From: Bart Van Assche <bvanassche@acm.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
Ming Lei <ming.lei@redhat.com>,
Alexander Potapenko <glider@google.com>,
Bart Van Assche <bvanassche@acm.org>,
Christoph Hellwig <hch@infradead.org>
Subject: [PATCH v3 3/4] block: Document the bio_vec properties
Date: Mon, 18 May 2020 21:07:36 -0700 [thread overview]
Message-ID: <20200519040737.4531-4-bvanassche@acm.org> (raw)
In-Reply-To: <20200519040737.4531-1-bvanassche@acm.org>
Since it is nontrivial that nth_page() does not have to be used for a
bio_vec, document this.
CC: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
include/linux/bvec.h | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index a81c13ac1972..ac0c7299d5b8 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -12,8 +12,17 @@
#include <linux/errno.h>
#include <linux/mm.h>
-/*
- * was unsigned short, but we might as well be ready for > 64kB I/O pages
+/**
+ * struct bio_vec - a contiguous range of physical memory addresses
+ * @bv_page: First page associated with the address range.
+ * @bv_len: Number of bytes in the address range.
+ * @bv_offset: Start of the address range relative to the start of @bv_page.
+ *
+ * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
+ *
+ * nth_page(@bv_page, n) == @bv_page + n
+ *
+ * This holds because page_is_mergeable() checks the above property.
*/
struct bio_vec {
struct page *bv_page;
next prev parent reply other threads:[~2020-05-19 4:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-19 4:07 [PATCH v3 0/4] Block layer patches for kernel v5.8 Bart Van Assche
2020-05-19 4:07 ` [PATCH v3 1/4] block: Fix type of first compat_put_{,u}long() argument Bart Van Assche
2020-05-19 8:34 ` Johannes Thumshirn
2020-05-19 4:07 ` [PATCH v3 2/4] bio.h: Declare the arguments of the bio iteration functions const Bart Van Assche
2020-05-19 8:35 ` Johannes Thumshirn
2020-05-19 4:07 ` Bart Van Assche [this message]
2020-05-19 15:21 ` [PATCH v3 3/4] block: Document the bio_vec properties Christoph Hellwig
2020-05-19 4:07 ` [PATCH v3 4/4] null_blk: Zero-initialize read buffers in non-memory-backed mode Bart Van Assche
2020-05-19 15:40 ` [PATCH v3 0/4] Block layer patches for kernel v5.8 Jens Axboe
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