From db3b5848ea6440968fcdd29b80514d0de044bb7c Mon Sep 17 00:00:00 2001
From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Date: Fri, 17 Jun 2005 16:15:10 +0200
Subject: [PATCH] When cfq I/O scheduler is selected, get_request() in
__make_request() calls __cfq_get_queue(). __cfq_get_queue() finds an
existing queue (struct cfq_queue) of the current process for the device and
returns it. If it's not found, __cfq_get_queue() creates and returns a new
one if __cfq_get_queue() is called with __GFP_WAIT flag, or __cfq_get_queue()
returns NULL (this means that get_request() fails) if no __GFP_WAIT flag.
On the other hand, in __make_request(), get_request() is called without
__GFP_WAIT flag at the first time. Thus, the get_request() fails when there is
no existing queue, typically when it's called for the first I/O request of the
process to the device.
Though it will be followed by get_request_wait() for general case,
__make_request() will just end the I/O with an error (EWOULDBLOCK) when the
request was for read-ahead.
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
---
drivers/block/cfq-iosched.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/block/cfq-iosched.c b/drivers/block/cfq-iosched.c
index 0ef7a0065ece..2210bacad56a 100644
--- a/drivers/block/cfq-iosched.c
+++ b/drivers/block/cfq-iosched.c
@@ -1202,13 +1202,16 @@ __cfq_get_queue(struct cfq_data *cfqd, unsigned long key, int gfp_mask)
if (new_cfqq) {
cfqq = new_cfqq;
new_cfqq = NULL;
- } else if (gfp_mask & __GFP_WAIT) {
+ } else {
spin_unlock_irq(cfqd->queue->queue_lock);
new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
spin_lock_irq(cfqd->queue->queue_lock);
+
+ if (!new_cfqq && !(gfp_mask & __GFP_WAIT))
+ goto out;
+
goto retry;
- } else
- goto out;
+ }
memset(cfqq, 0, sizeof(*cfqq));
--
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