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nfsd: remove fault injection code 

It was an interesting idea but nobody seems to be using it, it's buggy
at this point, and nfs4state.c is already complicated enough without it.
The new nfsd/clients/ code provides some of the same functionality, and
could probably do more if desired.

This feature has been deprecated since 9d60d93198 ("Deprecate nfsd
fault injection").

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
J. Bruce Fields 2020-07-30 20:33:57 -04:00
parent 856deb866d
commit e56dc9e294
8 changed files with 0 additions and 755 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

70
Documentation/admin-guide/nfs/fault_injection.rst
View File

@ -1,70 +0,0 @@
===================
NFS Fault Injection
===================
Fault injection is a method for forcing errors that may not normally occur, or
may be difficult to reproduce. Forcing these errors in a controlled environment
can help the developer find and fix bugs before their code is shipped in a
production system. Injecting an error on the Linux NFS server will allow us to
observe how the client reacts and if it manages to recover its state correctly.
NFSD_FAULT_INJECTION must be selected when configuring the kernel to use this
feature.
Using Fault Injection
=====================
On the client, mount the fault injection server through NFS v4.0+ and do some
work over NFS (open files, take locks, ...).
On the server, mount the debugfs filesystem to <debug_dir> and ls
<debug_dir>/nfsd. This will show a list of files that will be used for
injecting faults on the NFS server. As root, write a number n to the file
corresponding to the action you want the server to take. The server will then
process the first n items it finds. So if you want to forget 5 locks, echo '5'
to <debug_dir>/nfsd/forget_locks. A value of 0 will tell the server to forget
all corresponding items. A log message will be created containing the number
of items forgotten (check dmesg).
Go back to work on the client and check if the client recovered from the error
correctly.
Available Faults
================
forget_clients:
The NFS server keeps a list of clients that have placed a mount call. If
this list is cleared, the server will have no knowledge of who the client
is, forcing the client to reauthenticate with the server.
forget_openowners:
The NFS server keeps a list of what files are currently opened and who
they were opened by. Clearing this list will force the client to reopen
its files.
forget_locks:
The NFS server keeps a list of what files are currently locked in the VFS.
Clearing this list will force the client to reclaim its locks (files are
unlocked through the VFS as they are cleared from this list).
forget_delegations:
A delegation is used to assure the client that a file, or part of a file,
has not changed since the delegation was awarded. Clearing this list will
force the client to reacquire its delegation before accessing the file
again.
recall_delegations:
Delegations can be recalled by the server when another client attempts to
access a file. This test will notify the client that its delegation has
been revoked, forcing the client to reacquire the delegation before using
the file again.
tools/nfs/inject_faults.sh script
=================================
This script has been created to ease the fault injection process. This script
will detect the mounted debugfs directory and write to the files located there
based on the arguments passed by the user. For example, running
`inject_faults.sh forget_locks 1` as root will instruct the server to forget
one lock. Running `inject_faults forget_locks` will instruct the server to
forgetall locks.

1
Documentation/admin-guide/nfs/index.rst
View File

@ -12,4 +12,3 @@ NFS
nfs-idmapper
pnfs-block-server
pnfs-scsi-server
fault_injection

10
fs/nfsd/Kconfig
View File

@ -156,13 +156,3 @@ config NFSD_V4_SECURITY_LABEL
If you do not wish to enable fine-grained security labels SELinux or
Smack policies on NFSv4 files, say N.
config NFSD_FAULT_INJECTION
bool "NFS server manual fault injection"
depends on NFSD_V4 && DEBUG_KERNEL && DEBUG_FS && BROKEN
help
This option enables support for manually injecting faults
into the NFS server. This is intended to be used for
testing error recovery on the NFS client.
If unsure, say N.

1
fs/nfsd/Makefile
View File

@ -13,7 +13,6 @@ nfsd-y += trace.o
nfsd-y += nfssvc.o nfsctl.o nfsproc.o nfsfh.o vfs.o \
export.o auth.o lockd.o nfscache.o nfsxdr.o \
stats.o filecache.o
nfsd-$(CONFIG_NFSD_FAULT_INJECTION) += fault_inject.o
nfsd-$(CONFIG_NFSD_V2_ACL) += nfs2acl.o
nfsd-$(CONFIG_NFSD_V3) += nfs3proc.o nfs3xdr.o
nfsd-$(CONFIG_NFSD_V3_ACL) += nfs3acl.o

593
fs/nfsd/nfs4state.c
View File

@ -7253,599 +7253,6 @@ nfs4_check_open_reclaim(clientid_t *clid,
return nfs_ok;
}
#ifdef CONFIG_NFSD_FAULT_INJECTION
static inline void
put_client(struct nfs4_client *clp)
{
atomic_dec(&clp->cl_rpc_users);
}
static struct nfs4_client *
nfsd_find_client(struct sockaddr_storage *addr, size_t addr_size)
{
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
if (!nfsd_netns_ready(nn))
return NULL;
list_for_each_entry(clp, &nn->client_lru, cl_lru) {
if (memcmp(&clp->cl_addr, addr, addr_size) == 0)
return clp;
}
return NULL;
}
u64
nfsd_inject_print_clients(void)
{
struct nfs4_client *clp;
u64 count = 0;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
char buf[INET6_ADDRSTRLEN];
if (!nfsd_netns_ready(nn))
return 0;
spin_lock(&nn->client_lock);
list_for_each_entry(clp, &nn->client_lru, cl_lru) {
rpc_ntop((struct sockaddr *)&clp->cl_addr, buf, sizeof(buf));
pr_info("NFS Client: %s\n", buf);
++count;
}
spin_unlock(&nn->client_lock);
return count;
}
u64
nfsd_inject_forget_client(struct sockaddr_storage *addr, size_t addr_size)
{
u64 count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
clp = nfsd_find_client(addr, addr_size);
if (clp) {
if (mark_client_expired_locked(clp) == nfs_ok)
++count;
else
clp = NULL;
}
spin_unlock(&nn->client_lock);
if (clp)
expire_client(clp);
return count;
}
u64
nfsd_inject_forget_clients(u64 max)
{
u64 count = 0;
struct nfs4_client *clp, *next;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
list_for_each_entry_safe(clp, next, &nn->client_lru, cl_lru) {
if (mark_client_expired_locked(clp) == nfs_ok) {
list_add(&clp->cl_lru, &reaplist);
if (max != 0 && ++count >= max)
break;
}
}
spin_unlock(&nn->client_lock);
list_for_each_entry_safe(clp, next, &reaplist, cl_lru)
expire_client(clp);
return count;
}
static void nfsd_print_count(struct nfs4_client *clp, unsigned int count,
const char *type)
{
char buf[INET6_ADDRSTRLEN];
rpc_ntop((struct sockaddr *)&clp->cl_addr, buf, sizeof(buf));
printk(KERN_INFO "NFS Client: %s has %u %s\n", buf, count, type);
}
static void
nfsd_inject_add_lock_to_list(struct nfs4_ol_stateid *lst,
struct list_head *collect)
{
struct nfs4_client *clp = lst->st_stid.sc_client;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
if (!collect)
return;
lockdep_assert_held(&nn->client_lock);
atomic_inc(&clp->cl_rpc_users);
list_add(&lst->st_locks, collect);
}
static u64 nfsd_foreach_client_lock(struct nfs4_client *clp, u64 max,
struct list_head *collect,
bool (*func)(struct nfs4_ol_stateid *))
{
struct nfs4_openowner *oop;
struct nfs4_ol_stateid *stp, *st_next;
struct nfs4_ol_stateid *lst, *lst_next;
u64 count = 0;
spin_lock(&clp->cl_lock);
list_for_each_entry(oop, &clp->cl_openowners, oo_perclient) {
list_for_each_entry_safe(stp, st_next,
&oop->oo_owner.so_stateids, st_perstateowner) {
list_for_each_entry_safe(lst, lst_next,
&stp->st_locks, st_locks) {
if (func) {
if (func(lst))
nfsd_inject_add_lock_to_list(lst,
collect);
}
++count;
/*
* Despite the fact that these functions deal
* with 64-bit integers for "count", we must
* ensure that it doesn't blow up the
* clp->cl_rpc_users. Throw a warning if we
* start to approach INT_MAX here.
*/
WARN_ON_ONCE(count == (INT_MAX / 2));
if (count == max)
goto out;
}
}
}
out:
spin_unlock(&clp->cl_lock);
return count;
}
static u64
nfsd_collect_client_locks(struct nfs4_client *clp, struct list_head *collect,
u64 max)
{
return nfsd_foreach_client_lock(clp, max, collect, unhash_lock_stateid);
}
static u64
nfsd_print_client_locks(struct nfs4_client *clp)
{
u64 count = nfsd_foreach_client_lock(clp, 0, NULL, NULL);
nfsd_print_count(clp, count, "locked files");
return count;
}
u64
nfsd_inject_print_locks(void)
{
struct nfs4_client *clp;
u64 count = 0;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
if (!nfsd_netns_ready(nn))
return 0;
spin_lock(&nn->client_lock);
list_for_each_entry(clp, &nn->client_lru, cl_lru)
count += nfsd_print_client_locks(clp);
spin_unlock(&nn->client_lock);
return count;
}
static void
nfsd_reap_locks(struct list_head *reaplist)
{
struct nfs4_client *clp;
struct nfs4_ol_stateid *stp, *next;
list_for_each_entry_safe(stp, next, reaplist, st_locks) {
list_del_init(&stp->st_locks);
clp = stp->st_stid.sc_client;
nfs4_put_stid(&stp->st_stid);
put_client(clp);
}
}
u64
nfsd_inject_forget_client_locks(struct sockaddr_storage *addr, size_t addr_size)
{
unsigned int count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
clp = nfsd_find_client(addr, addr_size);
if (clp)
count = nfsd_collect_client_locks(clp, &reaplist, 0);
spin_unlock(&nn->client_lock);
nfsd_reap_locks(&reaplist);
return count;
}
u64
nfsd_inject_forget_locks(u64 max)
{
u64 count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
list_for_each_entry(clp, &nn->client_lru, cl_lru) {
count += nfsd_collect_client_locks(clp, &reaplist, max - count);
if (max != 0 && count >= max)
break;
}
spin_unlock(&nn->client_lock);
nfsd_reap_locks(&reaplist);
return count;
}
static u64
nfsd_foreach_client_openowner(struct nfs4_client *clp, u64 max,
struct list_head *collect,
void (*func)(struct nfs4_openowner *))
{
struct nfs4_openowner *oop, *next;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
u64 count = 0;
lockdep_assert_held(&nn->client_lock);
spin_lock(&clp->cl_lock);
list_for_each_entry_safe(oop, next, &clp->cl_openowners, oo_perclient) {
if (func) {
func(oop);
if (collect) {
atomic_inc(&clp->cl_rpc_users);
list_add(&oop->oo_perclient, collect);
}
}
++count;
/*
* Despite the fact that these functions deal with
* 64-bit integers for "count", we must ensure that
* it doesn't blow up the clp->cl_rpc_users. Throw a
* warning if we start to approach INT_MAX here.
*/
WARN_ON_ONCE(count == (INT_MAX / 2));
if (count == max)
break;
}
spin_unlock(&clp->cl_lock);
return count;
}
static u64
nfsd_print_client_openowners(struct nfs4_client *clp)
{
u64 count = nfsd_foreach_client_openowner(clp, 0, NULL, NULL);
nfsd_print_count(clp, count, "openowners");
return count;
}
static u64
nfsd_collect_client_openowners(struct nfs4_client *clp,
struct list_head *collect, u64 max)
{
return nfsd_foreach_client_openowner(clp, max, collect,
unhash_openowner_locked);
}
u64
nfsd_inject_print_openowners(void)
{
struct nfs4_client *clp;
u64 count = 0;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
if (!nfsd_netns_ready(nn))
return 0;
spin_lock(&nn->client_lock);
list_for_each_entry(clp, &nn->client_lru, cl_lru)
count += nfsd_print_client_openowners(clp);
spin_unlock(&nn->client_lock);
return count;
}
static void
nfsd_reap_openowners(struct list_head *reaplist)
{
struct nfs4_client *clp;
struct nfs4_openowner *oop, *next;
list_for_each_entry_safe(oop, next, reaplist, oo_perclient) {
list_del_init(&oop->oo_perclient);
clp = oop->oo_owner.so_client;
release_openowner(oop);
put_client(clp);
}
}
u64
nfsd_inject_forget_client_openowners(struct sockaddr_storage *addr,
size_t addr_size)
{
unsigned int count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
clp = nfsd_find_client(addr, addr_size);
if (clp)
count = nfsd_collect_client_openowners(clp, &reaplist, 0);
spin_unlock(&nn->client_lock);
nfsd_reap_openowners(&reaplist);
return count;
}
u64
nfsd_inject_forget_openowners(u64 max)
{
u64 count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
list_for_each_entry(clp, &nn->client_lru, cl_lru) {
count += nfsd_collect_client_openowners(clp, &reaplist,
max - count);
if (max != 0 && count >= max)
break;
}
spin_unlock(&nn->client_lock);
nfsd_reap_openowners(&reaplist);
return count;
}
static u64 nfsd_find_all_delegations(struct nfs4_client *clp, u64 max,
struct list_head *victims)
{
struct nfs4_delegation *dp, *next;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
u64 count = 0;
lockdep_assert_held(&nn->client_lock);
spin_lock(&state_lock);
list_for_each_entry_safe(dp, next, &clp->cl_delegations, dl_perclnt) {
if (victims) {
/*
* It's not safe to mess with delegations that have a
* non-zero dl_time. They might have already been broken
* and could be processed by the laundromat outside of
* the state_lock. Just leave them be.
*/
if (dp->dl_time != 0)
continue;
atomic_inc(&clp->cl_rpc_users);
WARN_ON(!unhash_delegation_locked(dp));
list_add(&dp->dl_recall_lru, victims);
}
++count;
/*
* Despite the fact that these functions deal with
* 64-bit integers for "count", we must ensure that
* it doesn't blow up the clp->cl_rpc_users. Throw a
* warning if we start to approach INT_MAX here.
*/
WARN_ON_ONCE(count == (INT_MAX / 2));
if (count == max)
break;
}
spin_unlock(&state_lock);
return count;
}
static u64
nfsd_print_client_delegations(struct nfs4_client *clp)
{
u64 count = nfsd_find_all_delegations(clp, 0, NULL);
nfsd_print_count(clp, count, "delegations");
return count;
}
u64
nfsd_inject_print_delegations(void)
{
struct nfs4_client *clp;
u64 count = 0;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
if (!nfsd_netns_ready(nn))
return 0;
spin_lock(&nn->client_lock);
list_for_each_entry(clp, &nn->client_lru, cl_lru)
count += nfsd_print_client_delegations(clp);
spin_unlock(&nn->client_lock);
return count;
}
static void
nfsd_forget_delegations(struct list_head *reaplist)
{
struct nfs4_client *clp;
struct nfs4_delegation *dp, *next;
list_for_each_entry_safe(dp, next, reaplist, dl_recall_lru) {
list_del_init(&dp->dl_recall_lru);
clp = dp->dl_stid.sc_client;
revoke_delegation(dp);
put_client(clp);
}
}
u64
nfsd_inject_forget_client_delegations(struct sockaddr_storage *addr,
size_t addr_size)
{
u64 count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
clp = nfsd_find_client(addr, addr_size);
if (clp)
count = nfsd_find_all_delegations(clp, 0, &reaplist);
spin_unlock(&nn->client_lock);
nfsd_forget_delegations(&reaplist);
return count;
}
u64
nfsd_inject_forget_delegations(u64 max)
{
u64 count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
list_for_each_entry(clp, &nn->client_lru, cl_lru) {
count += nfsd_find_all_delegations(clp, max - count, &reaplist);
if (max != 0 && count >= max)
break;
}
spin_unlock(&nn->client_lock);
nfsd_forget_delegations(&reaplist);
return count;
}
static void
nfsd_recall_delegations(struct list_head *reaplist)
{
struct nfs4_client *clp;
struct nfs4_delegation *dp, *next;
list_for_each_entry_safe(dp, next, reaplist, dl_recall_lru) {
list_del_init(&dp->dl_recall_lru);
clp = dp->dl_stid.sc_client;
trace_nfsd_deleg_recall(&dp->dl_stid.sc_stateid);
/*
* We skipped all entries that had a zero dl_time before,
* so we can now reset the dl_time back to 0. If a delegation
* break comes in now, then it won't make any difference since
* we're recalling it either way.
*/
spin_lock(&state_lock);
dp->dl_time = 0;
spin_unlock(&state_lock);
nfsd_break_one_deleg(dp);
put_client(clp);
}
}
u64
nfsd_inject_recall_client_delegations(struct sockaddr_storage *addr,
size_t addr_size)
{
u64 count = 0;
struct nfs4_client *clp;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
clp = nfsd_find_client(addr, addr_size);
if (clp)
count = nfsd_find_all_delegations(clp, 0, &reaplist);
spin_unlock(&nn->client_lock);
nfsd_recall_delegations(&reaplist);
return count;
}
u64
nfsd_inject_recall_delegations(u64 max)
{
u64 count = 0;
struct nfs4_client *clp, *next;
struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
nfsd_net_id);
LIST_HEAD(reaplist);
if (!nfsd_netns_ready(nn))
return count;
spin_lock(&nn->client_lock);
list_for_each_entry_safe(clp, next, &nn->client_lru, cl_lru) {
count += nfsd_find_all_delegations(clp, max - count, &reaplist);
if (max != 0 && ++count >= max)
break;
}
spin_unlock(&nn->client_lock);
nfsd_recall_delegations(&reaplist);
return count;
}
#endif /* CONFIG_NFSD_FAULT_INJECTION */
/*
* Since the lifetime of a delegation isn't limited to that of an open, a
* client may quite reasonably hang on to a delegation as long as it has

3
fs/nfsd/nfsctl.c
View File

@ -1534,7 +1534,6 @@ static int __init init_nfsd(void)
retval = nfsd4_init_pnfs();
if (retval)
goto out_free_slabs;
nfsd_fault_inject_init(); /* nfsd fault injection controls */
nfsd_stat_init(); /* Statistics */
retval = nfsd_drc_slab_create();
if (retval)
@ -1555,7 +1554,6 @@ out_free_lockd:
nfsd_drc_slab_free();
out_free_stat:
nfsd_stat_shutdown();
nfsd_fault_inject_cleanup();
nfsd4_exit_pnfs();
out_free_slabs:
nfsd4_free_slabs();
@ -1575,7 +1573,6 @@ static void __exit exit_nfsd(void)
nfsd_lockd_shutdown();
nfsd4_free_slabs();
nfsd4_exit_pnfs();
nfsd_fault_inject_cleanup();
unregister_filesystem(&nfsd_fs_type);
unregister_cld_notifier();
unregister_pernet_subsys(&nfsd_net_ops);

27
fs/nfsd/state.h
View File

@ -693,31 +693,4 @@ extern void nfsd4_client_record_remove(struct nfs4_client *clp);
extern int nfsd4_client_record_check(struct nfs4_client *clp);
extern void nfsd4_record_grace_done(struct nfsd_net *nn);
/* nfs fault injection functions */
#ifdef CONFIG_NFSD_FAULT_INJECTION
void nfsd_fault_inject_init(void);
void nfsd_fault_inject_cleanup(void);
u64 nfsd_inject_print_clients(void);
u64 nfsd_inject_forget_client(struct sockaddr_storage *, size_t);
u64 nfsd_inject_forget_clients(u64);
u64 nfsd_inject_print_locks(void);
u64 nfsd_inject_forget_client_locks(struct sockaddr_storage *, size_t);
u64 nfsd_inject_forget_locks(u64);
u64 nfsd_inject_print_openowners(void);
u64 nfsd_inject_forget_client_openowners(struct sockaddr_storage *, size_t);
u64 nfsd_inject_forget_openowners(u64);
u64 nfsd_inject_print_delegations(void);
u64 nfsd_inject_forget_client_delegations(struct sockaddr_storage *, size_t);
u64 nfsd_inject_forget_delegations(u64);
u64 nfsd_inject_recall_client_delegations(struct sockaddr_storage *, size_t);
u64 nfsd_inject_recall_delegations(u64);
#else /* CONFIG_NFSD_FAULT_INJECTION */
static inline void nfsd_fault_inject_init(void) {}
static inline void nfsd_fault_inject_cleanup(void) {}
#endif /* CONFIG_NFSD_FAULT_INJECTION */
#endif /* NFSD4_STATE_H */

50
tools/nfsd/inject_fault.sh
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@ -1,50 +0,0 @@
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
#
# Copyright (c) 2011 Bryan Schumaker <bjschuma@netapp.com>
#
# Script for easier NFSD fault injection
# Check that debugfs has been mounted
DEBUGFS=`cat /proc/mounts | grep debugfs`
if [ "$DEBUGFS" == "" ]; then
echo "debugfs does not appear to be mounted!"
echo "Please mount debugfs and try again"
exit 1
fi
# Check that the fault injection directory exists
DEBUGDIR=`echo $DEBUGFS | awk '{print $2}'`/nfsd
if [ ! -d "$DEBUGDIR" ]; then
echo "$DEBUGDIR does not exist"
echo "Check that your .config selects CONFIG_NFSD_FAULT_INJECTION"
exit 1
fi
function help()
{
echo "Usage $0 injection_type [count]"
echo ""
echo "Injection types are:"
ls $DEBUGDIR
exit 1
}
if [ $# == 0 ]; then
help
elif [ ! -f $DEBUGDIR/$1 ]; then
help
elif [ $# != 2 ]; then
COUNT=0
else
COUNT=$2
fi
BEFORE=`mktemp`
AFTER=`mktemp`
dmesg > $BEFORE
echo $COUNT > $DEBUGDIR/$1
dmesg > $AFTER
# Capture lines that only exist in the $AFTER file
diff $BEFORE $AFTER | grep ">"
rm -f $BEFORE $AFTER