diff options
Diffstat (limited to 'Documentation/block/biodoc.txt')
| -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 |