[PATCH] btrfs: Return right extent when fiemap gives unaligned offset and len.

[PATCH] btrfs: Return right extent when fiemap gives unaligned offset and len.

[Qu Wenruo]

When page aligned start and len passed to extent_fiemap(), the result is
good, but when start and len is not aligned, e.g. start = 1 and len =
4095 is passed to extent_fiemap(), it returns no extent.

The problem is that start and len is all rounded down which causes the
problem. This patch will round down start and round up (start + len) to
return right extent.

Reported-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/extent_io.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a389820..1c70cff 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4213,8 +4213,8 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		return -ENOMEM;
 	path->leave_spinning = 1;
 
-	start = ALIGN(start, BTRFS_I(inode)->root->sectorsize);
-	len = ALIGN(len, BTRFS_I(inode)->root->sectorsize);
+	start = round_down(start, BTRFS_I(inode)->root->sectorsize);
+	len = round_up(max, BTRFS_I(inode)->root->sectorsize) - start;
 
 	/*
 	 * lookup the last file extent.  We're not using i_size here
-- 
2.0.1

Re: [PATCH] btrfs: Return right extent when fiemap gives unaligned offset and len.

[David Sterba]

On Fri, Jul 18, 2014 at 09:55:43AM +0800, Qu Wenruo wrote:
> When page aligned start and len passed to extent_fiemap(), the result is
> good, but when start and len is not aligned, e.g. start = 1 and len =
> 4095 is passed to extent_fiemap(), it returns no extent.
> 
> The problem is that start and len is all rounded down which causes the
> problem.

ALIGN rounds up, not down. So the wrong rounding will use incorrect start
(4096) and finds no extents if there's eg. only one [0,4095].

> This patch will round down start and round up (start + len) to
> return right extent.
> 
> Reported-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>

Reviewed-by: David Sterba <dsterba@suse.cz>

Re: [PATCH] btrfs: Return right extent when fiemap gives unaligned offset and len.

[Qu Wenruo]

-------- Original Message --------
Subject: Re: [PATCH] btrfs: Return right extent when fiemap gives 
unaligned offset and len.
From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: 2014年07月24日 20:17
> On Fri, Jul 18, 2014 at 09:55:43AM +0800, Qu Wenruo wrote:
>> When page aligned start and len passed to extent_fiemap(), the result is
>> good, but when start and len is not aligned, e.g. start = 1 and len =
>> 4095 is passed to extent_fiemap(), it returns no extent.
>>
>> The problem is that start and len is all rounded down which causes the
>> problem.
> ALIGN rounds up, not down. So the wrong rounding will use incorrect start
> (4096) and finds no extents if there's eg. only one [0,4095].
Sorry for the wrong description in patch.
Should I reword the patch and send a v2 patch?

Thanks,
Qu
>
>> This patch will round down start and round up (start + len) to
>> return right extent.
>>
>> Reported-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Reviewed-by: David Sterba <dsterba@suse.cz>

Re: [PATCH] btrfs: Return right extent when fiemap gives unaligned offset and len.

[David Sterba]

On Fri, Jul 25, 2014 at 09:29:05AM +0800, Qu Wenruo wrote:
> 
> -------- Original Message --------
> Subject: Re: [PATCH] btrfs: Return right extent when fiemap gives unaligned
> offset and len.
> From: David Sterba <dsterba@suse.cz>
> To: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Date: 2014年07月24日 20:17
> >On Fri, Jul 18, 2014 at 09:55:43AM +0800, Qu Wenruo wrote:
> >>When page aligned start and len passed to extent_fiemap(), the result is
> >>good, but when start and len is not aligned, e.g. start = 1 and len =
> >>4095 is passed to extent_fiemap(), it returns no extent.
> >>
> >>The problem is that start and len is all rounded down which causes the
> >>problem.
> >ALIGN rounds up, not down. So the wrong rounding will use incorrect start
> >(4096) and finds no extents if there's eg. only one [0,4095].
> Sorry for the wrong description in patch.
> Should I reword the patch and send a v2 patch?

You already did, but yes please.