? -ENOMEDIUM : -ESTALE;
up_read(&volume->server_sem);
_leave(" = f [no servers %d]", fc->ac.error);
return false;
}
/* basically, just search the list for the first live server and use
* that */
ret = 0;
for (loop = 0; loop < volume->nservers; loop++) {
server = volume->servers[loop];
state = server->fs_state;
_debug("consider %d [%d]", loop, state);
switch (state) {
case 0:
goto picked_server;
case -ENETUNREACH:
if (ret == 0)
ret = state;
break;
case -EHOSTUNREACH:
if (ret == 0 ||
ret == -ENETUNREACH)
ret = state;
break;
case -ECONNREFUSED:
if (ret == 0 ||
ret == -ENETUNREACH ||
ret == -EHOSTUNREACH)
ret = state;
break;
default:
case -EREMOTEIO:
if (ret == 0 ||
ret == -ENETUNREACH ||
ret == -EHOSTUNREACH ||
ret == -ECONNREFUSED)
ret = state;
break;
}
}
error:
fc->ac.error = ret;
/* no available servers
* - TODO: handle the no active servers case better
*/
up_read(&volume->server_sem);
_leave(" = f [%d]", fc->ac.error);
return false;
picked_server:
/* Found an apparently healthy server. We need to register an interest
* in receiving callbacks before we talk to it.
*/
ret = afs_register_server_cb_interest(vnode,
&volume->cb_interests[loop], server);
if (ret < 0)
goto error;
fc->server = afs_get_server(server);
up_read(&volume->server_sem);
set_server:
fc->ac.alist = afs_get_addrlist(fc->server->addrs);
fc->ac.addr = &fc->ac.alist->addrs[0];
_debug("USING SERVER: %pIS\n", &fc->ac.addr->transport);
_leave(" = t (picked %pIS)", &fc->ac.addr->transport);
return true;
}
/*
* release a server after use
* - releases the ref on the server struct that was acquired by picking
* - records result of using a particular server to access a volume
* - return true to try again, false if okay or to issue error
* - the caller must release the server struct if result was false
*/
bool afs_iterate_fs_cursor(struct afs_fs_cursor *fc,
struct afs_vnode *vnode)
{
struct afs_volume *volume = vnode->volume;
struct afs_server *server = fc->server;
unsigned loop;
_enter("%s,%pIS,%d",
volume->vlocation->vldb.name, &fc->ac.addr->transport,
fc->ac.error);
switch (fc->ac.error) {
/* success */
case 0:
server->fs_state = 0;
_leave(" = f");
return false;
/* the fileserver denied all knowledge of the volume */
case -ENOMEDIUM:
down_write(&volume->server_sem);
/* firstly, find where the server is in the active list (if it
* is) */
for (loop = 0; loop < volume->nservers; loop++)
if (volume->servers[loop] == server)
goto present;
/* no longer there - may have been discarded by another op */
goto try_next_server_upw;
present:
volume->nservers--;
memmove(&volume->servers[loop],
&volume->servers[loop + 1],
sizeof(volume->servers[loop]) *
(volume->nservers - loop));
volume->servers[volume->nservers] = NULL;
afs_put_server(afs_v2net(vnode), server);
volume->rjservers++;
if (volume->nservers > 0)
/* another server might acknowledge its existence */
goto try_next_server_upw;
/* handle the case where all the fileservers have rejected the
* volume
* - TODO: try asking the fileservers for volume information
* - TODO: contact the VL server again to see if the volume is
* no longer registered
*/
up_write(&volume->server_sem);
afs_put_server(afs_v2net(vnode), server);
fc->server = NULL;
_leave(" = f [completely rejected]");
return false;
/* problem reaching the server */
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
case -ETIME:
case -ETIMEDOUT:
case -EREMOTEIO:
/* mark the server as dead
* TODO: vary dead timeout depending on error
*/
spin_lock(&server->fs_lock);
if (!server->fs_state) {
server->fs_state = fc->ac.error;
printk("kAFS: SERVER DEAD state=%d\n", fc->ac.error);
}
spin_unlock(&server->fs_lock);
goto try_next_server;
/* miscellaneous error */
default:
case -ENOMEM:
case -ENONET:
/* tell the caller to accept the result */
afs_put_server(afs_v2net(vnode), server);
fc->server = NULL;
_leave(" = f [local failure]");
return false;
}
/* tell the caller to loop around and try the next server */
try_next_server_upw:
up_write(&volume->server_sem);
try_next_server:
afs_put_server(afs_v2net(vnode), server);
_leave(" = t [try next server]");
return true;
}
/*
* Clean up a fileserver cursor.
*/
int afs_end_fs_cursor(struct afs_fs_cursor *fc, struct afs_net *net)
{
afs_end_cursor(&fc->ac);
afs_put_server(net, fc->server);
return fc->ac.error;
}
#endif