[PATCH v2 0/1] LUKS: Fix error message when underlying fs don't support large enough files

[PATCH v2 0/1] LUKS: Fix error message when underlying fs don't support large enough files

[Maxim Levitsky]

This is a repost of the same trivial patch I already, which fell through the cracks.
Could someone queue it up so I close the bugzilla I have for this?

V2: fixed usage of local_err

Best regards,
	Maxim Levitsky

Maxim Levitsky (1):
  block/crypto: better error message when creating too large files

 block/crypto.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

-- 
2.17.2

[PATCH v2 1/1] block/crypto: better error message when creating too large files

[Maxim Levitsky]

Currently if you attampt to create too large file with luks you
get the following error message:

Formatting 'test.luks', fmt=luks size=17592186044416 key-secret=sec0
qemu-img: test.luks: Could not resize file: File too large

While for raw format the error message is
qemu-img: test.img: The image size is too large for file format 'raw'


The reason for this is that qemu-img checks for errono of the failure,
and presents the later error when it is -EFBIG

However crypto generic code 'swallows' the errno and replaces it
with -EIO.

As an attempt to make it better, we can make luks driver,
detect -EFBIG and in this case present a better error message,
which is what this patch does

The new error message is:

qemu-img: error creating test.luks: The requested file size is too large

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1534898
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 block/crypto.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/block/crypto.c b/block/crypto.c
index d577f89659..f9f5dc11a7 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -104,18 +104,35 @@ static ssize_t block_crypto_init_func(QCryptoBlock *block,
                                       Error **errp)
 {
     struct BlockCryptoCreateData *data = opaque;
+    Error *local_err = NULL;
+    int ret;
 
     if (data->size > INT64_MAX || headerlen > INT64_MAX - data->size) {
-        error_setg(errp, "The requested file size is too large");
-        return -EFBIG;
+        ret = -EFBIG;
+        goto error;
     }
 
     /* User provided size should reflect amount of space made
      * available to the guest, so we must take account of that
      * which will be used by the crypto header
      */
-    return blk_truncate(data->blk, data->size + headerlen, false,
-                        data->prealloc, errp);
+    ret = blk_truncate(data->blk, data->size + headerlen, false,
+                        data->prealloc, &local_err);
+
+    if (ret >= 0) {
+        return ret;
+    }
+
+error:
+    if (ret == -EFBIG) {
+        /* Replace the error message with a better one */
+        error_free(local_err);
+        error_setg(errp, "The requested file size is too large");
+    } else {
+        error_propagate(errp, local_err);
+    }
+
+    return ret;
 }
 
 
-- 
2.17.2

Re: [PATCH v2 1/1] block/crypto: better error message when creating too large files

[Maxim Levitsky]

On Mon, 2020-04-20 at 12:29 +0300, Maxim Levitsky wrote:
> Currently if you attampt to create too large file with luks you
> get the following error message:
> 
> Formatting 'test.luks', fmt=luks size=17592186044416 key-secret=sec0
> qemu-img: test.luks: Could not resize file: File too large
> 
> While for raw format the error message is
> qemu-img: test.img: The image size is too large for file format 'raw'
> 
> 
> The reason for this is that qemu-img checks for errono of the failure,
> and presents the later error when it is -EFBIG
> 
> However crypto generic code 'swallows' the errno and replaces it
> with -EIO.
> 
> As an attempt to make it better, we can make luks driver,
> detect -EFBIG and in this case present a better error message,
> which is what this patch does
> 
> The new error message is:
> 
> qemu-img: error creating test.luks: The requested file size is too large
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1534898
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  block/crypto.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/block/crypto.c b/block/crypto.c
> index d577f89659..f9f5dc11a7 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -104,18 +104,35 @@ static ssize_t block_crypto_init_func(QCryptoBlock *block,
>                                        Error **errp)
>  {
>      struct BlockCryptoCreateData *data = opaque;
> +    Error *local_err = NULL;
> +    int ret;
>  
>      if (data->size > INT64_MAX || headerlen > INT64_MAX - data->size) {
> -        error_setg(errp, "The requested file size is too large");
> -        return -EFBIG;
> +        ret = -EFBIG;
> +        goto error;
>      }
>  
>      /* User provided size should reflect amount of space made
>       * available to the guest, so we must take account of that
>       * which will be used by the crypto header
>       */
> -    return blk_truncate(data->blk, data->size + headerlen, false,
> -                        data->prealloc, errp);
> +    ret = blk_truncate(data->blk, data->size + headerlen, false,
> +                        data->prealloc, &local_err);
> +
> +    if (ret >= 0) {
> +        return ret;
> +    }
> +
> +error:
> +    if (ret == -EFBIG) {
> +        /* Replace the error message with a better one */
> +        error_free(local_err);
> +        error_setg(errp, "The requested file size is too large");
> +    } else {
> +        error_propagate(errp, local_err);
> +    }
> +
> +    return ret;
>  }
>  
>  
Could someone pick that patch now that the freeze is over?
Best regards,
	Maxim Levitsky