* [PATCH] Btrfs-progs: fix btrfs-map-logical to only print extent mapping info
@ 2016-07-15 1:40 Liu Bo
2016-07-15 2:22 ` Qu Wenruo
0 siblings, 1 reply; 3+ messages in thread
From: Liu Bo @ 2016-07-15 1:40 UTC (permalink / raw)
To: linux-btrfs; +Cc: David Sterba
I have a valid btrfs image which contains,
...
item 10 key (1103101952 BLOCK_GROUP_ITEM 1288372224) itemoff 15947 itemsize 24
block group used 655360 chunk_objectid 256 flags DATA|RAID5
item 11 key (1103364096 EXTENT_ITEM 131072) itemoff 15894 itemsize 53
extent refs 1 gen 11 flags DATA
extent data backref root 5 objectid 258 offset 0 count 1
item 12 key (1103888384 EXTENT_ITEM 262144) itemoff 15841 itemsize 53
extent refs 1 gen 15 flags DATA
extent data backref root 1 objectid 256 offset 0 count 1
item 13 key (1104281600 EXTENT_ITEM 262144) itemoff 15788 itemsize 53
extent refs 1 gen 15 flags DATA
extent data backref root 1 objectid 257 offset 0 count 1
...
The extent [1103364096, 131072) has length 131072, but if we run
"btrfs-map-logical -l 1103364096 -b $((65536 * 3)) /dev/sda"
it will return mapping info 's of non-existing extents.
It's because it assumes that extents's are contiguous on logical address,
when it's not true, after one loop (cur_logical += cur_len) and mapping
the next extent, we can get an extent that is out of our search range and
we end up with a negative @real_len and printing all mapping infos till
the disk end.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
btrfs-map-logical.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/btrfs-map-logical.c b/btrfs-map-logical.c
index fd0286d..f421a50 100644
--- a/btrfs-map-logical.c
+++ b/btrfs-map-logical.c
@@ -329,6 +329,11 @@ int main(int argc, char **argv)
goto out_close_fd;
if (ret > 0)
break;
+ /* check again if there is overlap. */
+ if (cur_logical + cur_len < logical ||
+ cur_logical >= logical + bytes)
+ break;
+
real_logical = max(logical, cur_logical);
real_len = min(logical + bytes, cur_logical + cur_len) -
real_logical;
--
2.5.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] Btrfs-progs: fix btrfs-map-logical to only print extent mapping info
2016-07-15 1:40 [PATCH] Btrfs-progs: fix btrfs-map-logical to only print extent mapping info Liu Bo
@ 2016-07-15 2:22 ` Qu Wenruo
2016-07-15 9:45 ` David Sterba
0 siblings, 1 reply; 3+ messages in thread
From: Qu Wenruo @ 2016-07-15 2:22 UTC (permalink / raw)
To: Liu Bo, linux-btrfs; +Cc: David Sterba
At 07/15/2016 09:40 AM, Liu Bo wrote:
> I have a valid btrfs image which contains,
> ...
> item 10 key (1103101952 BLOCK_GROUP_ITEM 1288372224) itemoff 15947 itemsize 24
> block group used 655360 chunk_objectid 256 flags DATA|RAID5
> item 11 key (1103364096 EXTENT_ITEM 131072) itemoff 15894 itemsize 53
> extent refs 1 gen 11 flags DATA
> extent data backref root 5 objectid 258 offset 0 count 1
> item 12 key (1103888384 EXTENT_ITEM 262144) itemoff 15841 itemsize 53
> extent refs 1 gen 15 flags DATA
> extent data backref root 1 objectid 256 offset 0 count 1
> item 13 key (1104281600 EXTENT_ITEM 262144) itemoff 15788 itemsize 53
> extent refs 1 gen 15 flags DATA
> extent data backref root 1 objectid 257 offset 0 count 1
> ...
>
> The extent [1103364096, 131072) has length 131072, but if we run
>
> "btrfs-map-logical -l 1103364096 -b $((65536 * 3)) /dev/sda"
>
> it will return mapping info 's of non-existing extents.
>
> It's because it assumes that extents's are contiguous on logical address,
> when it's not true, after one loop (cur_logical += cur_len) and mapping
> the next extent, we can get an extent that is out of our search range and
> we end up with a negative @real_len and printing all mapping infos till
> the disk end.
>
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Yes, the assumption of all extents are contiguous is quite wrong.
So your check is needed.
Thanks,
Qu
> ---
> btrfs-map-logical.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/btrfs-map-logical.c b/btrfs-map-logical.c
> index fd0286d..f421a50 100644
> --- a/btrfs-map-logical.c
> +++ b/btrfs-map-logical.c
> @@ -329,6 +329,11 @@ int main(int argc, char **argv)
> goto out_close_fd;
> if (ret > 0)
> break;
> + /* check again if there is overlap. */
> + if (cur_logical + cur_len < logical ||
> + cur_logical >= logical + bytes)
> + break;
> +
> real_logical = max(logical, cur_logical);
> real_len = min(logical + bytes, cur_logical + cur_len) -
> real_logical;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Btrfs-progs: fix btrfs-map-logical to only print extent mapping info
2016-07-15 2:22 ` Qu Wenruo
@ 2016-07-15 9:45 ` David Sterba
0 siblings, 0 replies; 3+ messages in thread
From: David Sterba @ 2016-07-15 9:45 UTC (permalink / raw)
To: Qu Wenruo; +Cc: Liu Bo, linux-btrfs, David Sterba
On Fri, Jul 15, 2016 at 10:22:52AM +0800, Qu Wenruo wrote:
>
>
> At 07/15/2016 09:40 AM, Liu Bo wrote:
> > I have a valid btrfs image which contains,
> > ...
> > item 10 key (1103101952 BLOCK_GROUP_ITEM 1288372224) itemoff 15947 itemsize 24
> > block group used 655360 chunk_objectid 256 flags DATA|RAID5
> > item 11 key (1103364096 EXTENT_ITEM 131072) itemoff 15894 itemsize 53
> > extent refs 1 gen 11 flags DATA
> > extent data backref root 5 objectid 258 offset 0 count 1
> > item 12 key (1103888384 EXTENT_ITEM 262144) itemoff 15841 itemsize 53
> > extent refs 1 gen 15 flags DATA
> > extent data backref root 1 objectid 256 offset 0 count 1
> > item 13 key (1104281600 EXTENT_ITEM 262144) itemoff 15788 itemsize 53
> > extent refs 1 gen 15 flags DATA
> > extent data backref root 1 objectid 257 offset 0 count 1
> > ...
> >
> > The extent [1103364096, 131072) has length 131072, but if we run
> >
> > "btrfs-map-logical -l 1103364096 -b $((65536 * 3)) /dev/sda"
> >
> > it will return mapping info 's of non-existing extents.
> >
> > It's because it assumes that extents's are contiguous on logical address,
> > when it's not true, after one loop (cur_logical += cur_len) and mapping
> > the next extent, we can get an extent that is out of our search range and
> > we end up with a negative @real_len and printing all mapping infos till
> > the disk end.
> >
> > Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
>
> Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Applied, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-07-15 1:40 [PATCH] Btrfs-progs: fix btrfs-map-logical to only print extent mapping info Liu Bo
2016-07-15 2:22 ` Qu Wenruo
2016-07-15 9:45 ` David Sterba
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