Re: [Qemu-devel] [PATCH] migration: Add error_desc for file channel errors

[Yury Kotov]

Hi, I'm a bit worried that this patch might have been forgotten.
Is it queued? Thanks!

14.06.2019, 19:56, "Dr. David Alan Gilbert" <address@hidden>:
> * Yury Kotov (address@hidden) wrote:
>>  Currently, there is no information about error if outgoing migration was 
>> failed
>>  because of file channel errors.
>>  Example (QMP session):
>>  -> { "execute": "migrate", "arguments": { "uri": "exec:head -c 1" }}
>>  <- { "return": {} }
>>  ...
>>  -> { "execute": "query-migrate" }
>>  <- { "return": { "status": "failed" }} // There is not error's description
>>
>>  And even in the QEMU's output there is nothing.
>>
>>  This patch
>>  1) Adds errp for the most of QEMUFileOps
>>  2) Adds qemu_file_get_error_obj/qemu_file_set_error_obj
>>  3) And finally using of qemu_file_get_error_obj in migration.c
>>
>>  And now, the status for the mentioned fail will be:
>>  -> { "execute": "query-migrate" }
>>  <- { "return": { "status": "failed",
>>                   "error-desc": "Unable to write to command: Broken pipe" }}
>>
>>  Signed-off-by: Yury Kotov <address@hidden>
>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
>
>>  ---
>>   migration/migration.c | 10 ++++--
>>   migration/qemu-file-channel.c | 30 +++++++++--------
>>   migration/qemu-file.c | 63 ++++++++++++++++++++++++++++-------
>>   migration/qemu-file.h | 15 ++++++---
>>   migration/savevm.c | 6 ++--
>>   5 files changed, 88 insertions(+), 36 deletions(-)
>>
>>  diff --git a/migration/migration.c b/migration/migration.c
>>  index 609e0df5d0..7bcdc4613b 100644
>>  --- a/migration/migration.c
>>  +++ b/migration/migration.c
>>  @@ -2949,6 +2949,7 @@ static MigThrError 
>> migration_detect_error(MigrationState *s)
>>   {
>>       int ret;
>>       int state = s->state;
>>  + Error *local_error = NULL;
>>
>>       if (state == MIGRATION_STATUS_CANCELLING ||
>>           state == MIGRATION_STATUS_CANCELLED) {
>>  @@ -2957,13 +2958,18 @@ static MigThrError 
>> migration_detect_error(MigrationState *s)
>>       }
>>
>>       /* Try to detect any file errors */
>>  - ret = qemu_file_get_error(s->to_dst_file);
>>  -
>>  + ret = qemu_file_get_error_obj(s->to_dst_file, &local_error);
>>       if (!ret) {
>>           /* Everything is fine */
>>  + assert(!local_error);
>>           return MIG_THR_ERR_NONE;
>>       }
>>
>>  + if (local_error) {
>>  + migrate_set_error(s, local_error);
>>  + error_free(local_error);
>>  + }
>>  +
>>       if (state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret == -EIO) {
>>           /*
>>            * For postcopy, we allow the network to be down for a
>>  diff --git a/migration/qemu-file-channel.c b/migration/qemu-file-channel.c
>>  index 8e639eb496..c382ea2d78 100644
>>  --- a/migration/qemu-file-channel.c
>>  +++ b/migration/qemu-file-channel.c
>>  @@ -33,7 +33,8 @@
>>   static ssize_t channel_writev_buffer(void *opaque,
>>                                        struct iovec *iov,
>>                                        int iovcnt,
>>  - int64_t pos)
>>  + int64_t pos,
>>  + Error **errp)
>>   {
>>       QIOChannel *ioc = QIO_CHANNEL(opaque);
>>       ssize_t done = 0;
>>  @@ -47,7 +48,7 @@ static ssize_t channel_writev_buffer(void *opaque,
>>
>>       while (nlocal_iov > 0) {
>>           ssize_t len;
>>  - len = qio_channel_writev(ioc, local_iov, nlocal_iov, NULL);
>>  + len = qio_channel_writev(ioc, local_iov, nlocal_iov, errp);
>>           if (len == QIO_CHANNEL_ERR_BLOCK) {
>>               if (qemu_in_coroutine()) {
>>                   qio_channel_yield(ioc, G_IO_OUT);
>>  @@ -57,7 +58,6 @@ static ssize_t channel_writev_buffer(void *opaque,
>>               continue;
>>           }
>>           if (len < 0) {
>>  - /* XXX handle Error objects */
>>               done = -EIO;
>>               goto cleanup;
>>           }
>>  @@ -75,13 +75,14 @@ static ssize_t channel_writev_buffer(void *opaque,
>>   static ssize_t channel_get_buffer(void *opaque,
>>                                     uint8_t *buf,
>>                                     int64_t pos,
>>  - size_t size)
>>  + size_t size,
>>  + Error **errp)
>>   {
>>       QIOChannel *ioc = QIO_CHANNEL(opaque);
>>       ssize_t ret;
>>
>>       do {
>>  - ret = qio_channel_read(ioc, (char *)buf, size, NULL);
>>  + ret = qio_channel_read(ioc, (char *)buf, size, errp);
>>           if (ret < 0) {
>>               if (ret == QIO_CHANNEL_ERR_BLOCK) {
>>                   if (qemu_in_coroutine()) {
>>  @@ -90,7 +91,6 @@ static ssize_t channel_get_buffer(void *opaque,
>>                       qio_channel_wait(ioc, G_IO_IN);
>>                   }
>>               } else {
>>  - /* XXX handle Error * object */
>>                   return -EIO;
>>               }
>>           }
>>  @@ -100,18 +100,20 @@ static ssize_t channel_get_buffer(void *opaque,
>>   }
>>
>>  -static int channel_close(void *opaque)
>>  +static int channel_close(void *opaque, Error **errp)
>>   {
>>  + int ret;
>>       QIOChannel *ioc = QIO_CHANNEL(opaque);
>>  - qio_channel_close(ioc, NULL);
>>  + ret = qio_channel_close(ioc, errp);
>>       object_unref(OBJECT(ioc));
>>  - return 0;
>>  + return ret;
>>   }
>>
>>   static int channel_shutdown(void *opaque,
>>                               bool rd,
>>  - bool wr)
>>  + bool wr,
>>  + Error **errp)
>>   {
>>       QIOChannel *ioc = QIO_CHANNEL(opaque);
>>
>>  @@ -125,8 +127,7 @@ static int channel_shutdown(void *opaque,
>>           } else {
>>               mode = QIO_CHANNEL_SHUTDOWN_WRITE;
>>           }
>>  - if (qio_channel_shutdown(ioc, mode, NULL) < 0) {
>>  - /* XXX handler Error * object */
>>  + if (qio_channel_shutdown(ioc, mode, errp) < 0) {
>>               return -EIO;
>>           }
>>       }
>>  @@ -135,11 +136,12 @@ static int channel_shutdown(void *opaque,
>>
>>   static int channel_set_blocking(void *opaque,
>>  - bool enabled)
>>  + bool enabled,
>>  + Error **errp)
>>   {
>>       QIOChannel *ioc = QIO_CHANNEL(opaque);
>>
>>  - if (qio_channel_set_blocking(ioc, enabled, NULL) < 0) {
>>  + if (qio_channel_set_blocking(ioc, enabled, errp) < 0) {
>>           return -1;
>>       }
>>       return 0;
>>  diff --git a/migration/qemu-file.c b/migration/qemu-file.c
>>  index 977b9ae07c..c52160e08b 100644
>>  --- a/migration/qemu-file.c
>>  +++ b/migration/qemu-file.c
>>  @@ -29,6 +29,7 @@
>>   #include "migration.h"
>>   #include "qemu-file.h"
>>   #include "trace.h"
>>  +#include "qapi/error.h"
>>
>>   #define IO_BUF_SIZE 32768
>>   #define MAX_IOV_SIZE MIN(IOV_MAX, 64)
>>  @@ -52,6 +53,7 @@ struct QEMUFile {
>>       unsigned int iovcnt;
>>
>>       int last_error;
>>  + Error *last_error_obj;
>>   };
>>
>>   /*
>>  @@ -63,7 +65,7 @@ int qemu_file_shutdown(QEMUFile *f)
>>       if (!f->ops->shut_down) {
>>           return -ENOSYS;
>>       }
>>  - return f->ops->shut_down(f->opaque, true, true);
>>  + return f->ops->shut_down(f->opaque, true, true, NULL);
>>   }
>>
>>   /*
>>  @@ -108,24 +110,55 @@ void qemu_file_set_hooks(QEMUFile *f, const 
>> QEMUFileHooks *hooks)
>>   }
>>
>>   /*
>>  - * Get last error for stream f
>>  + * Get last error for stream f with optional Error*
>>    *
>>    * Return negative error value if there has been an error on previous
>>    * operations, return 0 if no error happened.
>>  + * Optional, it returns Error* in errp, but it may be NULL even if return 
>> value
>>  + * is not 0.
>>    *
>>    */
>>  -int qemu_file_get_error(QEMUFile *f)
>>  +int qemu_file_get_error_obj(QEMUFile *f, Error **errp)
>>   {
>>  + if (errp) {
>>  + *errp = f->last_error_obj ? error_copy(f->last_error_obj) : NULL;
>>  + }
>>       return f->last_error;
>>   }
>>
>>  -void qemu_file_set_error(QEMUFile *f, int ret)
>>  +/*
>>  + * Set the last error for stream f with optional Error*
>>  + */
>>  +void qemu_file_set_error_obj(QEMUFile *f, int ret, Error *err)
>>   {
>>  - if (f->last_error == 0) {
>>  + if (f->last_error == 0 && ret) {
>>           f->last_error = ret;
>>  + error_propagate(&f->last_error_obj, err);
>>  + } else if (err) {
>>  + error_report_err(err);
>>       }
>>   }
>>
>>  +/*
>>  + * Get last error for stream f
>>  + *
>>  + * Return negative error value if there has been an error on previous
>>  + * operations, return 0 if no error happened.
>>  + *
>>  + */
>>  +int qemu_file_get_error(QEMUFile *f)
>>  +{
>>  + return qemu_file_get_error_obj(f, NULL);
>>  +}
>>  +
>>  +/*
>>  + * Set the last error for stream f
>>  + */
>>  +void qemu_file_set_error(QEMUFile *f, int ret)
>>  +{
>>  + qemu_file_set_error_obj(f, ret, NULL);
>>  +}
>>  +
>>   bool qemu_file_is_writable(QEMUFile *f)
>>   {
>>       return f->ops->writev_buffer;
>>  @@ -177,6 +210,7 @@ void qemu_fflush(QEMUFile *f)
>>   {
>>       ssize_t ret = 0;
>>       ssize_t expect = 0;
>>  + Error *local_error = NULL;
>>
>>       if (!qemu_file_is_writable(f)) {
>>           return;
>>  @@ -184,7 +218,8 @@ void qemu_fflush(QEMUFile *f)
>>
>>       if (f->iovcnt > 0) {
>>           expect = iov_size(f->iov, f->iovcnt);
>>  - ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt, f->pos);
>>  + ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt, f->pos,
>>  + &local_error);
>>
>>           qemu_iovec_release_ram(f);
>>       }
>>  @@ -196,7 +231,7 @@ void qemu_fflush(QEMUFile *f)
>>        * data set we requested, so sanity check that.
>>        */
>>       if (ret != expect) {
>>  - qemu_file_set_error(f, ret < 0 ? ret : -EIO);
>>  + qemu_file_set_error_obj(f, ret < 0 ? ret : -EIO, local_error);
>>       }
>>       f->buf_index = 0;
>>       f->iovcnt = 0;
>>  @@ -284,6 +319,7 @@ static ssize_t qemu_fill_buffer(QEMUFile *f)
>>   {
>>       int len;
>>       int pending;
>>  + Error *local_error = NULL;
>>
>>       assert(!qemu_file_is_writable(f));
>>
>>  @@ -295,14 +331,16 @@ static ssize_t qemu_fill_buffer(QEMUFile *f)
>>       f->buf_size = pending;
>>
>>       len = f->ops->get_buffer(f->opaque, f->buf + pending, f->pos,
>>  - IO_BUF_SIZE - pending);
>>  + IO_BUF_SIZE - pending, &local_error);
>>       if (len > 0) {
>>           f->buf_size += len;
>>           f->pos += len;
>>       } else if (len == 0) {
>>  - qemu_file_set_error(f, -EIO);
>>  + qemu_file_set_error_obj(f, -EIO, local_error);
>>       } else if (len != -EAGAIN) {
>>  - qemu_file_set_error(f, len);
>>  + qemu_file_set_error_obj(f, len, local_error);
>>  + } else {
>>  + error_free(local_error);
>>       }
>>
>>       return len;
>>  @@ -328,7 +366,7 @@ int qemu_fclose(QEMUFile *f)
>>       ret = qemu_file_get_error(f);
>>
>>       if (f->ops->close) {
>>  - int ret2 = f->ops->close(f->opaque);
>>  + int ret2 = f->ops->close(f->opaque, NULL);
>>           if (ret >= 0) {
>>               ret = ret2;
>>           }
>>  @@ -339,6 +377,7 @@ int qemu_fclose(QEMUFile *f)
>>       if (f->last_error) {
>>           ret = f->last_error;
>>       }
>>  + error_free(f->last_error_obj);
>>       g_free(f);
>>       trace_qemu_file_fclose();
>>       return ret;
>>  @@ -784,6 +823,6 @@ void qemu_put_counted_string(QEMUFile *f, const char 
>> *str)
>>   void qemu_file_set_blocking(QEMUFile *f, bool block)
>>   {
>>       if (f->ops->set_blocking) {
>>  - f->ops->set_blocking(f->opaque, block);
>>  + f->ops->set_blocking(f->opaque, block, NULL);
>>       }
>>   }
>>  diff --git a/migration/qemu-file.h b/migration/qemu-file.h
>>  index 13baf896bd..eb886db65f 100644
>>  --- a/migration/qemu-file.h
>>  +++ b/migration/qemu-file.h
>>  @@ -32,7 +32,8 @@
>>    * bytes actually read should be returned.
>>    */
>>   typedef ssize_t (QEMUFileGetBufferFunc)(void *opaque, uint8_t *buf,
>>  - int64_t pos, size_t size);
>>  + int64_t pos, size_t size,
>>  + Error **errp);
>>
>>   /* Close a file
>>    *
>>  @@ -41,7 +42,7 @@ typedef ssize_t (QEMUFileGetBufferFunc)(void *opaque, 
>> uint8_t *buf,
>>    * The meaning of return value on success depends on the specific back-end 
>> being
>>    * used.
>>    */
>>  -typedef int (QEMUFileCloseFunc)(void *opaque);
>>  +typedef int (QEMUFileCloseFunc)(void *opaque, Error **errp);
>>
>>   /* Called to return the OS file descriptor associated to the QEMUFile.
>>    */
>>  @@ -49,14 +50,15 @@ typedef int (QEMUFileGetFD)(void *opaque);
>>
>>   /* Called to change the blocking mode of the file
>>    */
>>  -typedef int (QEMUFileSetBlocking)(void *opaque, bool enabled);
>>  +typedef int (QEMUFileSetBlocking)(void *opaque, bool enabled, Error 
>> **errp);
>>
>>   /*
>>    * This function writes an iovec to file. The handler must write all
>>    * of the data or return a negative errno value.
>>    */
>>   typedef ssize_t (QEMUFileWritevBufferFunc)(void *opaque, struct iovec *iov,
>>  - int iovcnt, int64_t pos);
>>  + int iovcnt, int64_t pos,
>>  + Error **errp);
>>
>>   /*
>>    * This function provides hooks around different
>>  @@ -97,7 +99,8 @@ typedef QEMUFile *(QEMURetPathFunc)(void *opaque);
>>    * Existing blocking reads/writes must be woken
>>    * Returns 0 on success, -err on error
>>    */
>>  -typedef int (QEMUFileShutdownFunc)(void *opaque, bool rd, bool wr);
>>  +typedef int (QEMUFileShutdownFunc)(void *opaque, bool rd, bool wr,
>>  + Error **errp);
>>
>>   typedef struct QEMUFileOps {
>>       QEMUFileGetBufferFunc *get_buffer;
>>  @@ -149,6 +152,8 @@ void qemu_update_position(QEMUFile *f, size_t size);
>>   void qemu_file_reset_rate_limit(QEMUFile *f);
>>   void qemu_file_set_rate_limit(QEMUFile *f, int64_t new_rate);
>>   int64_t qemu_file_get_rate_limit(QEMUFile *f);
>>  +int qemu_file_get_error_obj(QEMUFile *f, Error **errp);
>>  +void qemu_file_set_error_obj(QEMUFile *f, int ret, Error *err);
>>   void qemu_file_set_error(QEMUFile *f, int ret);
>>   int qemu_file_shutdown(QEMUFile *f);
>>   QEMUFile *qemu_file_get_return_path(QEMUFile *f);
>>  diff --git a/migration/savevm.c b/migration/savevm.c
>>  index 34bcad3807..a619af744d 100644
>>  --- a/migration/savevm.c
>>  +++ b/migration/savevm.c
>>  @@ -124,7 +124,7 @@ static struct mig_cmd_args {
>>   /* savevm/loadvm support */
>>
>>   static ssize_t block_writev_buffer(void *opaque, struct iovec *iov, int 
>> iovcnt,
>>  - int64_t pos)
>>  + int64_t pos, Error **errp)
>>   {
>>       int ret;
>>       QEMUIOVector qiov;
>>  @@ -139,12 +139,12 @@ static ssize_t block_writev_buffer(void *opaque, 
>> struct iovec *iov, int iovcnt,
>>   }
>>
>>   static ssize_t block_get_buffer(void *opaque, uint8_t *buf, int64_t pos,
>>  - size_t size)
>>  + size_t size, Error **errp)
>>   {
>>       return bdrv_load_vmstate(opaque, buf, pos, size);
>>   }
>>
>>  -static int bdrv_fclose(void *opaque)
>>  +static int bdrv_fclose(void *opaque, Error **errp)
>>   {
>>       return bdrv_flush(opaque);
>>   }
>>  --
>>  2.21.0
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK

Regards,
Yury