Thread (25 messages) 25 messages, 3 authors, 2019-01-22
STALE2701d REVIEWED: 1 (0M)
Revisions (7)
  1. v8 [diff vs current]
  2. v9 [diff vs current]
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  5. v12 [diff vs current]
  6. v14 current
  7. v15 [diff vs current]

[PATCH V14 08/18] block: introduce mp_bvec_last_segment()

From: Ming Lei <hidden>
Date: 2019-01-21 08:20:44
Also in: dm-devel, linux-bcache, linux-block, linux-btrfs, linux-ext4, linux-fsdevel, linux-mm, linux-xfs, lkml
Subsystem: the rest · Maintainer: Linus Torvalds

BTRFS and guard_bio_eod() need to get the last singlepage segment
from one multipage bvec, so introduce this helper to make them happy.

Reviewed-by: Omar Sandoval <redacted>
Signed-off-by: Ming Lei <redacted>
---
 include/linux/bvec.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 0ae729b1c9fe..21f76bad7be2 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -131,4 +131,26 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
 	.bi_bvec_done	= 0,						\
 }
 
+/*
+ * Get the last single-page segment from the multi-page bvec and store it
+ * in @seg
+ */
+static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
+					struct bio_vec *seg)
+{
+	unsigned total = bvec->bv_offset + bvec->bv_len;
+	unsigned last_page = (total - 1) / PAGE_SIZE;
+
+	seg->bv_page = nth_page(bvec->bv_page, last_page);
+
+	/* the whole segment is inside the last page */
+	if (bvec->bv_offset >= last_page * PAGE_SIZE) {
+		seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
+		seg->bv_len = bvec->bv_len;
+	} else {
+		seg->bv_offset = 0;
+		seg->bv_len = total - last_page * PAGE_SIZE;
+	}
+}
+
 #endif /* __LINUX_BVEC_ITER_H */
-- 
2.9.5
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