diff options
Diffstat (limited to 'drivers/block/pktcdvd.c')
| -rw-r--r-- | drivers/block/pktcdvd.c | 85 |
1 files changed, 47 insertions, 38 deletions
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c index 7b838342f0a3..7e22a58926b8 100644 --- a/drivers/block/pktcdvd.c +++ b/drivers/block/pktcdvd.c @@ -5,29 +5,41 @@ * May be copied or modified under the terms of the GNU General Public * License. See linux/COPYING for more information. * - * Packet writing layer for ATAPI and SCSI CD-R, CD-RW, DVD-R, and - * DVD-RW devices (aka an exercise in block layer masturbation) + * Packet writing layer for ATAPI and SCSI CD-RW, DVD+RW, DVD-RW and + * DVD-RAM devices. * + * Theory of operation: * - * TODO: (circa order of when I will fix it) - * - Only able to write on CD-RW media right now. - * - check host application code on media and set it in write page - * - interface for UDF <-> packet to negotiate a new location when a write - * fails. - * - handle OPC, especially for -RW media + * At the lowest level, there is the standard driver for the CD/DVD device, + * typically ide-cd.c or sr.c. This driver can handle read and write requests, + * but it doesn't know anything about the special restrictions that apply to + * packet writing. One restriction is that write requests must be aligned to + * packet boundaries on the physical media, and the size of a write request + * must be equal to the packet size. Another restriction is that a + * GPCMD_FLUSH_CACHE command has to be issued to the drive before a read + * command, if the previous command was a write. * - * Theory of operation: + * The purpose of the packet writing driver is to hide these restrictions from + * higher layers, such as file systems, and present a block device that can be + * randomly read and written using 2kB-sized blocks. + * + * The lowest layer in the packet writing driver is the packet I/O scheduler. + * Its data is defined by the struct packet_iosched and includes two bio + * queues with pending read and write requests. These queues are processed + * by the pkt_iosched_process_queue() function. The write requests in this + * queue are already properly aligned and sized. This layer is responsible for + * issuing the flush cache commands and scheduling the I/O in a good order. * - * We use a custom make_request_fn function that forwards reads directly to - * the underlying CD device. Write requests are either attached directly to - * a live packet_data object, or simply stored sequentially in a list for - * later processing by the kcdrwd kernel thread. This driver doesn't use - * any elevator functionally as defined by the elevator_s struct, but the - * underlying CD device uses a standard elevator. + * The next layer transforms unaligned write requests to aligned writes. This + * transformation requires reading missing pieces of data from the underlying + * block device, assembling the pieces to full packets and queuing them to the + * packet I/O scheduler. * - * This strategy makes it possible to do very late merging of IO requests. - * A new bio sent to pkt_make_request can be merged with a live packet_data - * object even if the object is in the data gathering state. + * At the top layer there is a custom make_request_fn function that forwards + * read requests directly to the iosched queue and puts write requests in the + * unaligned write queue. A kernel thread performs the necessary read + * gathering to convert the unaligned writes to aligned writes and then feeds + * them to the packet I/O scheduler. * *************************************************************************/ @@ -100,10 +112,9 @@ static struct bio *pkt_bio_alloc(int nr_iovecs) goto no_bio; bio_init(bio); - bvl = kmalloc(nr_iovecs * sizeof(struct bio_vec), GFP_KERNEL); + bvl = kcalloc(nr_iovecs, sizeof(struct bio_vec), GFP_KERNEL); if (!bvl) goto no_bvl; - memset(bvl, 0, nr_iovecs * sizeof(struct bio_vec)); bio->bi_max_vecs = nr_iovecs; bio->bi_io_vec = bvl; @@ -125,10 +136,9 @@ static struct packet_data *pkt_alloc_packet_data(void) int i; struct packet_data *pkt; - pkt = kmalloc(sizeof(struct packet_data), GFP_KERNEL); + pkt = kzalloc(sizeof(struct packet_data), GFP_KERNEL); if (!pkt) goto no_pkt; - memset(pkt, 0, sizeof(struct packet_data)); pkt->w_bio = pkt_bio_alloc(PACKET_MAX_SIZE); if (!pkt->w_bio) @@ -659,7 +669,6 @@ static void pkt_make_local_copy(struct packet_data *pkt, struct page **pages, in } offs += CD_FRAMESIZE; if (offs >= PAGE_SIZE) { - BUG_ON(offs > PAGE_SIZE); offs = 0; p++; } @@ -724,12 +733,6 @@ static void pkt_gather_data(struct pktcdvd_device *pd, struct packet_data *pkt) atomic_set(&pkt->io_wait, 0); atomic_set(&pkt->io_errors, 0); - if (pkt->cache_valid) { - VPRINTK("pkt_gather_data: zone %llx cached\n", - (unsigned long long)pkt->sector); - goto out_account; - } - /* * Figure out which frames we need to read before we can write. */ @@ -738,6 +741,7 @@ static void pkt_gather_data(struct pktcdvd_device *pd, struct packet_data *pkt) for (bio = pkt->orig_bios; bio; bio = bio->bi_next) { int first_frame = (bio->bi_sector - pkt->sector) / (CD_FRAMESIZE >> 9); int num_frames = bio->bi_size / CD_FRAMESIZE; + pd->stats.secs_w += num_frames * (CD_FRAMESIZE >> 9); BUG_ON(first_frame < 0); BUG_ON(first_frame + num_frames > pkt->frames); for (f = first_frame; f < first_frame + num_frames; f++) @@ -745,6 +749,12 @@ static void pkt_gather_data(struct pktcdvd_device *pd, struct packet_data *pkt) } spin_unlock(&pkt->lock); + if (pkt->cache_valid) { + VPRINTK("pkt_gather_data: zone %llx cached\n", + (unsigned long long)pkt->sector); + goto out_account; + } + /* * Schedule reads for missing parts of the packet. */ @@ -778,7 +788,6 @@ out_account: frames_read, (unsigned long long)pkt->sector); pd->stats.pkt_started++; pd->stats.secs_rg += frames_read * (CD_FRAMESIZE >> 9); - pd->stats.secs_w += pd->settings.size; } /* @@ -794,10 +803,11 @@ static struct packet_data *pkt_get_packet_data(struct pktcdvd_device *pd, int zo list_del_init(&pkt->list); if (pkt->sector != zone) pkt->cache_valid = 0; - break; + return pkt; } } - return pkt; + BUG(); + return NULL; } static void pkt_put_packet_data(struct pktcdvd_device *pd, struct packet_data *pkt) @@ -941,12 +951,10 @@ try_next_bio: } pkt = pkt_get_packet_data(pd, zone); - BUG_ON(!pkt); pd->current_sector = zone + pd->settings.size; pkt->sector = zone; pkt->frames = pd->settings.size >> 2; - BUG_ON(pkt->frames > PACKET_MAX_SIZE); pkt->write_size = 0; /* @@ -1636,6 +1644,10 @@ static int pkt_probe_settings(struct pktcdvd_device *pd) printk("pktcdvd: detected zero packet size!\n"); pd->settings.size = 128; } + if (pd->settings.size > PACKET_MAX_SECTORS) { + printk("pktcdvd: packet size is too big\n"); + return -ENXIO; + } pd->settings.fp = ti.fp; pd->offset = (be32_to_cpu(ti.track_start) << 2) & (pd->settings.size - 1); @@ -2198,7 +2210,6 @@ static int pkt_make_request(request_queue_t *q, struct bio *bio) * No matching packet found. Store the bio in the work queue. */ node = mempool_alloc(pd->rb_pool, GFP_NOIO); - BUG_ON(!node); node->bio = bio; spin_lock(&pd->lock); BUG_ON(pd->bio_queue_size < 0); @@ -2406,7 +2417,6 @@ static int pkt_ioctl(struct inode *inode, struct file *file, unsigned int cmd, u struct pktcdvd_device *pd = inode->i_bdev->bd_disk->private_data; VPRINTK("pkt_ioctl: cmd %x, dev %d:%d\n", cmd, imajor(inode), iminor(inode)); - BUG_ON(!pd); switch (cmd) { /* @@ -2477,10 +2487,9 @@ static int pkt_setup_dev(struct pkt_ctrl_command *ctrl_cmd) return -EBUSY; } - pd = kmalloc(sizeof(struct pktcdvd_device), GFP_KERNEL); + pd = kzalloc(sizeof(struct pktcdvd_device), GFP_KERNEL); if (!pd) return ret; - memset(pd, 0, sizeof(struct pktcdvd_device)); pd->rb_pool = mempool_create(PKT_RB_POOL_SIZE, pkt_rb_alloc, pkt_rb_free, NULL); if (!pd->rb_pool) |