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[XFS] Convert l_flushsema to a sv_t

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The l_flushsema doesn't exactly have completion semantics, nor mutex
semantics. It's used as a list of tasks which are waiting to be notified
that a flush has completed. It was also being used in a way that was
potentially racy, depending on the semaphore implementation.

By using a sv_t instead of a semaphore we avoid the need for a separate
counter, since we know we just need to wake everything on the queue.

Original waitqueue implementation from Matthew Wilcox. Cleanup and
conversion to sv_t by Christoph Hellwig.

SGI-PV: 981507
SGI-Modid: xfs-linux-melb:xfs-kern:31059a

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
This commit is contained in:
Matthew Wilcox 2008-05-19 16:34:27 +10:00 committed by Niv Sardi
parent d729eae893
commit d748c62367
2 changed files with 15 additions and 20 deletions
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29
fs/xfs/xfs_log.c
View File

@ -1232,7 +1232,7 @@ xlog_alloc_log(xfs_mount_t *mp,
spin_lock_init(&log->l_icloglock);
spin_lock_init(&log->l_grant_lock);
initnsema(&log->l_flushsema, 0, "ic-flush");
sv_init(&log->l_flush_wait, 0, "flush_wait");
/* log record size must be multiple of BBSIZE; see xlog_rec_header_t */
ASSERT((XFS_BUF_SIZE(bp) & BBMASK) == 0);
@ -1577,7 +1577,6 @@ xlog_dealloc_log(xlog_t *log)
kmem_free(iclog);
iclog = next_iclog;
}
freesema(&log->l_flushsema);
spinlock_destroy(&log->l_icloglock);
spinlock_destroy(&log->l_grant_lock);
@ -2101,6 +2100,7 @@ xlog_state_do_callback(
int funcdidcallbacks; /* flag: function did callbacks */
int repeats; /* for issuing console warnings if
* looping too many times */
int wake = 0;
spin_lock(&log->l_icloglock);
first_iclog = iclog = log->l_iclog;
@ -2282,15 +2282,13 @@ xlog_state_do_callback(
}
#endif
flushcnt = 0;
if (log->l_iclog->ic_state & (XLOG_STATE_ACTIVE|XLOG_STATE_IOERROR)) {
flushcnt = log->l_flushcnt;
log->l_flushcnt = 0;
}
if (log->l_iclog->ic_state & (XLOG_STATE_ACTIVE|XLOG_STATE_IOERROR))
wake = 1;
spin_unlock(&log->l_icloglock);
while (flushcnt--)
vsema(&log->l_flushsema);
} /* xlog_state_do_callback */
if (wake)
sv_broadcast(&log->l_flush_wait);
}
/*
@ -2388,16 +2386,15 @@ restart:
}
iclog = log->l_iclog;
if (! (iclog->ic_state == XLOG_STATE_ACTIVE)) {
log->l_flushcnt++;
spin_unlock(&log->l_icloglock);
if (iclog->ic_state != XLOG_STATE_ACTIVE) {
xlog_trace_iclog(iclog, XLOG_TRACE_SLEEP_FLUSH);
XFS_STATS_INC(xs_log_noiclogs);
/* Ensure that log writes happen */
psema(&log->l_flushsema, PINOD);
/* Wait for log writes to have flushed */
sv_wait(&log->l_flush_wait, 0, &log->l_icloglock, 0);
goto restart;
}
ASSERT(iclog->ic_state == XLOG_STATE_ACTIVE);
head = &iclog->ic_header;
atomic_inc(&iclog->ic_refcnt); /* prevents sync */

6
fs/xfs/xfs_log_priv.h
View File

@ -423,10 +423,8 @@ typedef struct log {
int l_logBBsize; /* size of log in BB chunks */
/* The following block of fields are changed while holding icloglock */
sema_t l_flushsema ____cacheline_aligned_in_smp;
/* iclog flushing semaphore */
int l_flushcnt; /* # of procs waiting on this
* sema */
sv_t l_flush_wait ____cacheline_aligned_in_smp;
/* waiting for iclog flush */
int l_covered_state;/* state of "covering disk
* log entries" */
xlog_in_core_t *l_iclog; /* head log queue */