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: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index fe5aefbf83392fae89553050dd484dcf108fd428..5163f6069f8a1461dff96de149118767c588cd7a 100644 (file)
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -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);
@@ -2090,11 +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);

diff --git a/drivers/ide/ide-cd.h b/drivers/ide/ide-cd.h
index 22e3751a681e0ce627aa1fb21cb95a88de298f8a..a58801c4484d309177afe8b7d32aa77c7ac7f91f 100644 (file)
--- a/drivers/ide/ide-cd.h
+++ b/drivers/ide/ide-cd.h
@@ -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;