Commit f500a6d3 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

block: Avoid second open for format probing 



This fixes problems that are caused by the additional open/close cycle
of the existing format probing, for example related to qemu-nbd without
-t option or file descriptor passing.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 7b272452

block.c

+38 −28
Original line number Diff line number Diff line
@@ -518,22 +518,16 @@ BlockDriver *bdrv_find_protocol(const char *filename) 
    return NULL;

}



static int find_image_format(const char *filename, BlockDriver **pdrv)

static int find_image_format(BlockDriverState *bs, const char *filename,

                             BlockDriver **pdrv)

{

    int ret, score, score_max;

    int score, score_max;

    BlockDriver *drv1, *drv;

    uint8_t buf[2048];

    BlockDriverState *bs;



    ret = bdrv_file_open(&bs, filename, 0);

    if (ret < 0) {

        *pdrv = NULL;

        return ret;

    }

    int ret = 0;



    /* Return the raw BlockDriver * to scsi-generic devices or empty drives */

    if (bs->sg || !bdrv_is_inserted(bs)) {

        bdrv_delete(bs);

        drv = bdrv_find_format("raw");

        if (!drv) {

            ret = -ENOENT;
@@ -543,7 +537,6 @@ static int find_image_format(const char *filename, BlockDriver **pdrv) 
    }



    ret = bdrv_pread(bs, 0, buf, sizeof(buf));

    bdrv_delete(bs);

    if (ret < 0) {

        *pdrv = NULL;

        return ret;
@@ -657,7 +650,8 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags) 
/*

 * Common part for opening disk images and files

 */

static int bdrv_open_common(BlockDriverState *bs, const char *filename,

static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,

    const char *filename,

    int flags, BlockDriver *drv)

{

    int ret, open_flags;
@@ -691,13 +685,17 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename, 


    /* Open the image, either directly or using a protocol */

    if (drv->bdrv_file_open) {

        if (file != NULL) {

            bdrv_swap(file, bs);

            ret = 0;

        } else {

            ret = drv->bdrv_file_open(bs, filename, open_flags);

        }

    } else {

        ret = bdrv_file_open(&bs->file, filename, open_flags);

        if (ret >= 0) {

        assert(file != NULL);

        bs->file = file;

        ret = drv->bdrv_open(bs, open_flags);

    }

    }



    if (ret < 0) {

        goto free_and_fail;
@@ -716,10 +714,7 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename, 
    return 0;



free_and_fail:

    if (bs->file) {

        bdrv_delete(bs->file);

    bs->file = NULL;

    }

    g_free(bs->opaque);

    bs->opaque = NULL;

    bs->drv = NULL;
@@ -741,7 +736,7 @@ int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags) 
    }



    bs = bdrv_new("");

    ret = bdrv_open_common(bs, filename, flags, drv);

    ret = bdrv_open_common(bs, NULL, filename, flags, drv);

    if (ret < 0) {

        bdrv_delete(bs);

        return ret;
@@ -796,6 +791,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags, 
    int ret;

    /* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */

    char tmp_filename[PATH_MAX + 1];

    BlockDriverState *file = NULL;



    if (flags & BDRV_O_SNAPSHOT) {

        BlockDriverState *bs1;
@@ -855,25 +851,36 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags, 
        bs->is_temporary = 1;

    }



    /* Open image file without format layer */

    if (flags & BDRV_O_RDWR) {

        flags |= BDRV_O_ALLOW_RDWR;

    }



    ret = bdrv_file_open(&file, filename, bdrv_open_flags(bs, flags));

    if (ret < 0) {

        return ret;

    }



    /* Find the right image format driver */

    if (!drv) {

        ret = find_image_format(filename, &drv);

        ret = find_image_format(file, filename, &drv);

    }



    if (!drv) {

        goto unlink_and_fail;

    }



    if (flags & BDRV_O_RDWR) {

        flags |= BDRV_O_ALLOW_RDWR;

    }



    /* Open the image */

    ret = bdrv_open_common(bs, filename, flags, drv);

    ret = bdrv_open_common(bs, file, filename, flags, drv);

    if (ret < 0) {

        goto unlink_and_fail;

    }



    if (bs->file != file) {

        bdrv_delete(file);

        file = NULL;

    }



    /* If there is a backing file, use it */

    if ((flags & BDRV_O_NO_BACKING) == 0) {

        ret = bdrv_open_backing_file(bs);
@@ -895,6 +902,9 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags, 
    return 0;



unlink_and_fail:

    if (file != NULL) {

        bdrv_delete(file);

    }

    if (bs->is_temporary) {

        unlink(filename);

    }