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author | J. Bruce Fields <bfields@citi.umich.edu> | 2008-03-18 19:00:19 -0400 |
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committer | J. Bruce Fields <bfields@citi.umich.edu> | 2008-09-29 18:13:10 -0400 |
commit | c8ab5f2a13fb41a878863c61a1e27d78f1844b5e (patch) | |
tree | 869ce6a2a51581d09011aeb5e804b0d1ab39a7b9 /fs/lockd/svc.c | |
parent | 8fafa90082ab18859d97627fc454edf12f7efbff (diff) | |
download | linux-stable-c8ab5f2a13fb41a878863c61a1e27d78f1844b5e.tar.gz linux-stable-c8ab5f2a13fb41a878863c61a1e27d78f1844b5e.tar.bz2 linux-stable-c8ab5f2a13fb41a878863c61a1e27d78f1844b5e.zip |
lockd: don't depend on lockd main loop to end grace
End lockd's grace period using schedule_delayed_work() instead of a
check on every pass through the main loop.
After a later patch, we'll depend on lockd to end its grace period even
if it's not currently handling requests; so it shouldn't depend on being
woken up from the main loop to do so.
Also, Nakano Hiroaki (who independently produced a similar patch)
noticed that the current behavior is buggy in the face of jiffies
wraparound:
"lockd uses time_before() to determine whether the grace period
has expired. This would seem to be enough to avoid timer
wrap-around issues, but, unfortunately, that is not the case.
The time_* family of comparison functions can be safely used to
compare jiffies relatively close in time, but they stop working
after approximately LONG_MAX/2 ticks. nfsd can suffer this
problem because the time_before() comparison in lockd() is not
performed until the first request comes in, which means that if
there is no lockd traffic for more than LONG_MAX/2 ticks we are
screwed.
"The implication of this is that once time_before() starts
misbehaving any attempt from a NFS client to execute fcntl()
will be received with a NLM_LCK_DENIED_GRACE_PERIOD message for
25 days (assuming HZ=1000). In other words, the 50 seconds grace
period could turn into a grace period of 50 days or more.
"Note: This bug was analyzed independently by Oda-san
<oda@valinux.co.jp> and myself."
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Nakano Hiroaki <nakano.hiroaki@oss.ntt.co.jp>
Cc: Itsuro Oda <oda@valinux.co.jp>
Diffstat (limited to 'fs/lockd/svc.c')
-rw-r--r-- | fs/lockd/svc.c | 24 |
1 files changed, 13 insertions, 11 deletions
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c index bdc607bb25e9..f345ef7fb8ae 100644 --- a/fs/lockd/svc.c +++ b/fs/lockd/svc.c @@ -97,15 +97,20 @@ unsigned long get_nfs_grace_period(void) } EXPORT_SYMBOL(get_nfs_grace_period); -static unsigned long set_grace_period(void) +static void grace_ender(struct work_struct *not_used) { - nlmsvc_grace_period = 1; - return get_nfs_grace_period() + jiffies; + nlmsvc_grace_period = 0; } -static inline void clear_grace_period(void) +static DECLARE_DELAYED_WORK(grace_period_end, grace_ender); + +static void set_grace_period(void) { - nlmsvc_grace_period = 0; + unsigned long grace_period = get_nfs_grace_period() + jiffies; + + nlmsvc_grace_period = 1; + cancel_delayed_work_sync(&grace_period_end); + schedule_delayed_work(&grace_period_end, grace_period); } /* @@ -116,7 +121,6 @@ lockd(void *vrqstp) { int err = 0, preverr = 0; struct svc_rqst *rqstp = vrqstp; - unsigned long grace_period_expire; /* try_to_freeze() is called from svc_recv() */ set_freezable(); @@ -139,7 +143,7 @@ lockd(void *vrqstp) nlm_timeout = LOCKD_DFLT_TIMEO; nlmsvc_timeout = nlm_timeout * HZ; - grace_period_expire = set_grace_period(); + set_grace_period(); /* * The main request loop. We don't terminate until the last @@ -153,16 +157,13 @@ lockd(void *vrqstp) flush_signals(current); if (nlmsvc_ops) { nlmsvc_invalidate_all(); - grace_period_expire = set_grace_period(); + set_grace_period(); } continue; } timeout = nlmsvc_retry_blocked(); - if (time_before(grace_period_expire, jiffies)) - clear_grace_period(); - /* * Find a socket with data available and call its * recvfrom routine. @@ -189,6 +190,7 @@ lockd(void *vrqstp) svc_process(rqstp); } flush_signals(current); + cancel_delayed_work_sync(&grace_period_end); if (nlmsvc_ops) nlmsvc_invalidate_all(); nlm_shutdown_hosts(); |