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Refactor dmu_req_copy for immutable biovec changes

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Originally, dmu_req_copy modifies bv_len and bv_offset in bio_vec so that it
can continue in subsequent passes. However, after the immutable biovec changes
in Linux 3.14, this is not allowed. So instead, we just tell dmu_req_copy how
many bytes are already copied and it will skip to the right spot accordingly.

Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2124
This commit is contained in:
Chunwei Chen 2014-03-29 19:49:55 +08:00 committed by Brian Behlendorf
parent d4541210f3
commit 215b4634c7
1 changed files with 39 additions and 28 deletions
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67
module/zfs/dmu.c
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@ -1004,48 +1004,53 @@ xuio_stat_wbuf_nocopy()
/*
* Copy up to size bytes between arg_buf and req based on the data direction
* described by the req. If an entire req's data cannot be transfered the
* req's is updated such that it's current index and bv offsets correctly
* reference any residual data which could not be copied. The return value
* is the number of bytes successfully copied to arg_buf.
* described by the req. If an entire req's data cannot be transfered in one
* pass, you should pass in @req_offset to indicate where to continue. The
* return value is the number of bytes successfully copied to arg_buf.
*/
static int
dmu_req_copy(void *arg_buf, int size, int *offset, struct request *req)
dmu_req_copy(void *arg_buf, int size, struct request *req, size_t req_offset)
{
struct bio_vec *bv;
struct req_iterator iter;
char *bv_buf;
int tocpy;
int tocpy, bv_len, bv_offset;
int offset = 0;
*offset = 0;
rq_for_each_segment(bv, req, iter) {
/*
* Fully consumed the passed arg_buf. We use goto here because
* rq_for_each_segment is a double loop
*/
ASSERT3S(offset, <=, size);
if (size == offset)
goto out;
/* Fully consumed the passed arg_buf */
ASSERT3S(*offset, <=, size);
if (size == *offset)
break;
/* Skip fully consumed bv's */
if (bv->bv_len == 0)
/* Skip already copied bv */
if (req_offset >= bv->bv_len) {
req_offset -= bv->bv_len;
continue;
}
tocpy = MIN(bv->bv_len, size - *offset);
bv_len = bv->bv_len - req_offset;
bv_offset = bv->bv_offset + req_offset;
req_offset = 0;
tocpy = MIN(bv_len, size - offset);
ASSERT3S(tocpy, >=, 0);
bv_buf = page_address(bv->bv_page) + bv->bv_offset;
bv_buf = page_address(bv->bv_page) + bv_offset;
ASSERT3P(bv_buf, !=, NULL);
if (rq_data_dir(req) == WRITE)
memcpy(arg_buf + *offset, bv_buf, tocpy);
memcpy(arg_buf + offset, bv_buf, tocpy);
else
memcpy(bv_buf, arg_buf + *offset, tocpy);
memcpy(bv_buf, arg_buf + offset, tocpy);
*offset += tocpy;
bv->bv_offset += tocpy;
bv->bv_len -= tocpy;
offset += tocpy;
}
return (0);
out:
return (offset);
}
static void
@ -1101,6 +1106,7 @@ dmu_read_req(objset_t *os, uint64_t object, struct request *req)
struct bio *bio_saved = req->bio;
dmu_buf_t **dbp;
int numbufs, i, err;
size_t req_offset;
/*
* NB: we could do this block-at-a-time, but it's nice
@ -1122,6 +1128,7 @@ dmu_read_req(objset_t *os, uint64_t object, struct request *req)
if (err)
goto error;
req_offset = 0;
for (i = 0; i < numbufs; i++) {
int tocpy, didcpy, bufoff;
dmu_buf_t *db = dbp[i];
@ -1133,7 +1140,8 @@ dmu_read_req(objset_t *os, uint64_t object, struct request *req)
if (tocpy == 0)
break;
err = dmu_req_copy(db->db_data + bufoff, tocpy, &didcpy, req);
didcpy = dmu_req_copy(db->db_data + bufoff, tocpy, req,
req_offset);
if (didcpy < tocpy)
err = EIO;
@ -1143,6 +1151,7 @@ dmu_read_req(objset_t *os, uint64_t object, struct request *req)
size -= tocpy;
offset += didcpy;
req_offset += didcpy;
err = 0;
}
@ -1161,9 +1170,8 @@ dmu_write_req(objset_t *os, uint64_t object, struct request *req, dmu_tx_t *tx)
uint64_t offset = blk_rq_pos(req) << 9;
struct bio *bio_saved = req->bio;
dmu_buf_t **dbp;
int numbufs;
int err = 0;
int i;
int numbufs, i, err;
size_t req_offset;
if (size == 0)
return (0);
@ -1184,6 +1192,7 @@ dmu_write_req(objset_t *os, uint64_t object, struct request *req, dmu_tx_t *tx)
if (err)
goto error;
req_offset = 0;
for (i = 0; i < numbufs; i++) {
int tocpy, didcpy, bufoff;
dmu_buf_t *db = dbp[i];
@ -1202,7 +1211,8 @@ dmu_write_req(objset_t *os, uint64_t object, struct request *req, dmu_tx_t *tx)
else
dmu_buf_will_dirty(db, tx);
err = dmu_req_copy(db->db_data + bufoff, tocpy, &didcpy, req);
didcpy = dmu_req_copy(db->db_data + bufoff, tocpy, req,
req_offset);
if (tocpy == db->db_size)
dmu_buf_fill_done(db, tx);
@ -1215,6 +1225,7 @@ dmu_write_req(objset_t *os, uint64_t object, struct request *req, dmu_tx_t *tx)
size -= tocpy;
offset += didcpy;
req_offset += didcpy;
err = 0;
}