[PATCH 1/2] ext4: Fix block zeroing when punching holes in indirect block files

[PATCH 1/2] ext4: Fix block zeroing when punching holes in indirect block files

[Jan Kara]

free_holes_block() passed local variable as a block pointer
to ext4_clear_blocks(). Thus ext4_clear_blocks() zeroed out this local
variable instead of proper place in inode / indirect block. We later
zero out proper place in inode / indirect block but don't dirty the
inode / buffer again which can lead to subtle issues (some changes e.g.
to inode can be lost).

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/indirect.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 8a57e9fcd1b9..9d381707a6fc 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -1329,8 +1329,8 @@ static int free_hole_blocks(handle_t *handle, struct inode *inode,
 		if (level == 0 ||
 		    (bh && all_zeroes((__le32 *)bh->b_data,
 				      (__le32 *)bh->b_data + addr_per_block))) {
-			ext4_free_data(handle, inode, parent_bh, &blk, &blk+1);
-			*i_data = 0;
+			ext4_free_data(handle, inode, parent_bh,
+				       i_data, i_data + 1);
 		}
 		brelse(bh);
 		bh = NULL;
-- 
1.8.1.4

[PATCH 2/2] ext4: Fix hole punching for files with indirect blocks

[Jan Kara]

Hole punching code for files with indirect blocks wrongly computed
number of blocks which need to be cleared when traversing the indirect
block tree. That could result in punching more blocks than actually
requested and thus effectively cause a data loss. For example:

fallocate -n -p 10240000 4096

will punch the range 10240000 - 12632064 instead of the range 1024000 -
10244096. Fix the calculation.

CC: stable@vger.kernel.org
Fixes: 8bad6fc813a3a5300f51369c39d315679fd88c72
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/indirect.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 9d381707a6fc..771949c82715 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -1310,16 +1310,24 @@ static int free_hole_blocks(handle_t *handle, struct inode *inode,
 		blk = *i_data;
 		if (level > 0) {
 			ext4_lblk_t first2;
+			ext4_lblk_t count2;
+
 			bh = sb_bread(inode->i_sb, le32_to_cpu(blk));
 			if (!bh) {
 				EXT4_ERROR_INODE_BLOCK(inode, le32_to_cpu(blk),
 						       "Read failure");
 				return -EIO;
 			}
-			first2 = (first > offset) ? first - offset : 0;
+			if (first > offset) {
+				first2 = first - offset;
+				count2 = count;
+			} else {
+				first2 = 0;
+				count2 = count - (offset - first);
+			}
 			ret = free_hole_blocks(handle, inode, bh,
 					       (__le32 *)bh->b_data, level - 1,
-					       first2, count - offset,
+					       first2, count2,
 					       inode->i_sb->s_blocksize >> 2);
 			if (ret) {
 				brelse(bh);
-- 
1.8.1.4

Re: [PATCH 1/2] ext4: Fix block zeroing when punching holes in indirect block files

[Lukáš Czerner]

On Wed, 18 Jun 2014, Jan Kara wrote:

> Date: Wed, 18 Jun 2014 21:33:03 +0200
> From: Jan Kara <jack@suse.cz>
> To: Ted Tso <tytso@mit.edu>
> Cc: linux-ext4@vger.kernel.org, Jan Kara <jack@suse.cz>
> Subject: [PATCH 1/2] ext4: Fix block zeroing when punching holes in indirect
>     block files
> 
> free_holes_block() passed local variable as a block pointer
> to ext4_clear_blocks(). Thus ext4_clear_blocks() zeroed out this local
> variable instead of proper place in inode / indirect block. We later
> zero out proper place in inode / indirect block but don't dirty the
> inode / buffer again which can lead to subtle issues (some changes e.g.
> to inode can be lost).

Please see my patch

[PATCH] ext4: Fix punch hole on files with indirect mapping

which fixes those issues in a different way while also make this
operation faster.

Thanks!
-Lukas

> 
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/ext4/indirect.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 8a57e9fcd1b9..9d381707a6fc 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -1329,8 +1329,8 @@ static int free_hole_blocks(handle_t *handle, struct inode *inode,
>  		if (level == 0 ||
>  		    (bh && all_zeroes((__le32 *)bh->b_data,
>  				      (__le32 *)bh->b_data + addr_per_block))) {
> -			ext4_free_data(handle, inode, parent_bh, &blk, &blk+1);
> -			*i_data = 0;
> +			ext4_free_data(handle, inode, parent_bh,
> +				       i_data, i_data + 1);
>  		}
>  		brelse(bh);
>  		bh = NULL;
> 

[PATCH 1/2] ext4: Fix block zeroing when punching holes in indirect block files

[Jan Kara]

free_holes_block() passed local variable as a block pointer
to ext4_clear_blocks(). Thus ext4_clear_blocks() zeroed out this local
variable instead of proper place in inode / indirect block. We later
zero out proper place in inode / indirect block but don't dirty the
inode / buffer again which can lead to subtle issues (some changes e.g.
to inode can be lost).

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/indirect.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 8a57e9fcd1b9..9d381707a6fc 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -1329,8 +1329,8 @@ static int free_hole_blocks(handle_t *handle, struct inode *inode,
 		if (level == 0 ||
 		    (bh && all_zeroes((__le32 *)bh->b_data,
 				      (__le32 *)bh->b_data + addr_per_block))) {
-			ext4_free_data(handle, inode, parent_bh, &blk, &blk+1);
-			*i_data = 0;
+			ext4_free_data(handle, inode, parent_bh,
+				       i_data, i_data + 1);
 		}
 		brelse(bh);
 		bh = NULL;
-- 
1.8.1.4


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