[v5,1/1] block: improve error handling in raw_open

Commit Message

Halil Pasic Oct. 11, 2016, 2:12 p.m. UTC

Make raw_open for POSIX more consistent in handling errors by setting
the error object also when qemu_open fails. The error object was set
generally set in case of errors, but I guess this case was overlooked.
Do the same for win32.

Signed-off-by: Halil Pasic <[e-mail]>
Reviewed-by: Sascha Silbe <[e-mail]>
Tested-by: Marc Hartmayer <[e-mail]> (POSIX only)

---

Stumbled upon this (POSIX) while testing VMs with too many SCSI disks in
respect to my nofile limit. When open hits the nofile limit while trying
to hotplug yet another SCSI disk via libvirt we end up with no adequate
error message (one stating too many files). Sadly this patch in not
sufficient to fix this problem because drive_new (/qemu/blockdev.c)
handles errors using error_report_err which is documented as not to be
used in QMP context.

The win32 part was not tested, and the sole reason I touched it is
to not introduce unnecessary divergence.

v4 -> v5:
* fix qemu-iotests by adding the filename to the message
v3 -> v4:
* rebased on current master
v2 -> v3:
* first save errno then error_setg_errno
v1 -> v2:
* fixed win32 by the correct error_setg_*
* use the original errno consequently
---
 block/raw-posix.c | 1 +
 block/raw-win32.c | 1 +
 2 files changed, 2 insertions(+)

Comments

Stefan Hajnoczi Oct. 14, 2016, 3:59 p.m. UTC | #1

On Tue, Oct 11, 2016 at 04:12:35PM +0200, Halil Pasic wrote:
> Make raw_open for POSIX more consistent in handling errors by setting
> the error object also when qemu_open fails. The error object was set
> generally set in case of errors, but I guess this case was overlooked.
> Do the same for win32.
> 
> Signed-off-by: Halil Pasic <[e-mail]>
> Reviewed-by: Sascha Silbe <[e-mail]>
> Tested-by: Marc Hartmayer <[e-mail]> (POSIX only)
> 
> ---
> 
> Stumbled upon this (POSIX) while testing VMs with too many SCSI disks in
> respect to my nofile limit. When open hits the nofile limit while trying
> to hotplug yet another SCSI disk via libvirt we end up with no adequate
> error message (one stating too many files). Sadly this patch in not
> sufficient to fix this problem because drive_new (/qemu/blockdev.c)
> handles errors using error_report_err which is documented as not to be
> used in QMP context.
> 
> The win32 part was not tested, and the sole reason I touched it is
> to not introduce unnecessary divergence.
> 
> v4 -> v5:
> * fix qemu-iotests by adding the filename to the message

This patch doesn't modify any iotests golden master files.  Does this
mean the iotests output is unchanged?

> v3 -> v4:
> * rebased on current master
> v2 -> v3:
> * first save errno then error_setg_errno
> v1 -> v2:
> * fixed win32 by the correct error_setg_*
> * use the original errno consequently
> ---
>  block/raw-posix.c | 1 +
>  block/raw-win32.c | 1 +
>  2 files changed, 2 insertions(+)

Reviewed-by: Stefan Hajnoczi <[e-mail]>

Halil Pasic Oct. 14, 2016, 4:27 p.m. UTC | #2

On 10/14/2016 05:59 PM, Stefan Hajnoczi wrote:
> On Tue, Oct 11, 2016 at 04:12:35PM +0200, Halil Pasic wrote:
>> > Make raw_open for POSIX more consistent in handling errors by setting
>> > the error object also when qemu_open fails. The error object was set
>> > generally set in case of errors, but I guess this case was overlooked.
>> > Do the same for win32.
>> > 
>> > Signed-off-by: Halil Pasic <[e-mail]>
>> > Reviewed-by: Sascha Silbe <[e-mail]>
>> > Tested-by: Marc Hartmayer <[e-mail]> (POSIX only)
>> > 
>> > ---
>> > 
>> > Stumbled upon this (POSIX) while testing VMs with too many SCSI disks in
>> > respect to my nofile limit. When open hits the nofile limit while trying
>> > to hotplug yet another SCSI disk via libvirt we end up with no adequate
>> > error message (one stating too many files). Sadly this patch in not
>> > sufficient to fix this problem because drive_new (/qemu/blockdev.c)
>> > handles errors using error_report_err which is documented as not to be
>> > used in QMP context.
>> > 
>> > The win32 part was not tested, and the sole reason I touched it is
>> > to not introduce unnecessary divergence.
>> > 
>> > v4 -> v5:
>> > * fix qemu-iotests by adding the filename to the message
> This patch doesn't modify any iotests golden master files.  Does this
> mean the iotests output is unchanged?
> 

Exactly. Instead of modifying the golden masters I choose to modify
the message generated by me and make it more verbose by appending
the filename in question.

Thanks for the review!

Halil

Kevin Wolf Oct. 17, 2016, 10:19 a.m. UTC | #3

Am 14.10.2016 um 17:59 hat Stefan Hajnoczi geschrieben:
> On Tue, Oct 11, 2016 at 04:12:35PM +0200, Halil Pasic wrote:
> > Make raw_open for POSIX more consistent in handling errors by setting
> > the error object also when qemu_open fails. The error object was set
> > generally set in case of errors, but I guess this case was overlooked.
> > Do the same for win32.
> > 
> > Signed-off-by: Halil Pasic <[e-mail]>
> > Reviewed-by: Sascha Silbe <[e-mail]>
> > Tested-by: Marc Hartmayer <[e-mail]> (POSIX only)
> > 
> > ---
> > 
> > Stumbled upon this (POSIX) while testing VMs with too many SCSI disks in
> > respect to my nofile limit. When open hits the nofile limit while trying
> > to hotplug yet another SCSI disk via libvirt we end up with no adequate
> > error message (one stating too many files). Sadly this patch in not
> > sufficient to fix this problem because drive_new (/qemu/blockdev.c)
> > handles errors using error_report_err which is documented as not to be
> > used in QMP context.
> > 
> > The win32 part was not tested, and the sole reason I touched it is
> > to not introduce unnecessary divergence.
> > 
> > v4 -> v5:
> > * fix qemu-iotests by adding the filename to the message
> 
> This patch doesn't modify any iotests golden master files.  Does this
> mean the iotests output is unchanged?
> 
> > v3 -> v4:
> > * rebased on current master
> > v2 -> v3:
> > * first save errno then error_setg_errno
> > v1 -> v2:
> > * fixed win32 by the correct error_setg_*
> > * use the original errno consequently
> > ---
> >  block/raw-posix.c | 1 +
> >  block/raw-win32.c | 1 +
> >  2 files changed, 2 insertions(+)
> 
> Reviewed-by: Stefan Hajnoczi <[e-mail]>

Thanks, applied to the block branch.

Kevin

Patch

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 166e9d1..f481e57 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -443,6 +443,7 @@  static int raw_open_common(BlockDriverState *bs, QDict *options,
     fd = qemu_open(filename, s->open_flags, 0644);
     if (fd < 0) {
         ret = -errno;
+        error_setg_errno(errp, errno, "Could not open '%s'", filename);
         if (ret == -EROFS) {
             ret = -EACCES;
         }
diff --git a/block/raw-win32.c b/block/raw-win32.c
index 734bb10..800fabd 100644
--- a/block/raw-win32.c
+++ b/block/raw-win32.c
@@ -373,6 +373,7 @@  static int raw_open(BlockDriverState *bs, QDict *options, int flags,
     if (s->hfile == INVALID_HANDLE_VALUE) {
         int err = GetLastError();
 
+        error_setg_win32(errp, err, "Could not open '%s'", filename);
         if (err == ERROR_ACCESS_DENIED) {
             ret = -EACCES;
         } else {