From 73176bee9918a3738237b0e06eff72b497283869 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Mon, 7 Mar 2016 13:02:15 +0100 Subject: block: Fix snapshot=on cache modes Since commit 91a097e, we end up with a somewhat weird cache mode configuration with snapshot=on: The commit broke the cache mode inheritance for the snapshot overlay so that it is opened as writethrough instead of unsafe now. The following bdrv_append() call to put it on top of the tree swaps the WCE flag with the snapshot's backing file (i.e. the originally given file), so what we eventually get is cache=writeback on the temporary overlay and cache=writethrough,cache.no-flush=on on the real image file. This patch changes things so that the temporary overlay gets cache=unsafe again like it used to, and the real images get whatever the user specified. This means that cache.direct is now respected even with snapshot=on, and in the case of committing changes, the final flush is no longer ignored except explicitly requested by the user. Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz --- block.c | 36 +++++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 11 deletions(-) (limited to 'block.c') diff --git a/block.c b/block.c index ba24b8e674..cf5eb34382 100644 --- a/block.c +++ b/block.c @@ -687,13 +687,19 @@ int bdrv_parse_cache_flags(const char *mode, int *flags) } /* - * Returns the flags that a temporary snapshot should get, based on the - * originally requested flags (the originally requested image will have flags - * like a backing file) + * Returns the options and flags that a temporary snapshot should get, based on + * the originally requested flags (the originally requested image will have + * flags like a backing file) */ -static int bdrv_temp_snapshot_flags(int flags) +static void bdrv_temp_snapshot_options(int *child_flags, QDict *child_options, + int parent_flags, QDict *parent_options) { - return (flags & ~BDRV_O_SNAPSHOT) | BDRV_O_TEMPORARY; + *child_flags = (parent_flags & ~BDRV_O_SNAPSHOT) | BDRV_O_TEMPORARY; + + /* For temporary files, unconditional cache=unsafe is fine */ + qdict_set_default_str(child_options, BDRV_OPT_CACHE_WB, "on"); + qdict_set_default_str(child_options, BDRV_OPT_CACHE_DIRECT, "off"); + qdict_set_default_str(child_options, BDRV_OPT_CACHE_NO_FLUSH, "on"); } /* @@ -1424,13 +1430,13 @@ done: return c; } -int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp) +static int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, + QDict *snapshot_options, Error **errp) { /* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */ char *tmp_filename = g_malloc0(PATH_MAX + 1); int64_t total_size; QemuOpts *opts = NULL; - QDict *snapshot_options; BlockDriverState *bs_snapshot; Error *local_err = NULL; int ret; @@ -1464,8 +1470,7 @@ int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp) goto out; } - /* Prepare a new options QDict for the temporary file */ - snapshot_options = qdict_new(); + /* Prepare options QDict for the temporary file */ qdict_put(snapshot_options, "file.driver", qstring_from_str("file")); qdict_put(snapshot_options, "file.filename", @@ -1477,6 +1482,7 @@ int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp) ret = bdrv_open(&bs_snapshot, NULL, NULL, snapshot_options, flags, &local_err); + snapshot_options = NULL; if (ret < 0) { error_propagate(errp, local_err); goto out; @@ -1485,6 +1491,7 @@ int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp) bdrv_append(bs_snapshot, bs); out: + QDECREF(snapshot_options); g_free(tmp_filename); return ret; } @@ -1516,6 +1523,7 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename, const char *drvname; const char *backing; Error *local_err = NULL; + QDict *snapshot_options = NULL; int snapshot_flags = 0; assert(pbs); @@ -1607,7 +1615,9 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename, flags |= BDRV_O_ALLOW_RDWR; } if (flags & BDRV_O_SNAPSHOT) { - snapshot_flags = bdrv_temp_snapshot_flags(flags); + snapshot_options = qdict_new(); + bdrv_temp_snapshot_options(&snapshot_flags, snapshot_options, + flags, options); bdrv_backing_options(&flags, options, flags, options); } @@ -1709,7 +1719,9 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename, /* For snapshot=on, create a temporary qcow2 overlay. bs points to the * temporary snapshot afterwards. */ if (snapshot_flags) { - ret = bdrv_append_temp_snapshot(bs, snapshot_flags, &local_err); + ret = bdrv_append_temp_snapshot(bs, snapshot_flags, snapshot_options, + &local_err); + snapshot_options = NULL; if (local_err) { goto close_and_fail; } @@ -1721,6 +1733,7 @@ fail: if (file != NULL) { bdrv_unref_child(bs, file); } + QDECREF(snapshot_options); QDECREF(bs->explicit_options); QDECREF(bs->options); QDECREF(options); @@ -1743,6 +1756,7 @@ close_and_fail: } else { bdrv_unref(bs); } + QDECREF(snapshot_options); QDECREF(options); if (local_err) { error_propagate(errp, local_err); -- cgit v1.2.3