Re: [PATCH V11 07/19] fs/buffer.c: use bvec iterator to truncate the bio

Christoph Hellwig
2018-11-22T10:58:54Z

Btw, given that this is the last user of bvec_last_segment after my
other patches I think we should kill bvec_last_segment and do something
like this here:

diff --git a/fs/buffer.c b/fs/buffer.c
index fa37ad52e962..af5e135d2b83 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2981,6 +2981,14 @@ static void end_bio_bh_io_sync(struct bio *bio)
bio_put(bio);
}

+static void zero_trailing_sectors(struct bio_vec *bvec, unsigned bytes)
+{
+ unsigned last_page = (bvec->bv_offset + bvec->bv_len - 1) >> PAGE_SHIFT;
+
+ zero_user(nth_page(bvec->bv_page, last_page),
+ bvec->bv_offset % PAGE_SIZE + bvec->bv_len, bytes);
+}
+
/*
* This allows us to do IO even on the odd last sectors
* of a device, even if the block size is some multiple
@@ -3031,13 +3039,8 @@ void guard_bio_eod(int op, struct bio *bio)
bvec->bv_len -= truncated_bytes;

/* ..and clear the end of the buffer for reads */
- if (op == REQ_OP_READ) {
- struct bio_vec bv;
-
- bvec_last_segment(bvec, &bv);
- zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
- truncated_bytes);
- }
+ if (op == REQ_OP_READ)
+ zero_trailing_sectors(bvec, truncated_bytes);
}

static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,