From: Kiyoshi Ueda Date: Fri, 17 Jun 2005 14:15:10 +0000 (+0200) Subject: When cfq I/O scheduler is selected, get_request() in __make_request() calls X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=db3b5848ea6440968fcdd29b80514d0de044bb7c;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git 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 Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura --- 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 @@ retry: 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));