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ide-cd: remove the internal 64k buffer
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This removes the internal ide-cd buffer and falls back to read-ahead block layer
capabilities. Thorough testing (cd burning, dvd read, raw read) gives with the
bufferless mode marginally better performance in addition to simplified code.

bufferless:

dd: reading `/dev/hdc': Input/output error
6238+0 records in
6238+0 records out
204406784 bytes (204 MB) copied, 259.891 s, 787 kB/s

real    4m21.598s
user    0m0.014s
sys     0m0.744s

with the old buffer (2.6.25-rc1):

dd: reading `/dev/hdc': Input/output error
6238+0 records in
6238+0 records out
204406784 bytes (204 MB) copied, 262.893 s, 778 kB/s

real    4m22.938s
user    0m0.009s
sys     0m0.771s

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
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Borislav Petkov authored and Bartlomiej Zolnierkiewicz committed Apr 26, 2008
1 parent 9841654 commit 968c496
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Showing 2 changed files with 4 additions and 123 deletions.
123 changes: 4 additions & 119 deletions drivers/ide/ide-cd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,7 +89,6 @@ static void cdrom_saw_media_change (ide_drive_t *drive)

cd->cd_flags |= IDE_CD_FLAG_MEDIA_CHANGED;
cd->cd_flags &= ~IDE_CD_FLAG_TOC_VALID;
cd->nsectors_buffered = 0;
}

static int cdrom_log_sense(ide_drive_t *drive, struct request *rq,
Expand Down Expand Up @@ -625,47 +624,6 @@ static void ide_cd_drain_data(ide_drive_t *drive, int nsects)
}
}

/*
* Buffer up to SECTORS_TO_TRANSFER sectors from the drive in our sector
* buffer. Once the first sector is added, any subsequent sectors are
* assumed to be continuous (until the buffer is cleared). For the first
* sector added, SECTOR is its sector number. (SECTOR is then ignored until
* the buffer is cleared.)
*/
static void cdrom_buffer_sectors (ide_drive_t *drive, unsigned long sector,
int sectors_to_transfer)
{
struct cdrom_info *info = drive->driver_data;

/* Number of sectors to read into the buffer. */
int sectors_to_buffer = min_t(int, sectors_to_transfer,
(SECTOR_BUFFER_SIZE >> SECTOR_BITS) -
info->nsectors_buffered);

char *dest;

/* If we couldn't get a buffer, don't try to buffer anything... */
if (info->buffer == NULL)
sectors_to_buffer = 0;

/* If this is the first sector in the buffer, remember its number. */
if (info->nsectors_buffered == 0)
info->sector_buffered = sector;

/* Read the data into the buffer. */
dest = info->buffer + info->nsectors_buffered * SECTOR_SIZE;
while (sectors_to_buffer > 0) {
HWIF(drive)->atapi_input_bytes(drive, dest, SECTOR_SIZE);
--sectors_to_buffer;
--sectors_to_transfer;
++info->nsectors_buffered;
dest += SECTOR_SIZE;
}

/* Throw away any remaining data. */
ide_cd_drain_data(drive, sectors_to_transfer);
}

/*
* Check the contents of the interrupt reason register from the cdrom
* and attempt to recover if there are problems. Returns 0 if everything's
Expand Down Expand Up @@ -734,65 +692,6 @@ static int ide_cd_check_transfer_size(ide_drive_t *drive, int len)
return 1;
}

/*
* Try to satisfy some of the current read request from our cached data.
* Returns nonzero if the request has been completed, zero otherwise.
*/
static int cdrom_read_from_buffer (ide_drive_t *drive)
{
struct cdrom_info *info = drive->driver_data;
struct request *rq = HWGROUP(drive)->rq;
unsigned short sectors_per_frame;

sectors_per_frame = queue_hardsect_size(drive->queue) >> SECTOR_BITS;

/* Can't do anything if there's no buffer. */
if (info->buffer == NULL) return 0;

/* Loop while this request needs data and the next block is present
in our cache. */
while (rq->nr_sectors > 0 &&
rq->sector >= info->sector_buffered &&
rq->sector < info->sector_buffered + info->nsectors_buffered) {
if (rq->current_nr_sectors == 0)
cdrom_end_request(drive, 1);

memcpy (rq->buffer,
info->buffer +
(rq->sector - info->sector_buffered) * SECTOR_SIZE,
SECTOR_SIZE);
rq->buffer += SECTOR_SIZE;
--rq->current_nr_sectors;
--rq->nr_sectors;
++rq->sector;
}

/* If we've satisfied the current request,
terminate it successfully. */
if (rq->nr_sectors == 0) {
cdrom_end_request(drive, 1);
return -1;
}

/* Move on to the next buffer if needed. */
if (rq->current_nr_sectors == 0)
cdrom_end_request(drive, 1);

/* If this condition does not hold, then the kluge i use to
represent the number of sectors to skip at the start of a transfer
will fail. I think that this will never happen, but let's be
paranoid and check. */
if (rq->current_nr_sectors < bio_cur_sectors(rq->bio) &&
(rq->sector & (sectors_per_frame - 1))) {
printk(KERN_ERR "%s: cdrom_read_from_buffer: buffer botch (%ld)\n",
drive->name, (long)rq->sector);
cdrom_end_request(drive, 0);
return -1;
}

return 0;
}

static ide_startstop_t cdrom_newpc_intr(ide_drive_t *);

/*
Expand Down Expand Up @@ -1134,11 +1033,9 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
if (!ptr) {
if (blk_fs_request(rq) && !write)
/*
* If the buffers are full, cache the rest
* of the data in our internal buffer.
*/
cdrom_buffer_sectors(drive, rq->sector,
thislen >> 9);
* If the buffers are full, pipe the rest into
* oblivion. */
ide_cd_drain_data(drive, thislen >> 9);
else {
printk(KERN_ERR "%s: confused, missing data\n",
drive->name);
Expand Down Expand Up @@ -1243,10 +1140,6 @@ static ide_startstop_t cdrom_start_rw(ide_drive_t *drive, struct request *rq)
* weirdness which might be present in the request packet.
*/
restore_request(rq);

/* Satisfy whatever we can of this request from our cache. */
if (cdrom_read_from_buffer(drive))
return ide_stopped;
}

/*
Expand All @@ -1262,9 +1155,6 @@ static ide_startstop_t cdrom_start_rw(ide_drive_t *drive, struct request *rq)
} else
cd->dma = drive->using_dma;

/* Clear the local sector buffer. */
cd->nsectors_buffered = 0;

if (write)
cd->devinfo.media_written = 1;

Expand Down Expand Up @@ -2030,7 +1920,6 @@ static void ide_cd_release(struct kref *kref)
ide_drive_t *drive = info->drive;
struct gendisk *g = info->disk;

kfree(info->buffer);
kfree(info->toc);
if (devinfo->handle == drive)
unregister_cdrom(devinfo);
Expand Down Expand Up @@ -2090,11 +1979,7 @@ static int idecd_open(struct inode * inode, struct file * file)
if (!(info = ide_cd_get(disk)))
return -ENXIO;

if (!info->buffer)
info->buffer = kmalloc(SECTOR_BUFFER_SIZE, GFP_KERNEL|__GFP_REPEAT);

if (info->buffer)
rc = cdrom_open(&info->devinfo, inode, file);
rc = cdrom_open(&info->devinfo, inode, file);

if (rc < 0)
ide_cd_put(info);
Expand Down
4 changes: 0 additions & 4 deletions drivers/ide/ide-cd.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -119,10 +119,6 @@ struct cdrom_info {

struct atapi_toc *toc;

unsigned long sector_buffered;
unsigned long nsectors_buffered;
unsigned char *buffer;

/* The result of the last successful request sense command
on this device. */
struct request_sense sense_data;
Expand Down

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