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[PATCH v3 11/49] btrfs: avoid access to .bi_vcnt directly

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  [PATCH v3 11/49] btrfs: avoid access to .bi_vcnt directly Ming Lei <ming.lei@redhat.com> - 2017-08-08 10:50 +0200
    Re: [PATCH v3 11/49] btrfs: avoid access to .bi_vcnt directly Christoph Hellwig <hch@infradead.org> - 2017-08-10 13:40 +0200

#1706167 — [PATCH v3 11/49] btrfs: avoid access to .bi_vcnt directly

BTRFS uses bio->bi_vcnt to figure out page numbers, this
way becomes not correct once we start to enable multipage
bvec.

So use bio_for_each_segment_all() to do that instead.

Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-btrfs@vger.kernel.org
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 fs/btrfs/extent_io.c | 20 ++++++++++++++++----
 fs/btrfs/extent_io.h |  2 +-
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 0aff9b278c19..0e7367817b92 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2258,7 +2258,7 @@ int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
 	return 0;
 }
 
-bool btrfs_check_repairable(struct inode *inode, struct bio *failed_bio,
+bool btrfs_check_repairable(struct inode *inode, unsigned failed_bio_pages,
 			   struct io_failure_record *failrec, int failed_mirror)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
@@ -2282,7 +2282,7 @@ bool btrfs_check_repairable(struct inode *inode, struct bio *failed_bio,
 	 *	a) deliver good data to the caller
 	 *	b) correct the bad sectors on disk
 	 */
-	if (failed_bio->bi_vcnt > 1) {
+	if (failed_bio_pages > 1) {
 		/*
 		 * to fulfill b), we need to know the exact failing sectors, as
 		 * we don't want to rewrite any more than the failed ones. thus,
@@ -2355,6 +2355,17 @@ struct bio *btrfs_create_repair_bio(struct inode *inode, struct bio *failed_bio,
 	return bio;
 }
 
+static unsigned int get_bio_pages(struct bio *bio)
+{
+	unsigned i;
+	struct bio_vec *bv;
+
+	bio_for_each_segment_all(bv, bio, i)
+		;
+
+	return i;
+}
+
 /*
  * this is a generic handler for readpage errors (default
  * readpage_io_failed_hook). if other copies exist, read those and write back
@@ -2375,6 +2386,7 @@ static int bio_readpage_error(struct bio *failed_bio, u64 phy_offset,
 	int read_mode = 0;
 	blk_status_t status;
 	int ret;
+	unsigned failed_bio_pages = get_bio_pages(failed_bio);
 
 	BUG_ON(bio_op(failed_bio) == REQ_OP_WRITE);
 
@@ -2382,13 +2394,13 @@ static int bio_readpage_error(struct bio *failed_bio, u64 phy_offset,
 	if (ret)
 		return ret;
 
-	if (!btrfs_check_repairable(inode, failed_bio, failrec,
+	if (!btrfs_check_repairable(inode, failed_bio_pages, failrec,
 				    failed_mirror)) {
 		free_io_failure(failure_tree, tree, failrec);
 		return -EIO;
 	}
 
-	if (failed_bio->bi_vcnt > 1)
+	if (failed_bio_pages > 1)
 		read_mode |= REQ_FAILFAST_DEV;
 
 	phy_offset >>= inode->i_sb->s_blocksize_bits;
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 4f030912f3ef..300ee10f39f2 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -539,7 +539,7 @@ void btrfs_free_io_failure_record(struct btrfs_inode *inode, u64 start,
 		u64 end);
 int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
 				struct io_failure_record **failrec_ret);
-bool btrfs_check_repairable(struct inode *inode, struct bio *failed_bio,
+bool btrfs_check_repairable(struct inode *inode, unsigned failed_bio_pages,
 			    struct io_failure_record *failrec, int fail_mirror);
 struct bio *btrfs_create_repair_bio(struct inode *inode, struct bio *failed_bio,
 				    struct io_failure_record *failrec,
-- 
2.9.4

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#1708467

> +static unsigned int get_bio_pages(struct bio *bio)
> +{
> +	unsigned i;
> +	struct bio_vec *bv;
> +
> +	bio_for_each_segment_all(bv, bio, i)
> +		;
> +
> +	return i;
> +}

s/get_bio_pages/bio_nr_pages/ ?

Also this seems like a useful helper for bio.h

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