From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50458) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1em4Kn-0007ud-Nk for qemu-devel@nongnu.org; Wed, 14 Feb 2018 16:11:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1em4Km-0008Hi-SX for qemu-devel@nongnu.org; Wed, 14 Feb 2018 16:11:21 -0500 References: <20180214204915.7980-1-mreitz@redhat.com> <20180214204915.7980-3-mreitz@redhat.com> From: Eric Blake Message-ID: Date: Wed, 14 Feb 2018 15:11:15 -0600 MIME-Version: 1.0 In-Reply-To: <20180214204915.7980-3-mreitz@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/3] block/ssh: Make ssh_grow_file() blocking List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz , qemu-block@nongnu.org Cc: Kevin Wolf , "Richard W . M . Jones" , Jeff Cody , qemu-devel@nongnu.org On 02/14/2018 02:49 PM, Max Reitz wrote: > At runtime (that is, during a future ssh_truncate()), the SSH session is > non-blocking. However, ssh_truncate() (or rather, bdrv_truncate() in > general) is not a coroutine, so this resize operation needs to block. > > For ssh_create(), that is fine, too; the session is never set to > non-blocking anyway. > > Signed-off-by: Max Reitz > --- > block/ssh.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/block/ssh.c b/block/ssh.c > index 964e55f7fe..ff8576f21e 100644 > --- a/block/ssh.c > +++ b/block/ssh.c > @@ -803,17 +803,24 @@ static int ssh_file_open(BlockDriverState *bs, QDict *options, int bdrv_flags, > return ret; > } > > +/* Note: This is a blocking operation */ > static int ssh_grow_file(BDRVSSHState *s, int64_t offset, Error **errp) > { > ssize_t ret; > char c[1] = { '\0' }; > + int was_blocking = libssh2_session_get_blocking(s->session); > > /* offset must be strictly greater than the current size so we do > * not overwrite anything */ > assert(offset > 0 && offset > s->attrs.filesize); > > + libssh2_session_set_blocking(s->session, 1); > + > libssh2_sftp_seek64(s->sftp_handle, offset - 1); > ret = libssh2_sftp_write(s->sftp_handle, c, 1); > + > + libssh2_session_set_blocking(s->session, was_blocking); Is it worth skipping the two libssh2_session_set_blocking() calls if was_blocking is 1? But that's a micro-optimization that probably won't be noticeable, so I'm also fine with unconditional. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org