In the packet writing driver, if the drive reports a packet size
larger than the driver can handle, bail out safely instead of
triggering a BUG_ON.
Signed-off-by: Peter Osterlund <[email protected]>
---
drivers/block/pktcdvd.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -946,7 +946,6 @@ try_next_bio:
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 +1635,10 @@ static int pkt_probe_settings(struct pkt
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);
--
Peter Osterlund - [email protected]
http://web.telia.com/~u89404340
Update the "theory of operation" description.
Signed-off-by: Peter Osterlund <[email protected]>
---
drivers/block/pktcdvd.c | 48 +++++++++++++++++++++++++++++------------------
1 files changed, 30 insertions(+), 18 deletions(-)
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
--- 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.
*
*************************************************************************/
--
Peter Osterlund - [email protected]
http://web.telia.com/~u89404340
In the /proc statistics, only count writes that upper layers have
requested. Don't count additional writes created inside the packet
driver to satisfy the requirement to only write full packets.
Signed-off-by: Peter Osterlund <[email protected]>
---
drivers/block/pktcdvd.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -736,12 +736,6 @@ static void pkt_gather_data(struct pktcd
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.
*/
@@ -750,6 +744,7 @@ static void pkt_gather_data(struct pktcd
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++)
@@ -757,6 +752,12 @@ static void pkt_gather_data(struct pktcd
}
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.
*/
@@ -790,7 +791,6 @@ 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;
}
/*
--
Peter Osterlund - [email protected]
http://web.telia.com/~u89404340
Use kcalloc and kzalloc in pktcdvd.
Signed-off-by: Peter Osterlund <[email protected]>
---
drivers/block/pktcdvd.c | 9 +++------
1 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -112,10 +112,9 @@ static struct bio *pkt_bio_alloc(int nr_
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;
@@ -137,10 +136,9 @@ static struct packet_data *pkt_alloc_pac
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)
@@ -2492,10 +2490,9 @@ static int pkt_setup_dev(struct pkt_ctrl
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)
--
Peter Osterlund - [email protected]
http://web.telia.com/~u89404340
Remove some redundant BUG_ON() statements in pktcdvd and move one
run-time check to compile-time.
Signed-off-by: Peter Osterlund <[email protected]>
---
drivers/block/pktcdvd.c | 9 +++------
include/linux/pktcdvd.h | 3 +++
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -669,7 +669,6 @@ static void pkt_make_local_copy(struct p
}
offs += CD_FRAMESIZE;
if (offs >= PAGE_SIZE) {
- BUG_ON(offs > PAGE_SIZE);
offs = 0;
p++;
}
@@ -804,10 +803,11 @@ static struct packet_data *pkt_get_packe
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)
@@ -951,7 +951,6 @@ try_next_bio:
}
pkt = pkt_get_packet_data(pd, zone);
- BUG_ON(!pkt);
pd->current_sector = zone + pd->settings.size;
pkt->sector = zone;
@@ -2211,7 +2210,6 @@ static int pkt_make_request(request_queu
* 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);
@@ -2419,7 +2417,6 @@ static int pkt_ioctl(struct inode *inode
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) {
/*
diff --git a/include/linux/pktcdvd.h b/include/linux/pktcdvd.h
--- a/include/linux/pktcdvd.h
+++ b/include/linux/pktcdvd.h
@@ -166,6 +166,9 @@ struct packet_iosched
/*
* 32 buffers of 2048 bytes
*/
+#if (PAGE_SIZE % CD_FRAMESIZE) != 0
+#error "PAGE_SIZE must be a multiple of CD_FRAMESIZE"
+#endif
#define PACKET_MAX_SIZE 32
#define PAGES_PER_PACKET (PACKET_MAX_SIZE * CD_FRAMESIZE / PAGE_SIZE)
#define PACKET_MAX_SECTORS (PACKET_MAX_SIZE * CD_FRAMESIZE >> 9)
--
Peter Osterlund - [email protected]
http://web.telia.com/~u89404340