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From 31c90390db10329e2e7da072492fa7ec728abed0 Mon Sep 17 00:00:00 2001
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From: Jeffrey Cody <jcody@redhat.com>
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Date: Tue, 11 Feb 2014 16:14:26 +0100
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Subject: [PATCH 20/28] block: resize backing image during active layer commit, if needed
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RH-Author: Jeffrey Cody <jcody@redhat.com>
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Message-id: <b725bb85bfb2d59275a3a8b1a6c3c2c6341567c3.1392134912.git.jcody@redhat.com>
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Patchwork-id: 57216
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O-Subject: [RHEL7 qemu-kvm PATCH 2/6] block: resize backing image during active layer commit, if needed
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Bugzilla: 1047254
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Markus Armbruster <armbru@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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If the top image to commit is the active layer, and also larger than
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the base image, then an I/O error will likely be returned during
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block-commit.
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For instance, if we have a base image with a virtual size 10G, and a
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active layer image of size 20G, then committing the snapshot via
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'block-commit' will likely fail.
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This will automatically attempt to resize the base image, if the
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active layer image to be committed is larger.
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Signed-off-by: Jeff Cody <jcody@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Benoit Canet <benoit@irqsave.net>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 4da83585961631bfc10831dd26c4afda2a8b23e8)
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---
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 block/mirror.c | 38 ++++++++++++++++++++++++++++++++++++++
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 1 file changed, 38 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 block/mirror.c |   38 ++++++++++++++++++++++++++++++++++++++
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 1 files changed, 38 insertions(+), 0 deletions(-)
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diff --git a/block/mirror.c b/block/mirror.c
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index 6e1f9b1..ba1428b 100644
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--- a/block/mirror.c
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+++ b/block/mirror.c
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@@ -627,11 +627,49 @@ void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
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                          BlockDriverCompletionFunc *cb,
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                          void *opaque, Error **errp)
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 {
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+    int64_t length, base_length;
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+    int orig_base_flags;
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+
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+    orig_base_flags = bdrv_get_flags(base);
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+
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     if (bdrv_reopen(base, bs->open_flags, errp)) {
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         return;
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     }
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+
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+    length = bdrv_getlength(bs);
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+    if (length < 0) {
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+        error_setg(errp, "Unable to determine length of %s", bs->filename);
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+        goto error_restore_flags;
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+    }
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+
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+    base_length = bdrv_getlength(base);
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+    if (base_length < 0) {
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+        error_setg(errp, "Unable to determine length of %s", base->filename);
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+        goto error_restore_flags;
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+    }
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+
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+    if (length > base_length) {
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+        if (bdrv_truncate(base, length) < 0) {
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+            error_setg(errp, "Top image %s is larger than base image %s, and "
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+                             "resize of base image failed",
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+                             bs->filename, base->filename);
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+            goto error_restore_flags;
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+        }
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+    }
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+
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     bdrv_ref(base);
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     mirror_start_job(bs, base, speed, 0, 0,
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                      on_error, on_error, cb, opaque, errp,
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                      &commit_active_job_driver, false, base);
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+    if (error_is_set(errp)) {
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+        goto error_restore_flags;
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+    }
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+
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+    return;
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+
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+error_restore_flags:
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+    /* ignore error and errp for bdrv_reopen, because we want to propagate
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+     * the original error */
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+    bdrv_reopen(base, orig_base_flags, NULL);
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+    return;
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 }
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-- 
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1.7.1
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