diff options
| author | Kiyoshi Ueda <k-ueda@ct.jp.nec.com> | 2005-06-17 18:15:10 +0400 |
|---|---|---|
| committer | Jens Axboe <axboe@suse.de> | 2005-06-17 18:15:10 +0400 |
| commit | db3b5848ea6440968fcdd29b80514d0de044bb7c (patch) | |
| tree | 75d3356743362570b7e6f94696f37fd4b1c9ce2f /drivers | |
| parent | c374f127e4ff17a318b9ae95a5bf65f370c2d0b1 (diff) | |
| download | linux-db3b5848ea6440968fcdd29b80514d0de044bb7c.tar.xz | |
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/block/cfq-iosched.c | 9 |
1 files 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 @@ 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)); |