/*- * SPDX-License-Identifier: Beerware * * ---------------------------------------------------------------------------- * "THE BEER-WARE LICENSE" (Revision 42): * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you * can do whatever you want with this stuff. If we meet some day, and you think * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp * ---------------------------------------------------------------------------- * * The bioq_disksort() (and the specification of the bioq API) * have been written by Luigi Rizzo and Fabio Checconi under the same * license as above. */ #include <sys/cdefs.h> #include "opt_geom.h" #include <sys/param.h> #include <sys/systm.h> #include <sys/bio.h> #include <sys/conf.h> #include <sys/disk.h> #include <sys/sysctl.h> #include <geom/geom_disk.h> static int bioq_batchsize = 128; SYSCTL_INT(_debug, OID_AUTO, bioq_batchsize, CTLFLAG_RW, &bioq_batchsize, 0, "BIOQ batch size"); /*- * Disk error is the preface to plaintive error messages * about failing disk transfers. It prints messages of the form * "hp0g: BLABLABLA cmd=read fsbn 12345 of 12344-12347" * blkdone should be -1 if the position of the error is unknown. * The message is printed with printf. */ void disk_err(struct bio *bp, const char *what, int blkdone, int nl) { daddr_t sn; if (bp->bio_dev != NULL) printf("%s: %s ", devtoname(bp->bio_dev), what); else if (bp->bio_disk != NULL) printf("%s%d: %s ", bp->bio_disk->d_name, bp->bio_disk->d_unit, what); else printf("disk??: %s ", what); switch(bp->bio_cmd) { case BIO_READ: printf("cmd=read "); break; case BIO_WRITE: printf("cmd=write "); break; case BIO_DELETE: printf("cmd=delete "); break; case BIO_GETATTR: printf("cmd=getattr "); break; case BIO_FLUSH: printf("cmd=flush "); break; default: printf("cmd=%x ", bp->bio_cmd); break; } sn = bp->bio_pblkno; if (bp->bio_bcount <= DEV_BSIZE) { printf("fsbn %jd%s", (intmax_t)sn, nl ? "\n" : ""); return; } if (blkdone >= 0) { sn += blkdone; printf("fsbn %jd of ", (intmax_t)sn); } printf("%jd-%jd", (intmax_t)bp->bio_pblkno, (intmax_t)(bp->bio_pblkno + (bp->bio_bcount - 1) / DEV_BSIZE)); if (nl) printf("\n"); } /* * BIO queue implementation * * Please read carefully the description below before making any change * to the code, or you might change the behaviour of the data structure * in undesirable ways. * * A bioq stores disk I/O request (bio), normally sorted according to * the distance of the requested position (bio->bio_offset) from the * current head position (bioq->last_offset) in the scan direction, i.e. * * (uoff_t)(bio_offset - last_offset) * * Note that the cast to unsigned (uoff_t) is fundamental to insure * that the distance is computed in the scan direction. * * The main methods for manipulating the bioq are: * * bioq_disksort() performs an ordered insertion; * * bioq_first() return the head of the queue, without removing; * * bioq_takefirst() return and remove the head of the queue, * updating the 'current head position' as * bioq->last_offset = bio->bio_offset + bio->bio_length; * * When updating the 'current head position', we assume that the result of * bioq_takefirst() is dispatched to the device, so bioq->last_offset * represents the head position once the request is complete. * * If the bioq is manipulated using only the above calls, it starts * with a sorted sequence of requests with bio_offset >= last_offset, * possibly followed by another sorted sequence of requests with * 0 <= bio_offset < bioq->last_offset * * NOTE: historical behaviour was to ignore bio->bio_length in the * update, but its use tracks the head position in a better way. * Historical behaviour was also to update the head position when * the request under service is complete, rather than when the * request is extracted from the queue. However, the current API * has no method to update the head position; secondly, once * a request has been submitted to the disk, we have no idea of * the actual head position, so the final one is our best guess. * * --- Direct queue manipulation --- * * A bioq uses an underlying TAILQ to store requests, so we also * export methods to manipulate the TAILQ, in particular: * * bioq_insert_tail() insert an entry at the end. * It also creates a 'barrier' so all subsequent * insertions through bioq_disksort() will end up * after this entry; * * bioq_insert_head() insert an entry at the head, update * bioq->last_offset = bio->bio_offset so that * all subsequent insertions through bioq_disksort() * will end up after this entry; * * bioq_remove() remove a generic element from the queue, act as * bioq_takefirst() if invoked on the head of the queue. * * The semantic of these methods is the same as the operations * on the underlying TAILQ, but with additional guarantees on * subsequent bioq_disksort() calls. E.g. bioq_insert_tail() * can be useful for making sure that all previous ops are flushed * to disk before continuing. * * Updating bioq->last_offset on a bioq_insert_head() guarantees * that the bio inserted with the last bioq_insert_head() will stay * at the head of the queue even after subsequent bioq_disksort(). * * Note that when the direct queue manipulation functions are used, * the queue may contain multiple inversion points (i.e. more than * two sorted sequences of requests). * */ void bioq_init(struct bio_queue_head *head) { TAILQ_INIT(&head->queue); head->last_offset = 0; head->insert_point = NULL; head->total = 0; head->batched = 0; } void bioq_remove(struct bio_queue_head *head, struct bio *bp) { if (head->insert_point == NULL) { if (bp == TAILQ_FIRST(&head->queue)) head->last_offset = bp->bio_offset + bp->bio_length; } else if (bp == head->insert_point) head->insert_point = NULL; TAILQ_REMOVE(&head->queue, bp, bio_queue); if (TAILQ_EMPTY(&head->queue)) head->batched = 0; head->total--; } void bioq_flush(struct bio_queue_head *head, struct devstat *stp, int error) { struct bio *bp; while ((bp = bioq_takefirst(head)) != NULL) biofinish(bp, stp, error); } void bioq_insert_head(struct bio_queue_head *head, struct bio *bp) { if (head->insert_point == NULL) head->last_offset = bp->bio_offset; TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue); head->total++; head->batched = 0; } void bioq_insert_tail(struct bio_queue_head *head, struct bio *bp) { TAILQ_INSERT_TAIL(&head->queue, bp, bio_queue); head->total++; head->batched = 0; head->insert_point = bp; head->last_offset = bp->bio_offset; } struct bio * bioq_first(struct bio_queue_head *head) { return (TAILQ_FIRST(&head->queue)); } struct bio * bioq_takefirst(struct bio_queue_head *head) { struct bio *bp; bp = TAILQ_FIRST(&head->queue); if (bp != NULL) bioq_remove(head, bp); return (bp); } /* * Compute the sorting key. The cast to unsigned is * fundamental for correctness, see the description * near the beginning of the file. */ static inline uoff_t bioq_bio_key(struct bio_queue_head *head, struct bio *bp) { return ((uoff_t)(bp->bio_offset - head->last_offset)); } /* * Seek sort for disks. * * Sort all requests in a single queue while keeping * track of the current position of the disk with last_offset. * See above for details. */ void bioq_disksort(struct bio_queue_head *head, struct bio *bp) { struct bio *cur, *prev; uoff_t key; if ((bp->bio_flags & BIO_ORDERED) != 0) { /* * Ordered transactions can only be dispatched * after any currently queued transactions. They * also have barrier semantics - no transactions * queued in the future can pass them. */ bioq_insert_tail(head, bp); return; } /* * We should only sort requests of types that have concept of offset. * Other types, such as BIO_FLUSH or BIO_ZONE, may imply some degree * of ordering even if strict ordering is not requested explicitly. */ if (bp->bio_cmd != BIO_READ && bp->bio_cmd != BIO_WRITE && bp->bio_cmd != BIO_DELETE) { bioq_insert_tail(head, bp); return; } if (bioq_batchsize > 0 && head->batched > bioq_batchsize) { bioq_insert_tail(head, bp); return; } prev = NULL; key = bioq_bio_key(head, bp); cur = TAILQ_FIRST(&head->queue); if (head->insert_point) { prev = head->insert_point; cur = TAILQ_NEXT(head->insert_point, bio_queue); } while (cur != NULL && key >= bioq_bio_key(head, cur)) { prev = cur; cur = TAILQ_NEXT(cur, bio_queue); } if (prev == NULL) TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue); else TAILQ_INSERT_AFTER(&head->queue, prev, bp, bio_queue); head->total++; head->batched++; }
