From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v2] libxl: Reset toolstack_save file position in libxl Date: Mon, 19 May 2014 23:07:55 +0100 Message-ID: <537A80BB.6010609@citrix.com> References: <1400524597-6090-1-git-send-email-andryuk@aero.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1400524597-6090-1-git-send-email-andryuk@aero.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jason Andryuk , xen-devel@lists.xen.org Cc: Ian Jackson , Ian Campbell , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On 19/05/2014 19:36, Jason Andryuk wrote: > toolstack_save data is written to a temporary file in libxl and read > back in libxl-save-helper. The file position must be reset prior to > reading the file, which is done in libxl-save-helper with lseek. > > lseek is unsupported for pipes and sockets, so a wrapper passing such an > fd to libxl-save-helper fails the lseek. Moving the lseek to libxl > avoids the error, allowing the save to continue. > > Signed-off-by: Jason Andryuk > Reviewed-by: Andrew Cooper Ian: As noted previously, this should be a backport candidate. > --- > v2: > Use single line comment > --- > tools/libxl/libxl_save_callout.c | 4 ++++ > tools/libxl/libxl_save_helper.c | 5 ++--- > 2 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/tools/libxl/libxl_save_callout.c b/tools/libxl/libxl_save_callout.c > index 6e45b2f..1bfedfb 100644 > --- a/tools/libxl/libxl_save_callout.c > +++ b/tools/libxl/libxl_save_callout.c > @@ -105,6 +105,10 @@ void libxl__xc_domain_save(libxl__egc *egc, libxl__domain_suspend_state *dss, > toolstack_data_buf, toolstack_data_len, > "toolstack data tmpfile", 0); > if (r) { rc = ERROR_FAIL; goto out; } > + > + /* file position must be reset before passing to libxl-save-helper. */ > + r = lseek(toolstack_data_fd, 0, SEEK_SET); > + if (r) { rc = ERROR_FAIL; goto out; } > } > > const unsigned long argnums[] = { > diff --git a/tools/libxl/libxl_save_helper.c b/tools/libxl/libxl_save_helper.c > index 880565e..20ca13e 100644 > --- a/tools/libxl/libxl_save_helper.c > +++ b/tools/libxl/libxl_save_helper.c > @@ -169,10 +169,9 @@ static uint32_t toolstack_save_len; > static int toolstack_save_cb(uint32_t domid, uint8_t **buf, > uint32_t *len, void *data) > { > - assert(toolstack_save_fd > 0); > + int r; > > - int r = lseek(toolstack_save_fd, 0, SEEK_SET); > - if (r) fail(errno,"rewind toolstack data tmpfile"); > + assert(toolstack_save_fd > 0); > > *buf = xmalloc(toolstack_save_len); > r = read_exactly(toolstack_save_fd, *buf, toolstack_save_len);