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Commit 968c4964 authored by Borislav Petkov's avatar Borislav Petkov Committed by Bartlomiej Zolnierkiewicz
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ide-cd: remove the internal 64k buffer 



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: default avatarBorislav Petkov <petkovbb@gmail.com>
Signed-off-by: default avatarBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
parent 98416549

drivers/ide/ide-cd.c

+4 −119
Original line number Diff line number Diff line
@@ -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,
@@ -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
@@ -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 *);



/*
@@ -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);
@@ -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;

	}



	/*
@@ -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;
@@ -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);
@@ -2090,10 +1979,6 @@ 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);



	if (rc < 0)

drivers/ide/ide-cd.h

+0 −4
Original line number Diff line number Diff line
@@ -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;