Commit ceb42de8 authored by Anthony Liguori's avatar Anthony Liguori
Browse files

native preadv/pwritev support (Christoph Hellwig) 



This ties up the preadv/pwritev syscalls to qemu if they are declared in
unistd.h.  This is the case currently on at least NetBSD and OpenBSD and
will hopefully soon be the case on Linux.

Thanks to Blue Swirl and Gerd Hoffmann for the configure autodetection
of preadv/pwritev.


Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7021 c046a42c-6fe2-441c-8c8c-71466251a162
parent f141eafe

block.c

+1 −2
Original line number Diff line number Diff line
@@ -1354,10 +1354,9 @@ static void bdrv_aio_bh_cb(void *opaque) 
{

    BlockDriverAIOCBSync *acb = opaque;



    qemu_vfree(acb->bounce);



    if (!acb->is_write)

        qemu_iovec_from_buffer(acb->qiov, acb->bounce, acb->qiov->size);

    qemu_vfree(acb->bounce);

    acb->common.cb(acb->common.opaque, acb->ret);



    qemu_aio_release(acb);

configure

+17 −0
Original line number Diff line number Diff line
@@ -1107,6 +1107,19 @@ if $cc $ARCH_CFLAGS -o $TMPE $TMPC > /dev/null 2> /dev/null ; then 
  iovec=yes

fi



##########################################

# preadv probe

cat > $TMPC <<EOF

#include <sys/types.h>

#include <sys/uio.h>

#include <unistd.h>

int main(void) { preadv; }

EOF

preadv=no

if $cc $ARCH_CFLAGS -o $TMPE $TMPC > /dev/null 2> /dev/null ; then

  preadv=yes

fi



##########################################

# fdt probe

if test "$fdt" = "yes" ; then
@@ -1221,6 +1234,7 @@ echo "AIO support $aio" 
echo "Install blobs     $blobs"

echo "KVM support       $kvm"

echo "fdt support       $fdt"

echo "preadv support    $preadv"



if test $sdl_too_old = "yes"; then

echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -1522,6 +1536,9 @@ fi 
if test "$iovec" = "yes" ; then

  echo "#define HAVE_IOVEC 1" >> $config_h

fi

if test "$preadv" = "yes" ; then

  echo "#define HAVE_PREADV 1" >> $config_h

fi

if test "$fdt" = "yes" ; then

  echo "#define HAVE_FDT 1" >> $config_h

  echo "FDT_LIBS=-lfdt" >> $config_mak

posix-aio-compat.c

+83 −2
Original line number Diff line number Diff line
@@ -33,6 +33,12 @@ static int cur_threads = 0; 
static int idle_threads = 0;

static TAILQ_HEAD(, qemu_paiocb) request_list;



#ifdef HAVE_PREADV

static int preadv_present = 1;

#else

static int preadv_present = 0;

#endif



static void die2(int err, const char *what)

{

    fprintf(stderr, "%s failed: %s\n", what, strerror(err));
@@ -87,6 +93,36 @@ static size_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb) 
	return ret;

}



#ifdef HAVE_PREADV



static ssize_t

qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return preadv(fd, iov, nr_iov, offset);

}



static ssize_t

qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return pwritev(fd, iov, nr_iov, offset);

}



#else



static ssize_t

qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return -ENOSYS;

}



static ssize_t

qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)

{

    return -ENOSYS;

}



#endif



/*

 * Check if we need to copy the data in the aiocb into a new

 * properly aligned buffer.
@@ -104,6 +140,29 @@ static int aiocb_needs_copy(struct qemu_paiocb *aiocb) 
    return 0;

}



static size_t handle_aiocb_rw_vector(struct qemu_paiocb *aiocb)

{

    size_t offset = 0;

    ssize_t len;



    do {

        if (aiocb->aio_type == QEMU_PAIO_WRITE)

            len = qemu_pwritev(aiocb->aio_fildes,

                               aiocb->aio_iov,

                               aiocb->aio_niov,

                               aiocb->aio_offset + offset);

         else

            len = qemu_preadv(aiocb->aio_fildes,

                              aiocb->aio_iov,

                              aiocb->aio_niov,

                              aiocb->aio_offset + offset);

    } while (len == -1 && errno == EINTR);



    if (len == -1)

        return -errno;

    return len;

}



static size_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf)

{

    size_t offset = 0;
@@ -140,12 +199,34 @@ static size_t handle_aiocb_rw(struct qemu_paiocb *aiocb) 
    size_t nbytes;

    char *buf;



    if (!aiocb_needs_copy(aiocb) && aiocb->aio_niov == 1) {

    if (!aiocb_needs_copy(aiocb)) {

        /*

         * If there is just a single buffer, and it is properly aligned

         * we can just use plain pread/pwrite without any problems.

         */

        if (aiocb->aio_niov == 1)

             return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base);



        /*

         * We have more than one iovec, and all are properly aligned.

         *

         * Try preadv/pwritev first and fall back to linearizing the

         * buffer if it's not supported.

         */

	if (preadv_present) {

            nbytes = handle_aiocb_rw_vector(aiocb);

            if (nbytes == aiocb->aio_nbytes)

	        return nbytes;

            if (nbytes < 0 && nbytes != -ENOSYS)

                return nbytes;

            preadv_present = 0;

        }



        /*

         * XXX(hch): short read/write.  no easy way to handle the reminder

         * using these interfaces.  For now retry using plain

         * pread/pwrite?

         */

    }



    /*