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    Subject[PATCH 08/10] ide-tape: simplify read/write functions
    Date
    Impact: cleanup

    idetape_chrdev_read/write() functions are unnecessarily complex when
    everything can be handled in a single loop. Collapse
    idetape_add_chrdev_read/write_request() into the rw functions and
    simplify the implementation.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    drivers/ide/ide-tape.c | 149 ++++++++++++++++--------------------------------
    1 files changed, 50 insertions(+), 99 deletions(-)

    diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
    index 5fc3282..95e9131 100644
    --- a/drivers/ide/ide-tape.c
    +++ b/drivers/ide/ide-tape.c
    @@ -953,14 +953,6 @@ static void idetape_create_space_cmd(struct ide_atapi_pc *pc, int count, u8 cmd)
    pc->flags |= PC_FLAG_WAIT_FOR_DSC;
    }

    -/* Queue up a character device originated write request. */
    -static int idetape_add_chrdev_write_request(ide_drive_t *drive, int size)
    -{
    - debug_log(DBG_CHRDEV, "Enter %s\n", __func__);
    -
    - return idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, size);
    -}
    -
    static void ide_tape_flush_merge_buffer(ide_drive_t *drive)
    {
    idetape_tape_t *tape = drive->driver_data;
    @@ -974,7 +966,7 @@ static void ide_tape_flush_merge_buffer(ide_drive_t *drive)
    size_t aligned = roundup(tape->valid, tape->blk_size);

    memset(tape->cur + tape->valid, 0, aligned - tape->valid);
    - idetape_add_chrdev_write_request(drive, aligned);
    + idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, aligned);
    kfree(tape->buf);
    tape->buf = NULL;
    }
    @@ -1027,20 +1019,6 @@ static int idetape_init_rw(ide_drive_t *drive, int dir)
    return 0;
    }

    -/* called from idetape_chrdev_read() to service a chrdev read request. */
    -static int idetape_add_chrdev_read_request(ide_drive_t *drive, int size)
    -{
    - debug_log(DBG_PROCS, "Enter %s, %d bytes\n", __func__, size);
    -
    - /* If we are at a filemark, return a read length of 0 */
    - if (test_bit(IDE_AFLAG_FILEMARK, &drive->atapi_flags))
    - return 0;
    -
    - idetape_init_rw(drive, IDETAPE_DIR_READ);
    -
    - return idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, size);
    -}
    -
    static void idetape_pad_zeros(ide_drive_t *drive, int bcount)
    {
    idetape_tape_t *tape = drive->driver_data;
    @@ -1180,8 +1158,9 @@ static ssize_t idetape_chrdev_read(struct file *file, char __user *buf,
    {
    struct ide_tape_obj *tape = file->private_data;
    ide_drive_t *drive = tape->drive;
    - ssize_t bytes_read, temp, actually_read = 0, rc;
    + size_t done = 0;
    ssize_t ret = 0;
    + int rc;

    debug_log(DBG_CHRDEV, "Enter %s, count %Zd\n", __func__, count);

    @@ -1191,52 +1170,43 @@ static ssize_t idetape_chrdev_read(struct file *file, char __user *buf,
    (count % tape->blk_size) == 0)
    tape->user_bs_factor = count / tape->blk_size;
    }
    +
    rc = idetape_init_rw(drive, IDETAPE_DIR_READ);
    if (rc < 0)
    return rc;
    - if (count == 0)
    - return (0);
    - if (tape->valid) {
    - actually_read = min_t(unsigned int, tape->valid, count);
    - if (copy_to_user(buf, tape->cur, actually_read))
    - ret = -EFAULT;
    - buf += actually_read;
    - count -= actually_read;
    - tape->cur += actually_read;
    - tape->valid -= actually_read;
    - }
    - while (count >= tape->buffer_size) {
    - bytes_read = idetape_add_chrdev_read_request(drive,
    - tape->buffer_size);
    - if (bytes_read <= 0)
    - goto finish;
    - if (copy_to_user(buf, tape->cur, bytes_read))
    - ret = -EFAULT;
    - buf += bytes_read;
    - count -= bytes_read;
    - actually_read += bytes_read;
    - }
    - if (count) {
    - bytes_read = idetape_add_chrdev_read_request(drive,
    - tape->buffer_size);
    - if (bytes_read <= 0)
    - goto finish;
    - temp = min((unsigned long)count, (unsigned long)bytes_read);
    - if (copy_to_user(buf, tape->cur, temp))
    +
    + while (done < count) {
    + size_t todo;
    +
    + /* refill if staging buffer is empty */
    + if (!tape->valid) {
    + /* If we are at a filemark, nothing more to read */
    + if (test_bit(IDE_AFLAG_FILEMARK, &drive->atapi_flags))
    + break;
    + /* read */
    + if (idetape_queue_rw_tail(drive, REQ_IDETAPE_READ,
    + tape->buffer_size) <= 0)
    + break;
    + }
    +
    + /* copy out */
    + todo = min_t(size_t, count - done, tape->valid);
    + if (copy_to_user(buf + done, tape->cur, todo))
    ret = -EFAULT;
    - actually_read += temp;
    - tape->cur += temp;
    - tape->valid -= temp;
    +
    + tape->cur += todo;
    + tape->valid -= todo;
    + done += todo;
    }
    -finish:
    - if (!actually_read && test_bit(IDE_AFLAG_FILEMARK, &drive->atapi_flags)) {
    +
    + if (!done && test_bit(IDE_AFLAG_FILEMARK, &drive->atapi_flags)) {
    debug_log(DBG_SENSE, "%s: spacing over filemark\n", tape->name);

    idetape_space_over_filemarks(drive, MTFSF, 1);
    return 0;
    }

    - return ret ? ret : actually_read;
    + return ret ? ret : done;
    }

    static ssize_t idetape_chrdev_write(struct file *file, const char __user *buf,
    @@ -1244,7 +1214,7 @@ static ssize_t idetape_chrdev_write(struct file *file, const char __user *buf,
    {
    struct ide_tape_obj *tape = file->private_data;
    ide_drive_t *drive = tape->drive;
    - ssize_t actually_written = 0;
    + size_t done = 0;
    ssize_t ret = 0;
    int rc;

    @@ -1258,47 +1228,28 @@ static ssize_t idetape_chrdev_write(struct file *file, const char __user *buf,
    rc = idetape_init_rw(drive, IDETAPE_DIR_WRITE);
    if (rc < 0)
    return rc;
    - if (count == 0)
    - return (0);
    - if (tape->valid < tape->buffer_size) {
    - actually_written = min_t(unsigned int,
    - tape->buffer_size - tape->valid,
    - count);
    - if (copy_from_user(tape->cur, buf, actually_written))
    - ret = -EFAULT;
    - buf += actually_written;
    - count -= actually_written;
    - tape->cur += actually_written;
    - tape->valid += actually_written;
    -
    - if (tape->valid == tape->buffer_size) {
    - ssize_t retval;
    - retval = idetape_add_chrdev_write_request(drive,
    - tape->buffer_size);
    - if (retval <= 0)
    - return (retval);
    - }
    - }
    - while (count >= tape->buffer_size) {
    - ssize_t retval;
    - if (copy_from_user(tape->cur, buf, tape->buffer_size))
    - ret = -EFAULT;
    - buf += tape->buffer_size;
    - count -= tape->buffer_size;
    - retval = idetape_add_chrdev_write_request(drive,
    - tape->buffer_size);
    - actually_written += tape->buffer_size;
    - if (retval <= 0)
    - return (retval);
    - }
    - if (count) {
    - actually_written += count;
    - if (copy_from_user(tape->cur, buf, count))
    +
    + while (done < count) {
    + size_t todo;
    +
    + /* flush if staging buffer is full */
    + if (tape->valid == tape->buffer_size &&
    + idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE,
    + tape->buffer_size) <= 0)
    + return rc;
    +
    + /* copy in */
    + todo = min_t(size_t, count - done,
    + tape->buffer_size - tape->valid);
    + if (copy_from_user(tape->cur, buf + done, todo))
    ret = -EFAULT;
    - tape->cur += count;
    - tape->valid += count;
    +
    + tape->cur += todo;
    + tape->valid += todo;
    + done += todo;
    }
    - return ret ? ret : actually_written;
    +
    + return ret ? ret : done;
    }

    static int idetape_write_filemark(ide_drive_t *drive)
    --
    1.6.0.2


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