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Subject[patch 034/100] dm: preserve bi_io_vec when resubmitting bios
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Mikulas Patocka <mpatocka@redhat.com>

upstream commit: a920f6b3accc77d9dddbc98a7426be23ee479625

Device mapper saves and restores various fields in the bio, but it doesn't save
bi_io_vec. If the device driver modifies this after a partially successful
request, dm-raid1 and dm-multipath may attempt to resubmit a bio that has
bi_size inconsistent with the size of vector.

To make requests resubmittable in dm-raid1 and dm-multipath, we must save
and restore the bio vector as well.

To reduce the memory overhead involved in this, we do not save the pages in a
vector and use a 16-bit field size if the page size is less than 65536.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
drivers/md/dm-bio-record.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)

--- a/drivers/md/dm-bio-record.h
+++ b/drivers/md/dm-bio-record.h
@@ -16,30 +16,56 @@
* functions in this file help the target record and restore the
* original bio state.
*/
+
+struct dm_bio_vec_details {
+#if PAGE_SIZE < 65536
+ __u16 bv_len;
+ __u16 bv_offset;
+#else
+ unsigned bv_len;
+ unsigned bv_offset;
+#endif
+};
+
struct dm_bio_details {
sector_t bi_sector;
struct block_device *bi_bdev;
unsigned int bi_size;
unsigned short bi_idx;
unsigned long bi_flags;
+ struct dm_bio_vec_details bi_io_vec[BIO_MAX_PAGES];
};

static inline void dm_bio_record(struct dm_bio_details *bd, struct bio *bio)
{
+ unsigned i;
+
bd->bi_sector = bio->bi_sector;
bd->bi_bdev = bio->bi_bdev;
bd->bi_size = bio->bi_size;
bd->bi_idx = bio->bi_idx;
bd->bi_flags = bio->bi_flags;
+
+ for (i = 0; i < bio->bi_vcnt; i++) {
+ bd->bi_io_vec[i].bv_len = bio->bi_io_vec[i].bv_len;
+ bd->bi_io_vec[i].bv_offset = bio->bi_io_vec[i].bv_offset;
+ }
}

static inline void dm_bio_restore(struct dm_bio_details *bd, struct bio *bio)
{
+ unsigned i;
+
bio->bi_sector = bd->bi_sector;
bio->bi_bdev = bd->bi_bdev;
bio->bi_size = bd->bi_size;
bio->bi_idx = bd->bi_idx;
bio->bi_flags = bd->bi_flags;
+
+ for (i = 0; i < bio->bi_vcnt; i++) {
+ bio->bi_io_vec[i].bv_len = bd->bi_io_vec[i].bv_len;
+ bio->bi_io_vec[i].bv_offset = bd->bi_io_vec[i].bv_offset;
+ }
}

#endif


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