From 398e6ad014df261d20d3fd6cff2cfbf940bac714 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 7 Nov 2017 18:21:41 +0100 Subject: block: Deprecate bdrv_set_read_only() and users bdrv_set_read_only() is used by some block drivers to override the read-only option given by the user. This is not how read-only images generally work in QEMU: Instead of second guessing what the user really meant (which currently includes making an image read-only even if the user didn't only use the default, but explicitly said read-only=off), we should error out if we can't provide what the user requested. This adds deprecation warnings to all callers of bdrv_set_read_only() so that the behaviour can be corrected after the usual deprecation period. Signed-off-by: Kevin Wolf --- block.c | 5 +++++ block/bochs.c | 13 ++++++++++--- block/cloop.c | 13 ++++++++++--- block/dmg.c | 12 +++++++++--- block/rbd.c | 14 ++++++++++---- block/vvfat.c | 6 +++++- qapi/block-core.json | 7 +++++-- 7 files changed, 54 insertions(+), 16 deletions(-) diff --git a/block.c b/block.c index f6415547fe..0ed0c27140 100644 --- a/block.c +++ b/block.c @@ -261,6 +261,11 @@ 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) { int ret = 0; diff --git a/block/bochs.c b/block/bochs.c index a759b6eff0..50c630047b 100644 --- a/block/bochs.c +++ b/block/bochs.c @@ -28,6 +28,7 @@ #include "block/block_int.h" #include "qemu/module.h" #include "qemu/bswap.h" +#include "qemu/error-report.h" /**************************************************************/ @@ -110,9 +111,15 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags, return -EINVAL; } - ret = bdrv_set_read_only(bs, true, errp); /* no write support yet */ - if (ret < 0) { - return ret; + 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)); diff --git a/block/cloop.c b/block/cloop.c index d6597fcf78..2be68987bd 100644 --- a/block/cloop.c +++ b/block/cloop.c @@ -23,6 +23,7 @@ */ #include "qemu/osdep.h" #include "qapi/error.h" +#include "qemu/error-report.h" #include "qemu-common.h" #include "block/block_int.h" #include "qemu/module.h" @@ -72,9 +73,15 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags, return -EINVAL; } - ret = bdrv_set_read_only(bs, true, errp); - if (ret < 0) { - return ret; + 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 */ diff --git a/block/dmg.c b/block/dmg.c index 6c0711f563..c9b3c519c4 100644 --- a/block/dmg.c +++ b/block/dmg.c @@ -419,9 +419,15 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags, return -EINVAL; } - ret = bdrv_set_read_only(bs, true, errp); - if (ret < 0) { - return ret; + 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"); diff --git a/block/rbd.c b/block/rbd.c index 144f350e1f..a76a5e8755 100644 --- a/block/rbd.c +++ b/block/rbd.c @@ -665,10 +665,16 @@ 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) { - r = bdrv_set_read_only(bs, true, &local_err); - if (r < 0) { - error_propagate(errp, local_err); - goto failed_open; + 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) { + error_propagate(errp, local_err); + goto failed_open; + } } } diff --git a/block/vvfat.c b/block/vvfat.c index a0f2335894..0841cc42fc 100644 --- a/block/vvfat.c +++ b/block/vvfat.c @@ -1259,7 +1259,11 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags, "Unable to set VVFAT to 'rw' when drive is read-only"); goto fail; } - } else { + } 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); if (ret < 0) { diff --git a/qapi/block-core.json b/qapi/block-core.json index ab96e348e6..76bf50f813 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -3134,8 +3134,11 @@ # This option is required on the top level of blockdev-add. # @discard: discard-related options (default: ignore) # @cache: cache-related options -# @read-only: whether the block device should be read-only -# (default: false) +# @read-only: whether the block device should be read-only (default: false). +# Note that some block drivers support only read-only access, +# either generally or in certain configurations. In this case, +# the default value does not work and the option must be +# specified explicitly. # @detect-zeroes: detect and optimize zero writes (Since 2.1) # (default: off) # @force-share: force share all permission on added nodes. -- cgit v1.2.1