Commit db3b5848 authored by Kiyoshi Ueda 's avatar Kiyoshi Ueda Committed by Jens Axboe
Browse files

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: default avatarJens Axboe <>
Signed-off-by: default avatarKiyoshi Ueda <>
Signed-off-by: default avatarJun'ichi Nomura <>
parent c374f127
......@@ -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 {
new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
if (!new_cfqq && !(gfp_mask & __GFP_WAIT))
goto out;
goto retry;
} else
goto out;
memset(cfqq, 0, sizeof(*cfqq));
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