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Subject[PATCH] bio traversal 1/2 - core changes

# Bio traversal (separate submittion/completion bio pointers).
# Patch 1/2 - Core changes.
#
# Originally by Suparna Bhattacharya.
#
# Bartlomiej Zolnierkiewicz <bzolnier@elka.pw.edu.pl>

diff -uNr linux-2.5.66/drivers/block/elevator.c linux/drivers/block/elevator.c
--- linux-2.5.66/drivers/block/elevator.c Fri Mar 21 14:23:25 2003
+++ linux/drivers/block/elevator.c Sat Mar 22 22:50:06 2003
@@ -324,6 +324,19 @@
if (&rq->queuelist == q->last_merge)
q->last_merge = NULL;

+ /*
+ * preset some fields (e.g. the req might have been restarted)
+ */
+ if ((rq->bio = rq->hard_bio)) {
+ rq->nr_bio_segments = bio_segments(rq->bio);
+ rq->nr_bio_sectors = bio_sectors(rq->bio);
+ rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
+ rq->buffer = bio_data(rq->bio);
+ }
+ rq->sector = rq->hard_sector;
+ rq->nr_sectors = rq->hard_nr_sectors;
+ rq->current_nr_sectors = rq->hard_cur_sectors;
+
if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
break;

diff -uNr linux-2.5.66/drivers/block/ll_rw_blk.c linux/drivers/block/ll_rw_blk.c
--- linux-2.5.66/drivers/block/ll_rw_blk.c Tue Mar 25 22:53:09 2003
+++ linux/drivers/block/ll_rw_blk.c Tue Mar 25 23:51:01 2003
@@ -1680,7 +1680,8 @@

sector = bio->bi_sector;
nr_sectors = bio_sectors(bio);
- cur_nr_sectors = bio_iovec(bio)->bv_len >> 9;
+ cur_nr_sectors = bio_cur_sectors(bio);
+
rw = bio_data_dir(bio);

/*
@@ -1736,7 +1737,10 @@
}

bio->bi_next = req->bio;
- req->bio = bio;
+ req->hard_bio = req->bio = bio;
+ req->nr_bio_segments = bio_segments(req->bio);
+ req->nr_bio_sectors = bio_sectors(req->bio);
+
/*
* may not be valid. if the low level driver said
* it didn't need a bounce buffer then it better
@@ -1806,7 +1810,9 @@
req->nr_hw_segments = bio_hw_segments(q, bio);
req->buffer = bio_data(bio); /* see ->buffer comment above */
req->waiting = NULL;
- req->bio = req->biotail = bio;
+ req->hard_bio = req->bio = req->biotail = bio;
+ req->nr_bio_segments = bio_segments(req->bio);
+ req->nr_bio_sectors = bio_sectors(req->bio);
req->rq_disk = bio->bi_bdev->bd_disk;
req->start_time = jiffies;
add_request(q, req, insert_here);
@@ -1985,10 +1991,8 @@
if (!rq->bio)
return;

- rq->buffer = bio_data(rq->bio);
-
nr_phys_segs = nr_hw_segs = 0;
- rq_for_each_bio(bio, rq) {
+ rq_for_each_hard_bio(bio, rq) {
/* Force bio hw/phys segs to be recalculated. */
bio->bi_flags &= ~(1 << BIO_SEG_VALID);

@@ -2004,11 +2008,24 @@
{
if (blk_fs_request(rq)) {
rq->hard_sector += nsect;
- rq->nr_sectors = rq->hard_nr_sectors -= nsect;
- rq->sector = rq->hard_sector;
+ rq->hard_nr_sectors -= nsect;

- rq->current_nr_sectors = bio_iovec(rq->bio)->bv_len >> 9;
- rq->hard_cur_sectors = rq->current_nr_sectors;
+ /*
+ * Move the I/O submission pointers ahead if required
+ * (i.e. if the driver doesn't update them).
+ */
+ if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
+ (rq->sector <= rq->hard_sector)) {
+ rq->sector = rq->hard_sector;
+ rq->nr_sectors = rq->hard_nr_sectors;
+ rq->bio = rq->hard_bio;
+ rq->nr_bio_segments = bio_segments(rq->bio);
+ rq->nr_bio_sectors = bio_sectors(rq->bio);
+ rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
+ rq->current_nr_sectors = rq->hard_cur_sectors;
+
+ rq->buffer = bio_data(rq->bio);
+ }

/*
* if total number of sectors is less than the first segment
@@ -2043,11 +2060,11 @@
}

total_bytes = bio_nbytes = 0;
- while ((bio = req->bio)) {
+ while ((bio = req->hard_bio)) {
int nbytes;

if (nr_bytes >= bio->bi_size) {
- req->bio = bio->bi_next;
+ req->hard_bio = bio->bi_next;
nbytes = bio->bi_size;
bio_endio(bio, nbytes, error);
next_idx = 0;
@@ -2087,7 +2104,7 @@
total_bytes += nbytes;
nr_bytes -= nbytes;

- if ((bio = req->bio)) {
+ if ((bio = req->hard_bio)) {
/*
* end more in this run, or just return 'not-done'
*/
@@ -2099,7 +2116,7 @@
/*
* completely done
*/
- if (!req->bio)
+ if (!req->hard_bio)
return 0;

/*
@@ -2107,7 +2124,7 @@
*/
if (bio_nbytes) {
bio_endio(bio, bio_nbytes, error);
- req->bio->bi_idx += next_idx;
+ req->hard_bio->bi_idx += next_idx;
}

blk_recalc_rq_sectors(req, total_bytes >> 9);
@@ -2181,6 +2198,80 @@
__blk_put_request(req->q, req);
}

+/**
+ * blk_rq_next_segment
+ * @rq: the request being processed
+ *
+ * Description:
+ * Points to the next segment in the request if the current segment
+ * is complete. Leaves things unchanged if this segment is not over
+ * or if no more segments are left in this request.
+ *
+ * Meant to be used for bio traversal during I/O submission
+ * Does not effect any I/O completions or update completion state
+ * in the request, and does not modify any bio fields.
+ *
+ * Decrementing rq->nr_sectors, rq->current_nr_sectors and
+ * rq->nr_bio_sectors as data is transferred is the caller's
+ * responsibility and should be done before calling this routine.
+ **/
+void blk_rq_next_segment(struct request *rq)
+{
+ if (rq->current_nr_sectors > 0)
+ return;
+
+ if (rq->nr_bio_sectors > 0) {
+ --rq->nr_bio_segments;
+ rq->current_nr_sectors = blk_rq_vec(rq)->bv_len >> 9;
+ } else {
+ if ((rq->bio = rq->bio->bi_next)) {
+ rq->nr_bio_segments = bio_segments(rq->bio);
+ rq->nr_bio_sectors = bio_sectors(rq->bio);
+ rq->current_nr_sectors = bio_cur_sectors(rq->bio);
+ }
+ }
+
+ /* remember the size of this segment before we start I/O */
+ rq->hard_cur_sectors = rq->current_nr_sectors;
+}
+
+/**
+ * process_that_request_first - process partial request submission
+ * @req: the request being processed
+ * @nr_sectors: number of sectors I/O has been submitted on
+ *
+ * Description:
+ * May be used for processing bio's while submitting I/O without
+ * signalling completion. Fails if more data is requested than is
+ * available in the request in which case it doesn't advance any
+ * pointers.
+ *
+ * Assumes a request is correctly set up. No sanity checks.
+ *
+ * Return:
+ * 0 - no more data left to submit (not processed)
+ * 1 - data available to submit for this request (processed)
+ **/
+int process_that_request_first(struct request *req, unsigned int nr_sectors)
+{
+ unsigned int nsect;
+
+ if (req->nr_sectors < nr_sectors)
+ return 0;
+
+ req->nr_sectors -= nr_sectors;
+ req->sector += nr_sectors;
+ while (nr_sectors) {
+ nsect = min_t(unsigned int, req->current_nr_sectors,
+ nr_sectors);
+ req->current_nr_sectors -= nsect;
+ req->nr_bio_sectors -= nsect;
+ nr_sectors -= nsect;
+ blk_rq_next_segment(req);
+ }
+ return 1;
+}
+
int __init blk_dev_init(void)
{
int total_ram = nr_free_pages() << (PAGE_SHIFT - 10);
@@ -2223,6 +2314,7 @@
EXPORT_SYMBOL(end_that_request_first);
EXPORT_SYMBOL(end_that_request_chunk);
EXPORT_SYMBOL(end_that_request_last);
+EXPORT_SYMBOL(process_that_request_first);
EXPORT_SYMBOL(blk_init_queue);
EXPORT_SYMBOL(blk_cleanup_queue);
EXPORT_SYMBOL(blk_queue_make_request);
diff -uNr linux-2.5.66/include/linux/bio.h linux/include/linux/bio.h
--- linux-2.5.66/include/linux/bio.h Fri Mar 21 14:24:36 2003
+++ linux/include/linux/bio.h Sat Mar 22 22:52:16 2003
@@ -131,6 +131,7 @@
#define bio_iovec(bio) bio_iovec_idx((bio), (bio)->bi_idx)
#define bio_page(bio) bio_iovec((bio))->bv_page
#define bio_offset(bio) bio_iovec((bio))->bv_offset
+#define bio_segments(bio) ((bio)->bi_vcnt - (bio)->bi_idx)
#define bio_sectors(bio) ((bio)->bi_size >> 9)
#define bio_cur_sectors(bio) (bio_iovec(bio)->bv_len >> 9)
#define bio_data(bio) (page_address(bio_page((bio))) + bio_offset((bio)))
@@ -225,12 +226,15 @@
#ifdef CONFIG_HIGHMEM
/*
* remember to add offset! and never ever reenable interrupts between a
- * bio_kmap_irq and bio_kunmap_irq!!
+ * bvec_kmap_irq and bvec_kunmap_irq!!
*
* This function MUST be inlined - it plays with the CPU interrupt flags.
* Hence the `extern inline'.
+ *
+ * We use bio_vec * directly here instead of bio_page(bio) because we also
+ * want to use this function for bio_vec's different than bio->bi_idx one.
*/
-extern inline char *bio_kmap_irq(struct bio *bio, unsigned long *flags)
+extern inline char *bvec_kmap_irq(struct bio_vec *bvec, unsigned long *flags)
{
unsigned long addr;

@@ -239,15 +243,15 @@
* balancing is a lot nicer this way
*/
local_save_flags(*flags);
- addr = (unsigned long) kmap_atomic(bio_page(bio), KM_BIO_SRC_IRQ);
+ addr = (unsigned long) kmap_atomic(bvec->bv_page, KM_BIO_SRC_IRQ);

if (addr & ~PAGE_MASK)
BUG();

- return (char *) addr + bio_offset(bio);
+ return (char *) addr + bvec->bv_offset;
}

-extern inline void bio_kunmap_irq(char *buffer, unsigned long *flags)
+extern inline void bvec_kunmap_irq(char *buffer, unsigned long *flags)
{
unsigned long ptr = (unsigned long) buffer & PAGE_MASK;

@@ -256,8 +260,20 @@
}

#else
-#define bio_kmap_irq(bio, flags) (bio_data(bio))
-#define bio_kunmap_irq(buf, flags) do { *(flags) = 0; } while (0)
+#define bvec_kmap_irq(bvec, flags) (page_address((bvec)->bv_page) + (bvec)->bv_offset)
+#define bvec_kunmap_irq(buf, flags) do { *(flags) = 0; } while (0)
#endif

+extern inline char *__bio_kmap_irq(struct bio *bio, unsigned short idx,
+ unsigned long *flags)
+{
+ return bvec_kmap_irq(bio_iovec_idx(bio, idx), flags);
+}
+#define __bio_kunmap_irq bvec_kunmap_irq
+
+/* Will be removed soon. */
+#define bio_kmap_irq(bio, flags) \
+ __bio_kmap_irq((bio), (bio)->bi_idx, (flags))
+#define bio_kunmap_irq __bio_kunmap_irq
+
#endif /* __LINUX_BIO_H */
diff -uNr linux-2.5.66/include/linux/blk.h linux/include/linux/blk.h
--- linux-2.5.66/include/linux/blk.h Fri Mar 21 14:23:25 2003
+++ linux/include/linux/blk.h Sat Mar 22 22:50:06 2003
@@ -43,6 +43,7 @@
extern int end_that_request_first(struct request *, int, int);
extern int end_that_request_chunk(struct request *, int, int);
extern void end_that_request_last(struct request *);
+extern int process_that_request_first(struct request *, unsigned int);
struct request *elv_next_request(request_queue_t *q);

static inline void blkdev_dequeue_request(struct request *req)
diff -uNr linux-2.5.66/include/linux/blkdev.h linux/include/linux/blkdev.h
--- linux-2.5.66/include/linux/blkdev.h Fri Mar 21 14:23:25 2003
+++ linux/include/linux/blkdev.h Sat Mar 22 22:50:06 2003
@@ -10,6 +10,7 @@
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/wait.h>
+#include <linux/bio.h>

#include <asm/scatterlist.h>

@@ -33,9 +34,28 @@
* blkdev_dequeue_request! */
unsigned long flags; /* see REQ_ bits below */

- sector_t sector;
- unsigned long nr_sectors;
+ /* Maintain bio traversal state for part by part I/O submission.
+ * hard_* are block layer internals, no driver should touch them!
+ */
+
+ sector_t sector; /* next sector to submit */
+ unsigned long nr_sectors; /* no. of sectors left to submit */
+
+ sector_t hard_sector; /* next sector to complete */
+ unsigned long hard_nr_sectors; /* no. of sectors left to complete */
+
+ /* no. of segments left to submit in the current bio */
+ unsigned short nr_bio_segments;
+ /* no. of sectors left to submit in the current bio */
+ unsigned long nr_bio_sectors;
+ /* no. of sectors left to submit in the current segment */
unsigned int current_nr_sectors;
+ /* no. of sectors left to complete in the current segment */
+ unsigned int hard_cur_sectors;
+
+ struct bio *bio; /* next bio to submit */
+ struct bio *hard_bio; /* next unfinished bio to complete */
+ struct bio *biotail;

void *elevator_private;

@@ -43,15 +63,6 @@
struct gendisk *rq_disk;
int errors;
unsigned long start_time;
- sector_t hard_sector; /* the hard_* are block layer
- * internals, no driver should
- * touch them
- */
- unsigned long hard_nr_sectors;
- unsigned int hard_cur_sectors;
-
- struct bio *bio;
- struct bio *biotail;

/* Number of scatter-gather DMA addr+len pairs after
* physical address coalescing is performed.
@@ -282,6 +293,32 @@
*/
#define blk_queue_headactive(q, head_active)

+/* current index into bio being processed for submission */
+#define blk_rq_idx(rq) ((rq)->bio->bi_vcnt - (rq)->nr_bio_segments)
+
+/* current bio vector being processed */
+#define blk_rq_vec(rq) (bio_iovec_idx((rq)->bio, blk_rq_idx(rq)))
+
+/*
+ * temporarily mapping a (possible) highmem bio (typically for PIO transfer)
+ */
+
+/* current offset with respect to start of the segment being submitted */
+#define blk_rq_offset(rq) \
+ (((rq)->hard_cur_sectors - (rq)->current_nr_sectors) << 9)
+
+/* Assumes rq->bio != NULL */
+static inline char * rq_map_buffer(struct request *rq, unsigned long *flags)
+{
+ return (__bio_kmap_irq(rq->bio, blk_rq_idx(rq), flags)
+ + blk_rq_offset(rq));
+}
+
+static inline void rq_unmap_buffer(char *buffer, unsigned long *flags)
+{
+ __bio_kunmap_irq(buffer, flags);
+}
+
/*
* q->prep_rq_fn return values
*/
@@ -319,6 +356,10 @@
if ((rq->bio)) \
for (bio = (rq)->bio; bio; bio = bio->bi_next)

+#define rq_for_each_hard_bio(bio, rq) \
+ if ((rq->hard_bio)) \
+ for (bio = (rq)->hard_bio; bio; bio = bio->bi_next)
+
struct sec_size {
unsigned block_size;
unsigned block_size_bits;
diff -uNr linux-2.5.66/mm/highmem.c linux/mm/highmem.c
--- linux-2.5.66/mm/highmem.c Tue Mar 25 22:53:11 2003
+++ linux/mm/highmem.c Tue Mar 25 23:51:01 2003
@@ -431,7 +431,7 @@
bio->bi_rw = (*bio_orig)->bi_rw;

bio->bi_vcnt = (*bio_orig)->bi_vcnt;
- bio->bi_idx = 0;
+ bio->bi_idx = (*bio_orig)->bi_idx;
bio->bi_size = (*bio_orig)->bi_size;

if (pool == page_pool) {

-
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