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migration: Fix file migration with fdset

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When the "file:" migration support was added we missed the special
case in the qemu_open_old implementation that allows for a particular
file name format to be used to refer to a set of file descriptors that
have been previously provided to QEMU via the add-fd QMP command.

When using this fdset feature, we should not truncate the migration
file because being given an fd means that the management layer is in
control of the file and will likely already have some data written to
it. This is further indicated by the presence of the 'offset'
argument, which indicates the start of the region where QEMU is
allowed to write.

Fix the issue by replacing the O_TRUNC flag on open by an ftruncate
call, which will take the offset into consideration.

Fixes: 385f510df5 ("migration: file URI offset")
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
(cherry picked from commit 6d3279655a)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: context fixup in migration/file.c due to missing
 v8.2.0-1958-gb7b03eb614d0 "migration/multifd: Add outgoing QIOChannelFile support")
This commit is contained in:
Fabiano Rosas 2024-06-17 15:57:17 -03:00 committed by Michael Tokarev
parent 1229d60714
commit 5d9f2461b4
1 changed files with 9 additions and 2 deletions
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11
migration/file.c
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@ -46,12 +46,19 @@ void file_start_outgoing_migration(MigrationState *s,
trace_migration_file_outgoing(filename);
fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
0600, errp);
fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY, 0600, errp);
if (!fioc) {
return;
}
if (ftruncate(fioc->fd, offset)) {
error_setg_errno(errp, errno,
"failed to truncate migration file to offset %" PRIx64,
offset);
object_unref(OBJECT(fioc));
return;
}
ioc = QIO_CHANNEL(fioc);
if (offset && qio_channel_io_seek(ioc, offset, SEEK_SET, errp) < 0) {
return;