[PATCH] xfs_repair: fix max block offset test

[PATCH] xfs_repair: fix max block offset test

[Eric Sandeen]

Eryu pointed out that in fstest xfs/071, we find corruption
reported at the end.  This test attempts to do IO at the
maximum possible offsets, and repair yields:

inode 1027 - extent offset too large - start 70, count 1, offset 2251799813685247
correcting nextents for inode 1027
bad data fork in inode 1027
would have cleared inode 1027

Repair is complaining that an extent *starts* at the maximum
block, but AFAICT, starting there is just fine, as long as
we also end there.  i.e. a one-block extent at the limit
is just fine.

So change the xfs_repair test to allow this situation.

Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

diff --git a/repair/dinode.c b/repair/dinode.c
index 38a6562..ca57a61 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -667,7 +667,9 @@ _("inode %" PRIu64 " - bad extent overflows - start %" PRIu64 ", "
 					irec.br_startoff);
 				goto done;
 		}
-		if (irec.br_startoff >= fs_max_file_offset)  {
+		/* Ensure this extent does not extend beyond the max offset */
+		if (irec.br_startoff + irec.br_blockcount - 1 >
+							fs_max_file_offset) {
 			do_warn(
 _("inode %" PRIu64 " - extent offset too large - start %" PRIu64 ", "
   "count %" PRIu64 ", offset %" PRIu64 "\n"),

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Re: [PATCH] xfs_repair: fix max block offset test

[Brian Foster]

On Thu, Dec 11, 2014 at 11:54:03AM -0600, Eric Sandeen wrote:
> Eryu pointed out that in fstest xfs/071, we find corruption
> reported at the end.  This test attempts to do IO at the
> maximum possible offsets, and repair yields:
> 
> inode 1027 - extent offset too large - start 70, count 1, offset 2251799813685247
> correcting nextents for inode 1027
> bad data fork in inode 1027
> would have cleared inode 1027
> 
> Repair is complaining that an extent *starts* at the maximum
> block, but AFAICT, starting there is just fine, as long as
> we also end there.  i.e. a one-block extent at the limit
> is just fine.
> 
> So change the xfs_repair test to allow this situation.
> 
> Reported-by: Eryu Guan <eguan@redhat.com>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---

Thought this looked familiar:

http://oss.sgi.com/archives/xfs/2014-09/msg00524.html

Either one is fine with me. If we use the fix below, I think we should
update the error message since it technically refers to the extent
offset and we slightly tweak the meaning of the failure.

Brian

> 
> diff --git a/repair/dinode.c b/repair/dinode.c
> index 38a6562..ca57a61 100644
> --- a/repair/dinode.c
> +++ b/repair/dinode.c
> @@ -667,7 +667,9 @@ _("inode %" PRIu64 " - bad extent overflows - start %" PRIu64 ", "
>  					irec.br_startoff);
>  				goto done;
>  		}
> -		if (irec.br_startoff >= fs_max_file_offset)  {
> +		/* Ensure this extent does not extend beyond the max offset */
> +		if (irec.br_startoff + irec.br_blockcount - 1 >
> +							fs_max_file_offset) {
>  			do_warn(
>  _("inode %" PRIu64 " - extent offset too large - start %" PRIu64 ", "
>    "count %" PRIu64 ", offset %" PRIu64 "\n"),
> 
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs

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Re: [PATCH] xfs_repair: fix max block offset test

[Eric Sandeen]

On 12/18/14 9:18 AM, Brian Foster wrote:

> Thought this looked familiar:
> 
> http://oss.sgi.com/archives/xfs/2014-09/msg00524.html

oh, whoops.  let me go read that, sorry!

-Eric

> Either one is fine with me. If we use the fix below, I think we should
> update the error message since it technically refers to the extent
> offset and we slightly tweak the meaning of the failure.
> 
> Brian
> 
>>
>> diff --git a/repair/dinode.c b/repair/dinode.c
>> index 38a6562..ca57a61 100644
>> --- a/repair/dinode.c
>> +++ b/repair/dinode.c
>> @@ -667,7 +667,9 @@ _("inode %" PRIu64 " - bad extent overflows - start %" PRIu64 ", "
>>  					irec.br_startoff);
>>  				goto done;
>>  		}
>> -		if (irec.br_startoff >= fs_max_file_offset)  {
>> +		/* Ensure this extent does not extend beyond the max offset */
>> +		if (irec.br_startoff + irec.br_blockcount - 1 >
>> +							fs_max_file_offset) {
>>  			do_warn(
>>  _("inode %" PRIu64 " - extent offset too large - start %" PRIu64 ", "
>>    "count %" PRIu64 ", offset %" PRIu64 "\n"),
>>
>> _______________________________________________
>> xfs mailing list
>> xfs@oss.sgi.com
>> http://oss.sgi.com/mailman/listinfo/xfs

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Re: [PATCH] xfs_repair: fix max block offset test

[Eric Sandeen]

On 12/18/14 9:18 AM, Brian Foster wrote:

hought this looked familiar:
> 
> http://oss.sgi.com/archives/xfs/2014-09/msg00524.html
> 
> Either one is fine with me. If we use the fix below, I think we should
> update the error message since it technically refers to the extent
> offset and we slightly tweak the meaning of the failure.
> 
> Brian

Ok, so here's what I wonder about with your patch.

+               if (irec.br_startoff > fs_max_file_offset)  {

What if the extent starting logical offset is *at* fs_max_file_offset
(which is sadly in blocks, not bytes, for extra confusion points),
but the extent is 1GB in length?

Isn't this a problem because we've now got files in the block which
are beyond fs_max_file_offset, and probably also beyond sb_maxbytes?

I'm not sure I follow why you feel the message needs to change with
my version:

+		/* Ensure this extent does not extend beyond the max offset */
+		if (irec.br_startoff + irec.br_blockcount - 1 >
+							fs_max_file_offset) {
                        do_warn(
_("inode %" PRIu64 " - extent offset too large - start %" PRIu64 ", "
  "count %" PRIu64 ", offset %" PRIu64 "\n"),
                                ino, irec.br_startblock, irec.br_blockcount,
                                irec.br_startoff);

If any (block) offset in the file is beyond the max, then we say the offset is
too large, and give it's physical block, its length, and its starting offset
(granted, the message is a bit *weird* - br_startblock really doesn't matter
here, but I don't think I've fundamentally changed the meaning of the test).

However, I've come to learn that you are almost always right about subtleties
like this, so perhaps you can explain again to me, using smaller words.  :)

-Eric

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[PATCH V2] xfs_repair: fix max block offset test

[Eric Sandeen]

Eryu pointed out that in fstest xfs/071, we find corruption
reported at the end.  This test attempts to do IO at the
maximum possible offsets, and repair yields:

inode 1027 - extent offset too large - start 70, count 1, offset 2251799813685247
correcting nextents for inode 1027
bad data fork in inode 1027
would have cleared inode 1027

Repair is complaining that an extent *starts* at the maximum
block, but AFAICT, starting there is just fine, as long as
we also end there.  i.e. a one-block extent at the limit
is just fine.

So change the xfs_repair test to allow this situation.

Also, the warning text is a bit unclear, mixing in the physical
block w/ the logical block... rearrange that a little to make
it obvious.

Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

V2: Update the warning text

diff --git a/repair/dinode.c b/repair/dinode.c
index 38a6562..59824ec 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -667,12 +667,14 @@ _("inode %" PRIu64 " - bad extent overflows - start %" PRIu64 ", "
 					irec.br_startoff);
 				goto done;
 		}
-		if (irec.br_startoff >= fs_max_file_offset)  {
+		/* Ensure this extent does not extend beyond the max offset */
+		if (irec.br_startoff + irec.br_blockcount - 1 >
+							fs_max_file_offset) {
 			do_warn(
-_("inode %" PRIu64 " - extent offset too large - start %" PRIu64 ", "
-  "count %" PRIu64 ", offset %" PRIu64 "\n"),
-				ino, irec.br_startblock, irec.br_blockcount,
-				irec.br_startoff);
+_("inode %" PRIu64 " - extent exceeds max offset - start %" PRIu64 ", "
+  "count %" PRIu64 ", physical block %" PRIu64 "\n"),
+				ino, irec.br_startoff, irec.br_blockcount,
+				irec.br_startblock);
 			goto done;
 		}
 


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Re: [PATCH] xfs_repair: fix max block offset test

[Brian Foster]

On Fri, Dec 19, 2014 at 12:54:22PM -0600, Eric Sandeen wrote:
> On 12/18/14 9:18 AM, Brian Foster wrote:
> 
> hought this looked familiar:
> > 
> > http://oss.sgi.com/archives/xfs/2014-09/msg00524.html
> > 
> > Either one is fine with me. If we use the fix below, I think we should
> > update the error message since it technically refers to the extent
> > offset and we slightly tweak the meaning of the failure.
> > 
> > Brian
> 
> Ok, so here's what I wonder about with your patch.
> 
> +               if (irec.br_startoff > fs_max_file_offset)  {
> 
> What if the extent starting logical offset is *at* fs_max_file_offset
> (which is sadly in blocks, not bytes, for extra confusion points),
> but the extent is 1GB in length?
> 
> Isn't this a problem because we've now got files in the block which
> are beyond fs_max_file_offset, and probably also beyond sb_maxbytes?
> 

Yeah... at the time I simply viewed this as outside the scope of this
particular check due to the logic and wording. It makes sense to widen
the logic to catch anything that starts before yet extends past max
offset, assuming we aren't actually checking that anywhere else.

> I'm not sure I follow why you feel the message needs to change with
> my version:
> 
> +		/* Ensure this extent does not extend beyond the max offset */
> +		if (irec.br_startoff + irec.br_blockcount - 1 >
> +							fs_max_file_offset) {
>                         do_warn(
> _("inode %" PRIu64 " - extent offset too large - start %" PRIu64 ", "
>   "count %" PRIu64 ", offset %" PRIu64 "\n"),
>                                 ino, irec.br_startblock, irec.br_blockcount,
>                                 irec.br_startoff);
> 
> If any (block) offset in the file is beyond the max, then we say the offset is
> too large, and give it's physical block, its length, and its starting offset
> (granted, the message is a bit *weird* - br_startblock really doesn't matter
> here, but I don't think I've fundamentally changed the meaning of the test).

As discussed on irc, I read "extent offset" as the offset of the extent
in the file, so it seemed a bit confusing if br_startoff isn't
necessarily the problem.

Brian

> 
> However, I've come to learn that you are almost always right about subtleties
> like this, so perhaps you can explain again to me, using smaller words.  :)
> 
> -Eric
> 
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs

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Re: [PATCH V2] xfs_repair: fix max block offset test

[Brian Foster]

On Fri, Dec 19, 2014 at 01:58:26PM -0600, Eric Sandeen wrote:
> Eryu pointed out that in fstest xfs/071, we find corruption
> reported at the end.  This test attempts to do IO at the
> maximum possible offsets, and repair yields:
> 
> inode 1027 - extent offset too large - start 70, count 1, offset 2251799813685247
> correcting nextents for inode 1027
> bad data fork in inode 1027
> would have cleared inode 1027
> 
> Repair is complaining that an extent *starts* at the maximum
> block, but AFAICT, starting there is just fine, as long as
> we also end there.  i.e. a one-block extent at the limit
> is just fine.
> 
> So change the xfs_repair test to allow this situation.
> 
> Also, the warning text is a bit unclear, mixing in the physical
> block w/ the logical block... rearrange that a little to make
> it obvious.
> 
> Reported-by: Eryu Guan <eguan@redhat.com>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---

Looks good to me. Thanks for the fixup. :)

Reviewed-by: Brian Foster <bfoster@redhat.com>

> 
> V2: Update the warning text
> 
> diff --git a/repair/dinode.c b/repair/dinode.c
> index 38a6562..59824ec 100644
> --- a/repair/dinode.c
> +++ b/repair/dinode.c
> @@ -667,12 +667,14 @@ _("inode %" PRIu64 " - bad extent overflows - start %" PRIu64 ", "
>  					irec.br_startoff);
>  				goto done;
>  		}
> -		if (irec.br_startoff >= fs_max_file_offset)  {
> +		/* Ensure this extent does not extend beyond the max offset */
> +		if (irec.br_startoff + irec.br_blockcount - 1 >
> +							fs_max_file_offset) {
>  			do_warn(
> -_("inode %" PRIu64 " - extent offset too large - start %" PRIu64 ", "
> -  "count %" PRIu64 ", offset %" PRIu64 "\n"),
> -				ino, irec.br_startblock, irec.br_blockcount,
> -				irec.br_startoff);
> +_("inode %" PRIu64 " - extent exceeds max offset - start %" PRIu64 ", "
> +  "count %" PRIu64 ", physical block %" PRIu64 "\n"),
> +				ino, irec.br_startoff, irec.br_blockcount,
> +				irec.br_startblock);
>  			goto done;
>  		}
>  
> 
> 
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs

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