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From 2f66e62873ef54bd27ec6e063c8b4f3f11e2413d Mon Sep 17 00:00:00 2001
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From: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
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Date: Mon, 10 Mar 2014 17:41:43 +0100
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Subject: [PATCH 15/16] qemu_file: use fwrite() correctly
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RH-Author: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
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Message-id: <1394473304-7190-2-git-send-email-dgilbert@redhat.com>
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Patchwork-id: 58073
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O-Subject: [RHEL-7.0 qemu-kvm PATCH v2 1/2] qemu_file: use fwrite() correctly
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Bugzilla: 1005103
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RH-Acked-by: Juan Quintela <quintela@redhat.com>
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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RH-Acked-by: Amit Shah <amit.shah@redhat.com>
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From: Juan Quintela <quintela@redhat.com>
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fwrite() returns the number of items written. But when there is one
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error, it can return a short write.
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In the particular bug that I was tracking, I did a migration to a
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read-only filesystem. And it was able to finish the migration
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correctly. fwrite() never returned a negative error code, nor zero,
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always 4096. (migration writes chunks of about 14000 bytes). And it
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was able to "complete" the migration with success (yes, reading the
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file was a bit more difficult).
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To add insult to injury, if your amount of memory was big enough (12GB
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on my case), it overwrote some important structure, and from them,
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malloc failed. This check makes the problem go away.
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Markus Armbruster <armbru@redhat.com>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit aded6539d983280212e08d09f14157b1cb4d58cc)
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Conflicts:
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qemu-file.c
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Code still in savevm.c
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---
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savevm.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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savevm.c | 9 ++++++++-
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1 files changed, 8 insertions(+), 1 deletions(-)
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diff --git a/savevm.c b/savevm.c
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index bd37959..94121a2 100644
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--- a/savevm.c
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+++ b/savevm.c
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@@ -211,7 +211,14 @@ static int stdio_get_fd(void *opaque)
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static int stdio_put_buffer(void *opaque, const uint8_t *buf, int64_t pos, int size)
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{
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QEMUFileStdio *s = opaque;
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- return fwrite(buf, 1, size, s->stdio_file);
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+ int res;
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+
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+ res = fwrite(buf, 1, size, s->stdio_file);
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+
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+ if (res != size) {
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+ return -EIO; /* fake errno value */
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+ }
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+ return res;
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}
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static int stdio_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
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--
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1.7.1
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