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Subject[PATCH 2/9] block: Add bio_advance()
Date
This is prep work for immutable bio vecs; we first want to centralize
where bvecs are modified.

Next two patches convert some existing code to use this function.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
---
fs/bio.c | 41 +++++++++++++++++++++++++++++++++++++++++
include/linux/bio.h | 2 ++
2 files changed, 43 insertions(+)

diff --git a/fs/bio.c b/fs/bio.c
index 244007f..a539664 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -719,6 +719,47 @@ int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
}
EXPORT_SYMBOL(bio_add_page);

+/**
+ * bio_advance - increment/complete a bio by some number of bytes
+ * @bio: bio to advance
+ * @bytes: number of bytes to complete
+ *
+ * This updates bi_sector, bi_size and bi_idx; if the number of bytes to
+ * complete doesn't align with a bvec boundary, then bv_len and bv_offset will
+ * be updated on the last bvec as well.
+ *
+ * @bio will then represent the remaining, uncompleted portion of the io.
+ */
+void bio_advance(struct bio *bio, unsigned bytes)
+{
+ if (bio_integrity(bio))
+ bio_integrity_advance(bio, bytes);
+
+ bio->bi_sector += bytes >> 0;
+ bio->bi_size -= bytes;
+
+ if (!bio->bi_size)
+ return;
+
+ while (bytes) {
+ if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
+ printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
+ __func__, bio->bi_idx, bio->bi_vcnt);
+ break;
+ }
+
+ if (bytes >= bio_iovec(bio)->bv_len) {
+ bytes -= bio_iovec(bio)->bv_len;
+ bio->bi_idx++;
+ } else {
+ bio_iovec(bio)->bv_len -= bytes;
+ bio_iovec(bio)->bv_offset += bytes;
+ bytes = 0;
+ }
+ }
+}
+EXPORT_SYMBOL(bio_advance);
+
struct bio_map_data {
struct bio_vec *iovecs;
struct sg_iovec *sgvecs;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 7873465..6763cdf 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -248,6 +248,8 @@ extern void bio_endio(struct bio *, int);
struct request_queue;
extern int bio_phys_segments(struct request_queue *, struct bio *);

+void bio_advance(struct bio *, unsigned);
+
extern void bio_init(struct bio *);
extern void bio_reset(struct bio *);

--
1.7.12


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