rq->raw_data_len introduced for block layer padding and draining
(commit 6b00769fe1502b4ad97bb327ef7ac971b208bfb5) broke residual byte
count handling. Block drivers modify rq->data_len to notify residual
byte count to the block layer which blindly reported unmodified
rq->raw_data_len to userland.
To keep block drivers dealing only with rq->data_len, this should be
handled inside block layer. However, how much extra buffer was
appened is lost after rq->data_len is modified.
This patch replaces rq->raw_data_len with rq->extra_len and add
blk_rq_raw_data_len() helper to calculate raw data size from
rq->data_len and rq->extra_len. The helper returns correct raw
residual byte count when called on a rq whose data_len is modified to
carry residual byte count.
This problem was reported and diagnosed by Mike Galbraith.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
---
Comments updated compared to the previous version.
block/blk-core.c | 3 +--
block/blk-map.c | 2 +-
block/blk-merge.c | 1 +
block/blk-settings.c | 4 ++++
block/bsg.c | 8 ++++----
block/scsi_ioctl.c | 4 ++--
drivers/ata/libata-scsi.c | 3 ++-
include/linux/blkdev.h | 8 +++++++-
8 files changed, 22 insertions(+), 11 deletions(-)
Index: work/block/blk-core.c
===================================================================
--- work.orig/block/blk-core.c
+++ work/block/blk-core.c
@@ -127,7 +127,7 @@ void rq_init(struct request_queue *q, st
rq->nr_hw_segments = 0;
rq->ioprio = 0;
rq->special = NULL;
- rq->raw_data_len = 0;
+ rq->extra_len = 0;
rq->buffer = NULL;
rq->tag = -1;
rq->errors = 0;
@@ -2016,7 +2016,6 @@ void blk_rq_bio_prep(struct request_queu
rq->hard_cur_sectors = rq->current_nr_sectors;
rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
rq->buffer = bio_data(bio);
- rq->raw_data_len = bio->bi_size;
rq->data_len = bio->bi_size;
rq->bio = rq->biotail = bio;
Index: work/block/blk-map.c
===================================================================
--- work.orig/block/blk-map.c
+++ work/block/blk-map.c
@@ -19,7 +19,6 @@ int blk_rq_append_bio(struct request_que
rq->biotail->bi_next = bio;
rq->biotail = bio;
- rq->raw_data_len += bio->bi_size;
rq->data_len += bio->bi_size;
}
return 0;
@@ -156,6 +155,7 @@ int blk_rq_map_user(struct request_queue
bio->bi_io_vec[bio->bi_vcnt - 1].bv_len += pad_len;
bio->bi_size += pad_len;
rq->data_len += pad_len;
+ rq->extra_len += pad_len;
}
rq->buffer = rq->data = NULL;
Index: work/block/blk-merge.c
===================================================================
--- work.orig/block/blk-merge.c
+++ work/block/blk-merge.c
@@ -232,6 +232,7 @@ new_segment:
(PAGE_SIZE - 1));
nsegs++;
rq->data_len += q->dma_drain_size;
+ rq->extra_len += q->dma_drain_size;
}
if (sg)
Index: work/block/bsg.c
===================================================================
--- work.orig/block/bsg.c
+++ work/block/bsg.c
@@ -437,14 +437,14 @@ static int blk_complete_sgv4_hdr_rq(stru
}
if (rq->next_rq) {
- hdr->dout_resid = rq->raw_data_len;
- hdr->din_resid = rq->next_rq->raw_data_len;
+ hdr->dout_resid = blk_rq_raw_data_len(rq);
+ hdr->din_resid = blk_rq_raw_data_len(rq->next_rq);
blk_rq_unmap_user(bidi_bio);
blk_put_request(rq->next_rq);
} else if (rq_data_dir(rq) == READ)
- hdr->din_resid = rq->raw_data_len;
+ hdr->din_resid = blk_rq_raw_data_len(rq);
else
- hdr->dout_resid = rq->raw_data_len;
+ hdr->dout_resid = blk_rq_raw_data_len(rq);
/*
* If the request generated a negative error number, return it
Index: work/block/scsi_ioctl.c
===================================================================
--- work.orig/block/scsi_ioctl.c
+++ work/block/scsi_ioctl.c
@@ -266,7 +266,7 @@ static int blk_complete_sghdr_rq(struct
hdr->info = 0;
if (hdr->masked_status || hdr->host_status || hdr->driver_status)
hdr->info |= SG_INFO_CHECK;
- hdr->resid = rq->raw_data_len;
+ hdr->resid = blk_rq_raw_data_len(rq);
hdr->sb_len_wr = 0;
if (rq->sense_len && hdr->sbp) {
@@ -528,8 +528,8 @@ static int __blk_send_generic(struct req
rq = blk_get_request(q, WRITE, __GFP_WAIT);
rq->cmd_type = REQ_TYPE_BLOCK_PC;
rq->data = NULL;
- rq->raw_data_len = 0;
rq->data_len = 0;
+ rq->extra_len = 0;
rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
memset(rq->cmd, 0, sizeof(rq->cmd));
rq->cmd[0] = cmd;
Index: work/drivers/ata/libata-scsi.c
===================================================================
--- work.orig/drivers/ata/libata-scsi.c
+++ work/drivers/ata/libata-scsi.c
@@ -2549,7 +2549,8 @@ static unsigned int atapi_xlat(struct at
* want to set it properly, and for DMA where it is
* effectively meaningless.
*/
- nbytes = min(scmd->request->raw_data_len, (unsigned int)63 * 1024);
+ nbytes = min(blk_rq_raw_data_len(scmd->request),
+ (unsigned int)63 * 1024);
/* Most ATAPI devices which honor transfer chunk size don't
* behave according to the spec when odd chunk size which
Index: work/include/linux/blkdev.h
===================================================================
--- work.orig/include/linux/blkdev.h
+++ work/include/linux/blkdev.h
@@ -216,8 +216,8 @@ struct request {
unsigned int cmd_len;
unsigned char cmd[BLK_MAX_CDB];
- unsigned int raw_data_len;
unsigned int data_len;
+ unsigned int extra_len; /* length of padding and draining buffers */
unsigned int sense_len;
void *data;
void *sense;
@@ -477,6 +477,12 @@ enum {
#define rq_data_dir(rq) ((rq)->cmd_flags & 1)
+/* data_len of the request sans extra stuff for padding and draining */
+static inline unsigned int blk_rq_raw_data_len(struct request *rq)
+{
+ return rq->data_len - min(rq->extra_len, rq->data_len);
+}
+
/*
* We regard a request as sync, if it's a READ or a SYNC write.
*/
Index: work/block/blk-settings.c
===================================================================
--- work.orig/block/blk-settings.c
+++ work/block/blk-settings.c
@@ -309,6 +309,10 @@ EXPORT_SYMBOL(blk_queue_stack_limits);
* does is adjust the queue so that the buf is always appended
* silently to the scatterlist.
*
+ * Appending draining buffer to a request modifies ->data_len such
+ * that it includes the drain buffer. The original requested data
+ * length can be obtained using blk_rq_raw_data_len().
+ *
* Note: This routine adjusts max_hw_segments to make room for
* appending the drain buffer. If you call
* blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
--
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