Re: [PATCH 3/4]ext4: Return exchanged blocks count to user space in failure

[Akira Fujita <a-fujita@rs.jp.nec.com>]

Hi Peng,
Peng Tao wrote:
>>> After applying the two patches, I run my test case with first.img as the orig file (and middle.img or
>>> last.img as donor file). My kernel panics and I find following message in /var/log/messages after reboot:
>> I could not reproduce this panic.
>> Would you tell me about your test environment (1-5)?
>>
>> 1. What is your kernel version? (2.6.31-rc2 + ext4 patch queue + my patch?)
> Only 2.6.31-rc2 from linus tree + your two patches. I didn't apply ext4 patch queue.
>> 2. What FS mount options are enabled?
> rw,noatime,relatime,commit=360
>> 3. What options are enabled to create ext4?
>  [bergwolf@~]$sudo tune2fs -l /dev/sda9
> tune2fs 1.41.9 (22-Aug-2009)
> Filesystem volume name:   <none>
> Last mounted on:          /other
> Filesystem UUID:          90548cb8-5748-4b18-bbe9-e7254439cb82
> Filesystem magic number:  0xEF53
> Filesystem revision #:    1 (dynamic)
> Filesystem features:      has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
> Filesystem flags:         signed_directory_hash 
> Default mount options:    (none)
> Filesystem state:         clean
> Errors behavior:          Continue
> Filesystem OS type:       Linux
> Inode count:              125184
> Block count:              500015
> Reserved block count:     25000
> Free blocks:              299959
> Free inodes:              125162
> First block:              0
> Block size:               4096
> Fragment size:            4096
> Reserved GDT blocks:      122
> Blocks per group:         32768
> Fragments per group:      32768
> Inodes per group:         7824
> Inode blocks per group:   489
> Flex block group size:    16
> Filesystem created:       Sun Sep  7 15:13:09 2008
> Last mount time:          Tue Sep  8 15:19:44 2009
> Last write time:          Tue Sep  8 15:19:44 2009
> Mount count:              13
> Maximum mount count:      36
> Last checked:             Fri Sep  4 20:56:50 2009
> Check interval:           15552000 (6 months)
> Next check after:         Wed Mar  3 20:56:50 2010
> Lifetime writes:          1128 MB
> Reserved blocks uid:      0 (user root)
> Reserved blocks gid:      0 (group root)
> First inode:              11
> Inode size:	          256
> Required extra isize:     28
> Desired extra isize:      28
> Journal inode:            8
> Default directory hash:   tea
> Directory Hash Seed:      3c5f2a77-c446-4124-94f7-958ba6155f37
> Journal backup:           inode blocks
>> 4. Are image files  (first.img, middle.img and last.img)
>>    same as your previous mail?
>>    http://marc.info/?l=linux-ext4&m=124992522305319&w=2
> Yes.
>> 5. What arguments are set to EXT4_IOC_MOVE_EXT in your test case?
>         move_data.donor_fd = donor_fd;
>         move_data.orig_start = 0;
>         move_data.donor_start = 0;
>         move_data.len = SECTOR_TO_BLOCK(statbuf.st_blocks, fs.f_bsize); 
> 
>         err = ioctl(orig_fd, EXT4_IOC_MOVE_EXT, &move_data);

I tried to reproduce your problem with the following steps,
but I couldn't. Please check my procedure.

1. Test environment
linux2.6.31-rc2 + two patches as follows:
http://marc.info/?l=linux-ext4&m=125186152727422&w=3
http://marc.info/?l=linux-ext4&m=125205817410548&w=3

2. Create ext4 filesystem and mount it
mke2fs -t ext4 -b 4096 /dev/XXX
mount -t ext4 -O rw,noatime,relatime,commit=360 /dev/XXX /mnt/XXX

3. Create orig and donor files
dd if=/dev/urandom of=/mnt/XXX/first.img bs=10M count=1
dd if=/dev/zero of=/mnt/XXX/first.img bs=10M count=0 seek=50
dd if=/dev/urandom of=/mnt/XXX/last.img bs=10M count=1 seek=49

4. Call EXT4_MOVE_MOVE_EXT ioctl to files with the following arguments
(orig_file = /mnt/XXX/first.img, donor_file = /mnt/XXX/last.img)
move_data.orig_start = 0;
move_data.donor_start = 0;
move_data.len = 12152;
ioctl(orig_fd, EXT4_IOC_MOVE_EXT, &move_data)

However, EXT4_IOC_MOVE_EXT returned ENODATA (this is a fine result by my patch)
and it didn't occur the kernel panic which you got.
If I chose a wrong step, please correct me.

I appreciate if you could test following environment.
- 2.6.31-rc8 + ext4 patch queue
 (commit:bdacccd94d08a3f89e7fca676b28aa262c6d75fa) + attached patch

Regards,
Akira Fujita

---
 fs/ext4/move_extent.c |   72 +++++++++++++++++++++++++++++++++---------------
 1 files changed, 49 insertions(+), 23 deletions(-)

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 7bfbd58..7266247 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -25,6 +25,8 @@
 		if (IS_ERR(path)) {					\
 			ret = PTR_ERR(path);				\
 			path = NULL;					\
+		} else if (path[ext_depth(inode)].p_ext == NULL) {	\
+			ret = -ENODATA;					\
 		}							\
 	} while (0)

@@ -284,7 +286,7 @@ mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,

 	if (new_flag) {
 		get_ext_path(orig_path, orig_inode, eblock, err);
-		if (orig_path == NULL)
+		if (err)
 			goto out;

 		if (ext4_ext_insert_extent(handle, orig_inode,
@@ -295,7 +297,7 @@ mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,
 	if (end_flag) {
 		get_ext_path(orig_path, orig_inode,
 				      le32_to_cpu(end_ext->ee_block) - 1, err);
-		if (orig_path == NULL)
+		if (err)
 			goto out;

 		if (ext4_ext_insert_extent(handle, orig_inode,
@@ -554,8 +556,10 @@ mext_leaf_block(handle_t *handle, struct inode *orig_inode,
  * @orig_off:		block offset of original inode
  * @donor_off:		block offset of donor inode
  * @max_count:		the maximun length of extents
+ *
+ * Return 0 on success, or a negative error value on failure.
  */
-static void
+static int
 mext_calc_swap_extents(struct ext4_extent *tmp_dext,
 			      struct ext4_extent *tmp_oext,
 			      ext4_lblk_t orig_off, ext4_lblk_t donor_off,
@@ -564,6 +568,19 @@ mext_calc_swap_extents(struct ext4_extent *tmp_dext,
 	ext4_lblk_t diff, orig_diff;
 	struct ext4_extent dext_old, oext_old;

+	BUG_ON(orig_off != donor_off);
+
+	/* original and donor extents have to cover the same block offset */
+	if (orig_off < le32_to_cpu(tmp_oext->ee_block) ||
+	    le32_to_cpu(tmp_oext->ee_block) +
+			ext4_ext_get_actual_len(tmp_oext) - 1 < orig_off)
+		return -ENODATA;
+
+	if (orig_off < le32_to_cpu(tmp_dext->ee_block) ||
+	    le32_to_cpu(tmp_dext->ee_block) +
+			ext4_ext_get_actual_len(tmp_dext) - 1 < orig_off)
+		return -ENODATA;
+
 	dext_old = *tmp_dext;
 	oext_old = *tmp_oext;

@@ -591,6 +608,8 @@ mext_calc_swap_extents(struct ext4_extent *tmp_dext,

 	copy_extent_status(&oext_old, tmp_dext);
 	copy_extent_status(&dext_old, tmp_oext);
+
+	return 0;
 }

 /**
@@ -632,12 +651,12 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,

 	/* Get the original extent for the block "orig_off" */
 	get_ext_path(orig_path, orig_inode, orig_off, err);
-	if (orig_path == NULL)
+	if (err)
 		goto out;

 	/* Get the donor extent for the head */
 	get_ext_path(donor_path, donor_inode, donor_off, err);
-	if (donor_path == NULL)
+	if (err)
 		goto out;
 	depth = ext_depth(orig_inode);
 	oext = orig_path[depth].p_ext;
@@ -647,8 +666,10 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
 	dext = donor_path[depth].p_ext;
 	tmp_dext = *dext;

-	mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
+	err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
 				      donor_off, count);
+	if (err)
+		goto out;

 	/* Loop for the donor extents */
 	while (1) {
@@ -679,7 +700,7 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
 		if (orig_path)
 			ext4_ext_drop_refs(orig_path);
 		get_ext_path(orig_path, orig_inode, orig_off, err);
-		if (orig_path == NULL)
+		if (err)
 			goto out;
 		depth = ext_depth(orig_inode);
 		oext = orig_path[depth].p_ext;
@@ -694,7 +715,7 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
 			ext4_ext_drop_refs(donor_path);
 		get_ext_path(donor_path, donor_inode,
 				      donor_off, err);
-		if (donor_path == NULL)
+		if (err)
 			goto out;
 		depth = ext_depth(donor_inode);
 		dext = donor_path[depth].p_ext;
@@ -705,9 +726,10 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
 		}
 		tmp_dext = *dext;

-		mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
-					      donor_off,
-					      count - replaced_count);
+		err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
+					   donor_off, count - replaced_count);
+		if (err)
+			goto out;
 	}

 out:
@@ -1156,27 +1178,27 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
 		len -= block_end - file_end;

 	get_ext_path(orig_path, orig_inode, block_start, ret);
-	if (orig_path == NULL)
+	if (ret)
 		goto out2;

 	/* Get path structure to check the hole */
 	get_ext_path(holecheck_path, orig_inode, block_start, ret);
-	if (holecheck_path == NULL)
+	if (ret)
 		goto out;

 	depth = ext_depth(orig_inode);
 	ext_cur = holecheck_path[depth].p_ext;
-	if (ext_cur == NULL) {
-		ret = -EINVAL;
-		goto out;
-	}

 	/*
-	 * Get proper extent whose ee_block is beyond block_start
-	 * if block_start was within the hole.
+	 * Get proper starting location of block replacement if block_start was
+	 * within the hole.
 	 */
 	if (le32_to_cpu(ext_cur->ee_block) +
 		ext4_ext_get_actual_len(ext_cur) - 1 < block_start) {
+		/*
+		 * The hole exists between extents or the tail of
+		 * original file.
+		 */
 		last_extent = mext_next_extent(orig_inode,
 					holecheck_path, &ext_cur);
 		if (last_extent < 0) {
@@ -1189,8 +1211,12 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
 			ret = last_extent;
 			goto out;
 		}
-	}
-	seq_start = block_start;
+		seq_start = le32_to_cpu(ext_cur->ee_block);
+	} else if (le32_to_cpu(ext_cur->ee_block) > block_start)
+		/* The hole exists at the beginning of original file. */
+		seq_start = le32_to_cpu(ext_cur->ee_block);
+	else
+		seq_start = block_start;

 	/* No blocks within the specified range. */
 	if (le32_to_cpu(ext_cur->ee_block) > block_end) {
@@ -1292,7 +1318,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
 			ext4_ext_drop_refs(holecheck_path);
 		get_ext_path(holecheck_path, orig_inode,
 				      seq_start, ret);
-		if (holecheck_path == NULL)
+		if (ret)
 			break;
 		depth = holecheck_path->p_depth;

@@ -1300,7 +1326,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
 		if (orig_path)
 			ext4_ext_drop_refs(orig_path);
 		get_ext_path(orig_path, orig_inode, seq_start, ret);
-		if (orig_path == NULL)
+		if (ret)
 			break;

 		ext_cur = holecheck_path[depth].p_ext;