From 60065cb41272144762ceb38e9bcd1a203c29c064 Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

Date: Thu, 10 Jan 2019 12:44:34 +0000

Subject: [PATCH 04/14] block: Require auto-read-only for existing fallbacks

RH-Author: Kevin Wolf <kwolf@redhat.com>

Message-id: <20190110124442.30132-5-kwolf@redhat.com>

Patchwork-id: 83954

O-Subject: [RHEL-8.0 qemu-kvm PATCH 04/12] block: Require auto-read-only for existing fallbacks

Bugzilla: 1644996

RH-Acked-by: Max Reitz <mreitz@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Eric Blake <eblake@redhat.com>

Some block drivers have traditionally changed their node to read-only

mode without asking the user. This behaviour has been marked deprecated

since 2.11, expecting users to provide an explicit read-only=on option.

Now that we have auto-read-only=on, enable these drivers to make use of

the option.

This is the only use of bdrv_set_read_only(), so we can make it a bit

more specific and turn it into a bdrv_apply_auto_read_only() that is

more convenient for drivers to use.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Reviewed-by: Eric Blake <eblake@redhat.com>

(cherry picked from commit eaa2410f1ea864609090c0a5fda9e0ce9499da79)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 block.c               | 42 +++++++++++++++++++++++++++---------------

 block/bochs.c         | 17 ++++++-----------

 block/cloop.c         | 16 +++++-----------

 block/dmg.c           | 16 +++++-----------

 block/rbd.c           | 15 ++++-----------

 block/vvfat.c         | 10 ++--------

 include/block/block.h |  3 ++-

 7 files changed, 51 insertions(+), 68 deletions(-)

diff --git a/block.c b/block.c

index f357975..268debe 100644

--- a/block.c

+++ b/block.c

@@ -266,29 +266,41 @@ int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,

     return 0;

 }

-/* TODO Remove (deprecated since 2.11)

- * Block drivers are not supposed to automatically change bs->read_only.

- * Instead, they should just check whether they can provide what the user

- * explicitly requested and error out if read-write is requested, but they can

- * only provide read-only access. */

-int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp)

+/*

+ * Called by a driver that can only provide a read-only image.

+ *

+ * Returns 0 if the node is already read-only or it could switch the node to

+ * read-only because BDRV_O_AUTO_RDONLY is set.

+ *

+ * Returns -EACCES if the node is read-write and BDRV_O_AUTO_RDONLY is not set

+ * or bdrv_can_set_read_only() forbids making the node read-only. If @errmsg

+ * is not NULL, it is used as the error message for the Error object.

+ */

+int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,

+                              Error **errp)

 {

     int ret = 0;

-    ret = bdrv_can_set_read_only(bs, read_only, false, errp);

-    if (ret < 0) {

-        return ret;

+    if (!(bs->open_flags & BDRV_O_RDWR)) {

+        return 0;

+    }

+    if (!(bs->open_flags & BDRV_O_AUTO_RDONLY)) {

+        goto fail;

     }

-    bs->read_only = read_only;

-

-    if (read_only) {

-        bs->open_flags &= ~BDRV_O_RDWR;

-    } else {

-        bs->open_flags |= BDRV_O_RDWR;

+    ret = bdrv_can_set_read_only(bs, true, false, NULL);

+    if (ret < 0) {

+        goto fail;

     }

+    bs->read_only = true;

+    bs->open_flags &= ~BDRV_O_RDWR;

+

     return 0;

+

+fail:

+    error_setg(errp, "%s", errmsg ?: "Image is read-only");

+    return -EACCES;

 }

 void bdrv_get_full_backing_filename_from_filename(const char *backed,

diff --git a/block/bochs.c b/block/bochs.c

index 50c6300..22e7d44 100644

--- a/block/bochs.c

+++ b/block/bochs.c

@@ -105,23 +105,18 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,

     struct bochs_header bochs;

     int ret;

+    /* No write support yet */

+    ret = bdrv_apply_auto_read_only(bs, NULL, errp);

+    if (ret < 0) {

+        return ret;

+    }

+

     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,

                                false, errp);

     if (!bs->file) {

         return -EINVAL;

     }

-    if (!bdrv_is_read_only(bs)) {

-        error_report("Opening bochs images without an explicit read-only=on "

-                     "option is deprecated. Future versions will refuse to "

-                     "open the image instead of automatically marking the "

-                     "image read-only.");

-        ret = bdrv_set_read_only(bs, true, errp); /* no write support yet */

-        if (ret < 0) {

-            return ret;

-        }

-    }

-

     ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));

     if (ret < 0) {

         return ret;

diff --git a/block/cloop.c b/block/cloop.c

index 2be6898..df2b85f 100644

--- a/block/cloop.c

+++ b/block/cloop.c

@@ -67,23 +67,17 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,

     uint32_t offsets_size, max_compressed_block_size = 1, i;

     int ret;

+    ret = bdrv_apply_auto_read_only(bs, NULL, errp);

+    if (ret < 0) {

+        return ret;

+    }

+

     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,

                                false, errp);

     if (!bs->file) {

         return -EINVAL;

     }

-    if (!bdrv_is_read_only(bs)) {

-        error_report("Opening cloop images without an explicit read-only=on "

-                     "option is deprecated. Future versions will refuse to "

-                     "open the image instead of automatically marking the "

-                     "image read-only.");

-        ret = bdrv_set_read_only(bs, true, errp);

-        if (ret < 0) {

-            return ret;

-        }

-    }

-

     /* read header */

     ret = bdrv_pread(bs->file, 128, &s->block_size, 4);

     if (ret < 0) {

diff --git a/block/dmg.c b/block/dmg.c

index c9b3c51..1d9283b 100644

--- a/block/dmg.c

+++ b/block/dmg.c

@@ -413,23 +413,17 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,

     int64_t offset;

     int ret;

+    ret = bdrv_apply_auto_read_only(bs, NULL, errp);

+    if (ret < 0) {

+        return ret;

+    }

+

     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,

                                false, errp);

     if (!bs->file) {

         return -EINVAL;

     }

-    if (!bdrv_is_read_only(bs)) {

-        error_report("Opening dmg images without an explicit read-only=on "

-                     "option is deprecated. Future versions will refuse to "

-                     "open the image instead of automatically marking the "

-                     "image read-only.");

-        ret = bdrv_set_read_only(bs, true, errp);

-        if (ret < 0) {

-            return ret;

-        }

-    }

-

     block_module_load_one("dmg-bz2");

     s->n_chunks = 0;

diff --git a/block/rbd.c b/block/rbd.c

index dc369d0..8d74a29 100644

--- a/block/rbd.c

+++ b/block/rbd.c

@@ -773,17 +773,10 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,

     /* If we are using an rbd snapshot, we must be r/o, otherwise

      * leave as-is */

     if (s->snap != NULL) {

-        if (!bdrv_is_read_only(bs)) {

-            error_report("Opening rbd snapshots without an explicit "

-                         "read-only=on option is deprecated. Future versions "

-                         "will refuse to open the image instead of "

-                         "automatically marking the image read-only.");

-            r = bdrv_set_read_only(bs, true, &local_err);

-            if (r < 0) {

-                rbd_close(s->image);

-                error_propagate(errp, local_err);

-                goto failed_open;

-            }

+        r = bdrv_apply_auto_read_only(bs, "rbd snapshots are read-only", errp);

+        if (r < 0) {

+            rbd_close(s->image);

+            goto failed_open;

         }

     }

diff --git a/block/vvfat.c b/block/vvfat.c

index 3efce9e..a5a3fb9 100644

--- a/block/vvfat.c

+++ b/block/vvfat.c

@@ -1262,15 +1262,9 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,

                        "Unable to set VVFAT to 'rw' when drive is read-only");

             goto fail;

         }

-    } else  if (!bdrv_is_read_only(bs)) {

-        error_report("Opening non-rw vvfat images without an explicit "

-                     "read-only=on option is deprecated. Future versions "

-                     "will refuse to open the image instead of "

-                     "automatically marking the image read-only.");

-        /* read only is the default for safety */

-        ret = bdrv_set_read_only(bs, true, &local_err);

+    } else {

+        ret = bdrv_apply_auto_read_only(bs, NULL, errp);

         if (ret < 0) {

-            error_propagate(errp, local_err);

             goto fail;

         }

     }

diff --git a/include/block/block.h b/include/block/block.h

index 6ee8b2a..36a702c 100644

--- a/include/block/block.h

+++ b/include/block/block.h

@@ -433,7 +433,8 @@ int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,

 bool bdrv_is_read_only(BlockDriverState *bs);

 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,

                            bool ignore_allow_rdw, Error **errp);

-int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp);

+int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,

+                              Error **errp);

 bool bdrv_is_writable(BlockDriverState *bs);

 bool bdrv_is_sg(BlockDriverState *bs);

 bool bdrv_is_inserted(BlockDriverState *bs);

-- 

1.8.3.1