[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-block] [Qemu-devel] [PATCH 2/3] block/ssh: Make ssh_grow_file(

From: Eric Blake
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH 2/3] block/ssh: Make ssh_grow_file() blocking
Date: Wed, 14 Feb 2018 15:11:15 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0

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 <address@hidden>
  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 <address@hidden>

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

reply via email to

[Prev in Thread] Current Thread [Next in Thread]