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    Subject[RFC PATCH v2 20/21] btrfs: add support for read_iter and write_iter
    Date
    btrfs can use generic_file_read_iter(). Base btrfs_file_write_iter()
    on btrfs_file_aio_write(), then have the latter call the former.

    Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
    Cc: Zach Brown <zab@zabbo.net>
    Cc: Chris Mason <chris.mason@oracle.com>
    Cc: linux-btrfs@vger.kernel.org
    ---
    fs/btrfs/file.c | 55 ++++++++++++++++++++++++++++++-------------------------
    1 file changed, 30 insertions(+), 25 deletions(-)

    diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
    index e8d06b6..31275d1 100644
    --- a/fs/btrfs/file.c
    +++ b/fs/btrfs/file.c
    @@ -1285,20 +1285,17 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
    }

    static ssize_t __btrfs_direct_write(struct kiocb *iocb,
    - const struct iovec *iov,
    - unsigned long nr_segs, loff_t pos,
    - loff_t *ppos, size_t count, size_t ocount)
    + struct iov_iter *iter,
    + loff_t pos, loff_t *ppos, size_t count)
    {
    struct file *file = iocb->ki_filp;
    struct inode *inode = fdentry(file)->d_inode;
    - struct iov_iter i;
    ssize_t written;
    ssize_t written_buffered;
    loff_t endbyte;
    int err;

    - written = generic_file_direct_write(iocb, iov, &nr_segs, pos, ppos,
    - count, ocount);
    + written = generic_file_direct_write_iter(iocb, iter, pos, ppos, count);

    /*
    * the generic O_DIRECT will update in-memory i_size after the
    @@ -1317,8 +1314,7 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb,

    pos += written;
    count -= written;
    - iov_iter_init(&i, iov, nr_segs, count, written);
    - written_buffered = __btrfs_buffered_write(file, &i, pos);
    + written_buffered = __btrfs_buffered_write(file, iter, pos);
    if (written_buffered < 0) {
    err = written_buffered;
    goto out;
    @@ -1335,9 +1331,8 @@ out:
    return written ? written : err;
    }

    -static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
    - const struct iovec *iov,
    - unsigned long nr_segs, loff_t pos)
    +static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
    + struct iov_iter *iter, loff_t pos)
    {
    struct file *file = iocb->ki_filp;
    struct inode *inode = fdentry(file)->d_inode;
    @@ -1346,18 +1341,13 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
    u64 start_pos;
    ssize_t num_written = 0;
    ssize_t err = 0;
    - size_t count, ocount;
    + size_t count;

    vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

    mutex_lock(&inode->i_mutex);

    - err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
    - if (err) {
    - mutex_unlock(&inode->i_mutex);
    - goto out;
    - }
    - count = ocount;
    + count = iov_iter_count(iter);

    current->backing_dev_info = inode->i_mapping->backing_dev_info;
    err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
    @@ -1406,14 +1396,10 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
    }

    if (unlikely(file->f_flags & O_DIRECT)) {
    - num_written = __btrfs_direct_write(iocb, iov, nr_segs,
    - pos, ppos, count, ocount);
    + num_written = __btrfs_direct_write(iocb, iter, pos, ppos,
    + count);
    } else {
    - struct iov_iter i;
    -
    - iov_iter_init(&i, iov, nr_segs, count, num_written);
    -
    - num_written = __btrfs_buffered_write(file, &i, pos);
    + num_written = __btrfs_buffered_write(file, iter, pos);
    if (num_written > 0)
    *ppos = pos + num_written;
    }
    @@ -1443,6 +1429,23 @@ out:
    return num_written ? num_written : err;
    }

    +static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
    + const struct iovec *iov,
    + unsigned long nr_segs, loff_t pos)
    +{
    + struct iov_iter i;
    + int ret;
    + size_t count;
    +
    + ret = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
    + if (ret)
    + return ret;
    +
    + iov_iter_init(&i, iov, nr_segs, count, 0);
    +
    + return btrfs_file_write_iter(iocb, &i, pos);
    +}
    +
    int btrfs_release_file(struct inode *inode, struct file *filp)
    {
    /*
    @@ -1874,7 +1877,9 @@ const struct file_operations btrfs_file_operations = {
    .write = do_sync_write,
    .aio_read = generic_file_aio_read,
    .splice_read = generic_file_splice_read,
    + .read_iter = generic_file_read_iter,
    .aio_write = btrfs_file_aio_write,
    + .write_iter = btrfs_file_write_iter,
    .mmap = btrfs_file_mmap,
    .open = generic_file_open,
    .release = btrfs_release_file,
    --
    1.7.9.5


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