[v4,10/25] block: Add bdrv_dirname()
diff mbox

Message ID 20170116204921.31578-3-mreitz@redhat.com
State New
Headers show

Commit Message

Max Reitz Jan. 16, 2017, 8:49 p.m. UTC
This function may be implemented by block drivers to derive a directory
name from a BDS. Concatenating this g_free()-able string with a relative
filename must result in a valid (not necessarily existing) filename, so
this is a function that should generally be not implemented by format
drivers, because this is protocol-specific.

If a BDS's driver does not implement this function, bdrv_dirname() will
fall through to the BDS's file if it exists. If it does not, the
exact_filename field will be used to generate a directory name.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 include/block/block.h     |  1 +
 include/block/block_int.h |  1 +
 block.c                   | 26 ++++++++++++++++++++++++++
 3 files changed, 28 insertions(+)

Comments

Eric Blake Jan. 16, 2017, 11:02 p.m. UTC | #1
On 01/16/2017 02:49 PM, Max Reitz wrote:
> This function may be implemented by block drivers to derive a directory
> name from a BDS. Concatenating this g_free()-able string with a relative
> filename must result in a valid (not necessarily existing) filename, so
> this is a function that should generally be not implemented by format
> drivers, because this is protocol-specific.
> 
> If a BDS's driver does not implement this function, bdrv_dirname() will
> fall through to the BDS's file if it exists. If it does not, the
> exact_filename field will be used to generate a directory name.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  include/block/block.h     |  1 +
>  include/block/block_int.h |  1 +
>  block.c                   | 26 ++++++++++++++++++++++++++
>  3 files changed, 28 insertions(+)

> +++ b/include/block/block_int.h
> @@ -130,6 +130,7 @@ struct BlockDriver {
>      int (*bdrv_make_empty)(BlockDriverState *bs);
>  
>      void (*bdrv_refresh_filename)(BlockDriverState *bs, QDict *options);
> +    char *(*bdrv_dirname)(BlockDriverState *bs, Error **errp);

I know we've been lousy at documentation in the past, but should we
start doing a better job of documenting the contract as we add new
callbacks, rather than just the commit messages?

Based on existing practice, though, I'm okay with:
Reviewed-by: Eric Blake <eblake@redhat.com>
Max Reitz Jan. 18, 2017, 1:33 p.m. UTC | #2
On 17.01.2017 00:02, Eric Blake wrote:
> On 01/16/2017 02:49 PM, Max Reitz wrote:
>> This function may be implemented by block drivers to derive a directory
>> name from a BDS. Concatenating this g_free()-able string with a relative
>> filename must result in a valid (not necessarily existing) filename, so
>> this is a function that should generally be not implemented by format
>> drivers, because this is protocol-specific.
>>
>> If a BDS's driver does not implement this function, bdrv_dirname() will
>> fall through to the BDS's file if it exists. If it does not, the
>> exact_filename field will be used to generate a directory name.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>  include/block/block.h     |  1 +
>>  include/block/block_int.h |  1 +
>>  block.c                   | 26 ++++++++++++++++++++++++++
>>  3 files changed, 28 insertions(+)
> 
>> +++ b/include/block/block_int.h
>> @@ -130,6 +130,7 @@ struct BlockDriver {
>>      int (*bdrv_make_empty)(BlockDriverState *bs);
>>  
>>      void (*bdrv_refresh_filename)(BlockDriverState *bs, QDict *options);
>> +    char *(*bdrv_dirname)(BlockDriverState *bs, Error **errp);
> 
> I know we've been lousy at documentation in the past, but should we
> start doing a better job of documenting the contract as we add new
> callbacks, rather than just the commit messages?

Good point, I'll add a comment.

> Based on existing practice, though, I'm okay with:
> Reviewed-by: Eric Blake <eblake@redhat.com>

Thanks for reviewing!

Max

Patch
diff mbox

diff --git a/include/block/block.h b/include/block/block.h
index eb41956bf1..7bcbd05338 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -439,6 +439,7 @@  char *bdrv_get_full_backing_filename(BlockDriverState *bs, Error **errp);
 char *bdrv_get_full_backing_filename_from_filename(const char *backed,
                                                    const char *backing,
                                                    Error **errp);
+char *bdrv_dirname(BlockDriverState *bs, Error **errp);
 
 int path_has_protocol(const char *path);
 int path_is_absolute(const char *path);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index c1f057ab47..fb916a7890 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -130,6 +130,7 @@  struct BlockDriver {
     int (*bdrv_make_empty)(BlockDriverState *bs);
 
     void (*bdrv_refresh_filename)(BlockDriverState *bs, QDict *options);
+    char *(*bdrv_dirname)(BlockDriverState *bs, Error **errp);
 
     /* aio */
     BlockAIOCB *(*bdrv_aio_readv)(BlockDriverState *bs,
diff --git a/block.c b/block.c
index 2735ec4bcc..e591e326c5 100644
--- a/block.c
+++ b/block.c
@@ -4083,6 +4083,32 @@  void bdrv_refresh_filename(BlockDriverState *bs)
     }
 }
 
+char *bdrv_dirname(BlockDriverState *bs, Error **errp)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (!drv) {
+        error_setg(errp, "Node '%s' is ejected", bs->node_name);
+        return NULL;
+    }
+
+    if (drv->bdrv_dirname) {
+        return drv->bdrv_dirname(bs, errp);
+    }
+
+    if (bs->file) {
+        return bdrv_dirname(bs->file->bs, errp);
+    }
+
+    if (bs->exact_filename[0] != '\0') {
+        return path_combine(bs->exact_filename, "");
+    }
+
+    error_setg(errp, "Cannot generate a base directory for %s nodes",
+               drv->format_name);
+    return NULL;
+}
+
 /*
  * Hot add/remove a BDS's child. So the user can take a child offline when
  * it is broken and take a new child online