Narasimhamurthy Giridhar wrote:
> Hi all
> In __make_request(), there is a statement :
>
> el_ret = elevator->elevator_merge_fn(....);
a function pointer!
Quick look through LXR!! (I don't know what it is :-)
blkdev.h
--------
12 struct elevator_s;
13 typedef struct elevator_s elevator_t;
elevator.h
----------
8 typedef int (elevator_merge_fn) (request_queue_t *, struct request **,
9 struct list_head *, struct buffer_head *, int, int);
15 struct elevator_s
16 {
17 int read_latency;
18 int write_latency;
19
20 elevator_merge_fn *elevator_merge_fn;
21 elevator_merge_cleanup_fn *elevator_merge_cleanup_fn;
22 elevator_merge_req_fn *elevator_merge_req_fn;
23
24 unsigned int queue_ID;
25 };
84 #define ELEVATOR_NOOP \
85 ((elevator_t) { \
86 0, /* read_latency */ \
87 0, /* write_latency */ \
88 \
89 elevator_noop_merge, /* elevator_merge_fn */ \
90 elevator_noop_merge_cleanup, /* elevator_merge_cleanup_fn */\
91 elevator_noop_merge_req, /* elevator_merge_req_fn */ \
92 })
93
94 #define ELEVATOR_LINUS \
95 ((elevator_t) { \
96 8192, /* read passovers */ \
97 16384, /* write passovers */ \
98 \
99 elevator_linus_merge, /* elevator_merge_fn */ \
100 elevator_linus_merge_cleanup, /* elevator_merge_cleanup_fn */\
101 elevator_linus_merge_req, /* elevator_merge_req_fn */ \
102 })
103
elevator_noop_merge
-------------------
Defined as a function in:
* drivers/block/elevator.c, line 144
elevator_linus_merge
--------------------
Defined as a function in:
* drivers/block/elevator.c, line 78
BTW
What is an elevator?
Regards,
Sourav
>
> Where is the definition of this elevator_merge_fn ?
> How does it work ?
> Thanx
> Narasimhamurthy Giri, Clemson University Computer Science Dept.
> -------------------------------------------------------------------------------
> Judge not lest ye be judged yourself.
> -------------------------------------------------------------------------------
>
>
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>
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