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block: Add "read-only" to the options QDict 

This adds the "read-only" option to the QDict. One important effect of
this change is that when a child inherits options from its parent, the
existing "read-only" mode can be preserved if it was explicitly set
previously.

This addresses scenarios like this:

   [E] <- [D] <- [C] <- [B] <- [A]

In this case, if we reopen [D] with read-only=off, and later reopen
[B], then [D] will not inherit read-only=on from its parent during the
bdrv_reopen_queue_child() stage.

The BDRV_O_RDWR flag is not removed yet, but its keep in sync with the
value of the "read-only" option.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Alberto Garcia 2016-09-15 17:53:02 +03:00 committed by Kevin Wolf
parent 9b7e869167
commit f87a0e29a9
4 changed files with 45 additions and 13 deletions
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38
block.c
View File

@ -733,6 +733,9 @@ static void bdrv_temp_snapshot_options(int *child_flags, QDict *child_options,
qdict_set_default_str(child_options, BDRV_OPT_CACHE_DIRECT, "off");
qdict_set_default_str(child_options, BDRV_OPT_CACHE_NO_FLUSH, "on");
/* Copy the read-only option from the parent */
qdict_copy_default(child_options, parent_options, BDRV_OPT_READ_ONLY);
/* aio=native doesn't work for cache.direct=off, so disable it for the
* temporary snapshot */
*child_flags &= ~BDRV_O_NATIVE_AIO;
@ -755,6 +758,9 @@ static void bdrv_inherited_options(int *child_flags, QDict *child_options,
qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_DIRECT);
qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_NO_FLUSH);
/* Inherit the read-only option from the parent if it's not set */
qdict_copy_default(child_options, parent_options, BDRV_OPT_READ_ONLY);
/* Our block drivers take care to send flushes and respect unmap policy,
* so we can default to enable both on lower layers regardless of the
* corresponding parent options. */
@ -808,7 +814,8 @@ static void bdrv_backing_options(int *child_flags, QDict *child_options,
qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_NO_FLUSH);
/* backing files always opened read-only */
flags &= ~(BDRV_O_RDWR | BDRV_O_COPY_ON_READ);
qdict_set_default_str(child_options, BDRV_OPT_READ_ONLY, "on");
flags &= ~BDRV_O_COPY_ON_READ;
/* snapshot=on is handled on the top layer */
flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_TEMPORARY);
@ -855,6 +862,14 @@ static void update_flags_from_options(int *flags, QemuOpts *opts)
if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_DIRECT, false)) {
*flags |= BDRV_O_NOCACHE;
}
*flags &= ~BDRV_O_RDWR;
assert(qemu_opt_find(opts, BDRV_OPT_READ_ONLY));
if (!qemu_opt_get_bool(opts, BDRV_OPT_READ_ONLY, false)) {
*flags |= BDRV_O_RDWR;
}
}
static void update_options_from_flags(QDict *options, int flags)
@ -867,6 +882,10 @@ static void update_options_from_flags(QDict *options, int flags)
qdict_put(options, BDRV_OPT_CACHE_NO_FLUSH,
qbool_from_bool(flags & BDRV_O_NO_FLUSH));
}
if (!qdict_haskey(options, BDRV_OPT_READ_ONLY)) {
qdict_put(options, BDRV_OPT_READ_ONLY,
qbool_from_bool(!(flags & BDRV_O_RDWR)));
}
}
static void bdrv_assign_node_name(BlockDriverState *bs,
@ -930,6 +949,11 @@ static QemuOptsList bdrv_runtime_opts = {
.type = QEMU_OPT_BOOL,
.help = "Ignore flush requests",
},
{
.name = BDRV_OPT_READ_ONLY,
.type = QEMU_OPT_BOOL,
.help = "Node is opened in read-only mode",
},
{ /* end of list */ }
},
};
@ -1674,14 +1698,22 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
goto fail;
}
if (flags & BDRV_O_RDWR) {
flags |= BDRV_O_ALLOW_RDWR;
/* Set the BDRV_O_RDWR and BDRV_O_ALLOW_RDWR flags.
* FIXME: we're parsing the QDict to avoid having to create a
* QemuOpts just for this, but neither option is optimal. */
if (g_strcmp0(qdict_get_try_str(options, BDRV_OPT_READ_ONLY), "on") &&
!qdict_get_try_bool(options, BDRV_OPT_READ_ONLY, false)) {
flags |= (BDRV_O_RDWR | BDRV_O_ALLOW_RDWR);
} else {
flags &= ~BDRV_O_RDWR;
}
if (flags & BDRV_O_SNAPSHOT) {
snapshot_options = qdict_new();
bdrv_temp_snapshot_options(&snapshot_flags, snapshot_options,
flags, options);
/* Let bdrv_backing_options() override "read-only" */
qdict_del(options, BDRV_OPT_READ_ONLY);
bdrv_backing_options(&flags, options, flags, options);
}

3
block/vvfat.c
View File

@ -2971,7 +2971,8 @@ static BlockDriver vvfat_write_target = {
static void vvfat_qcow_options(int *child_flags, QDict *child_options,
int parent_flags, QDict *parent_options)
{
*child_flags = BDRV_O_RDWR | BDRV_O_NO_FLUSH;
qdict_set_default_str(child_options, BDRV_OPT_READ_ONLY, "off");
*child_flags = BDRV_O_NO_FLUSH;
}
static const BdrvChildRole child_vvfat_qcow = {

16
blockdev.c
View File

@ -360,9 +360,6 @@ static void extract_common_blockdev_options(QemuOpts *opts, int *bdrv_flags,
const char *aio;
if (bdrv_flags) {
if (!qemu_opt_get_bool(opts, "read-only", false)) {
*bdrv_flags |= BDRV_O_RDWR;
}
if (qemu_opt_get_bool(opts, "copy-on-read", false)) {
*bdrv_flags |= BDRV_O_COPY_ON_READ;
}
@ -471,7 +468,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
int bdrv_flags = 0;
int on_read_error, on_write_error;
bool account_invalid, account_failed;
bool writethrough;
bool writethrough, read_only;
BlockBackend *blk;
BlockDriverState *bs;
ThrottleConfig cfg;
@ -567,6 +564,8 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
bdrv_flags |= BDRV_O_SNAPSHOT;
}
read_only = qemu_opt_get_bool(opts, BDRV_OPT_READ_ONLY, false);
/* init */
if ((!file || !*file) && !qdict_size(bs_opts)) {
BlockBackendRootState *blk_rs;
@ -574,7 +573,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
blk = blk_new();
blk_rs = blk_get_root_state(blk);
blk_rs->open_flags = bdrv_flags;
blk_rs->read_only = !(bdrv_flags & BDRV_O_RDWR);
blk_rs->read_only = read_only;
blk_rs->detect_zeroes = detect_zeroes;
QDECREF(bs_opts);
@ -588,6 +587,8 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
* Apply the defaults here instead. */
qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_DIRECT, "off");
qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_NO_FLUSH, "off");
qdict_set_default_str(bs_opts, BDRV_OPT_READ_ONLY,
read_only ? "on" : "off");
assert((bdrv_flags & BDRV_O_CACHE_MASK) == 0);
if (runstate_check(RUN_STATE_INMIGRATE)) {
@ -682,6 +683,7 @@ static BlockDriverState *bds_tree_init(QDict *bs_opts, Error **errp)
* Apply the defaults here instead. */
qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_DIRECT, "off");
qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_NO_FLUSH, "off");
qdict_set_default_str(bs_opts, BDRV_OPT_READ_ONLY, "off");
if (runstate_check(RUN_STATE_INMIGRATE)) {
bdrv_flags |= BDRV_O_INACTIVE;
@ -4158,10 +4160,6 @@ static QemuOptsList qemu_root_bds_opts = {
.name = "aio",
.type = QEMU_OPT_STRING,
.help = "host AIO implementation (threads, native)",
},{
.name = "read-only",
.type = QEMU_OPT_BOOL,
.help = "open drive file as read-only",
},{
.name = "copy-on-read",
.type = QEMU_OPT_BOOL,

1
include/block/block.h
View File

@ -107,6 +107,7 @@ typedef struct HDGeometry {
#define BDRV_OPT_CACHE_WB "cache.writeback"
#define BDRV_OPT_CACHE_DIRECT "cache.direct"
#define BDRV_OPT_CACHE_NO_FLUSH "cache.no-flush"
#define BDRV_OPT_READ_ONLY "read-only"
#define BDRV_SECTOR_BITS 9