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| author | NeilBrown <neilb@suse.de> | 2007-09-25 12:35:59 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@carl.home.kernel.dk> | 2007-10-10 09:25:56 +0200 |
| commit | 5705f7021748a69d84d6567e68e8851dab551464 (patch) | |
| tree | 5a6dbc8fc6055c0334f4a97540e36a7844b9c482 /Documentation/block | |
| parent | 9dfa52831e96194b8649613e3131baa2c109f7dc (diff) | |
| download | linux-5705f7021748a69d84d6567e68e8851dab551464.tar.gz | |
Introduce rq_for_each_segment replacing rq_for_each_bio
Every usage of rq_for_each_bio wraps a usage of bio_for_each_segment, so these can be combined into rq_for_each_segment. We define "struct req_iterator" to hold the 'bio' and 'index' that are needed for the double iteration. Signed-off-by: Neil Brown <neilb@suse.de> Various compile fixes by me... Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'Documentation/block')
| -rw-r--r-- | Documentation/block/biodoc.txt | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt index 8af392fc6ef0..dc3f49e3e539 100644 --- a/Documentation/block/biodoc.txt +++ b/Documentation/block/biodoc.txt @@ -477,9 +477,9 @@ With this multipage bio design: the same bi_io_vec array, but with the index and size accordingly modified) - A linked list of bios is used as before for unrelated merges (*) - this avoids reallocs and makes independent completions easier to handle. -- Code that traverses the req list needs to make a distinction between - segments of a request (bio_for_each_segment) and the distinct completion - units/bios (rq_for_each_bio). +- Code that traverses the req list can find all the segments of a bio + by using rq_for_each_segment. This handles the fact that a request + has multiple bios, each of which can have multiple segments. - Drivers which can't process a large bio in one shot can use the bi_idx field to keep track of the next bio_vec entry to process. (e.g a 1MB bio_vec needs to be handled in max 128kB chunks for IDE) @@ -664,14 +664,14 @@ in lvm or md. 3.2.1 Traversing segments and completion units in a request -The macros bio_for_each_segment() and rq_for_each_bio() should be used for -traversing the bios in the request list (drivers should avoid directly -trying to do it themselves). Using these helpers should also make it easier -to cope with block changes in the future. +The macro rq_for_each_segment() should be used for traversing the bios +in the request list (drivers should avoid directly trying to do it +themselves). Using these helpers should also make it easier to cope +with block changes in the future. - rq_for_each_bio(bio, rq) - bio_for_each_segment(bio_vec, bio, i) - /* bio_vec is now current segment */ + struct req_iterator iter; + rq_for_each_segment(bio_vec, rq, iter) + /* bio_vec is now current segment */ I/O completion callbacks are per-bio rather than per-segment, so drivers that traverse bio chains on completion need to keep that in mind. Drivers |