btrfs-progs: add support ext4 unwritten file extent

This patch, along with the dependent patches below, adds support for ext4 unmerged unwritten file extents as preallocated file extent in btrfs.

btrfs-progs: convert: refactor ext2_create_file_extents add argument ext2_inode
btrfs-progs: convert: struct blk_iterate_data, add ext2-specific file inode pointers
btrfs-progs: convert: refactor __btrfs_record_file_extent to add a prealloc flag

The patch is developed with POV of portability with the current e2fsprogs library.

This patch will handle independent unwritten extents by marking them with prealloc flag and will identify merged unwritten extents, triggering a fail.

Testcase:

      $ dd if=/dev/urandom of=/mnt/test/foo bs=4K count=1 conv=fsync status=none
      $ dd if=/dev/urandom of=/mnt/test/foo bs=4K count=2 conv=fsync seek=1 status=none
      $ xfs_io -f -c 'falloc -k 12K 12K' /mnt/test/foo
      $ dd if=/dev/zero of=/mnt/test/foo bs=4K count=1 conv=fsync seek=6 status=none

      $ filefrag -v /mnt/test/foo
      Filesystem type is: ef53
      File size of /mnt/test/foo is 28672 (7 blocks of 4096 bytes)
	 ext:     logical_offset:        physical_offset: length:   expected: flags:
	   0:        0..       0:      33280..     33280:      1:
	   1:        1..       2:      33792..     33793:      2:      33281:
	   2:        3..       5:      33281..     33283:      3:      33794: unwritten
	   3:        6..       6:      33794..     33794:      1:      33284: last,eof

      $ sha256sum /mnt/test/foo
      18619b678a5c207a971a0aa931604f48162e307c57ecdec450d5f095fe9f32c7  /mnt/test/foo

    Convert and compare the checksum

    Before:

      $ filefrag -v /mnt/test/foo
      Filesystem type is: 9123683e
      File size of /mnt/test/foo is 28672 (7 blocks of 4096 bytes)
       ext:     logical_offset:        physical_offset: length:   expected: flags:
       0:        0..       0:      33280..     33280:      1:             shared
       1:        1..       2:      33792..     33793:      2:      33281: shared
       2:        3..       6:      33281..     33284:      4:      33794: last,shared,eof
      /mnt/test/foo: 3 extents found

      $ sha256sum /mnt/test/foo
      6874a1733e5785682210d69c07f256f684cf5433c7235ed29848b4a4d52030e0  /mnt/test/foo

    After:

      $ filefrag -v /mnt/test/foo
      Filesystem type is: 9123683e
      File size of /mnt/test/foo is 28672 (7 blocks of 4096 bytes)
	 ext:     logical_offset:        physical_offset: length:   expected: flags:
	   0:        0..       0:      33280..     33280:      1:             shared
	   1:        1..       2:      33792..     33793:      2:      33281: shared
	   2:        3..       5:      33281..     33283:      3:      33794: unwritten,shared
	   3:        6..       6:      33794..     33794:      1:      33284: last,shared,eof
      /mnt/test/foo: 4 extents found

      $ sha256sum /mnt/test/foo
      18619b678a5c207a971a0aa931604f48162e307c57ecdec450d5f095fe9f32c7  /mnt/test/foo

Signed-off-by Anand Jain <[email protected]>

---
v2:

. Remove RFC
. Identify the block with a merged preallocated extent and call fail-safe . Qu has an idea that it could be marked as a hole, which may be based on
top of this patch.

convert/source-ext2.c +12 -0

+
+	memset(&extent, 0, sizeof(struct ext2fs_extent));
+	if (ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent)) {
+		error("ext2fs_extent_get EXT2_EXTENT_CURRENT failed inode %d",
+		       src->ext2_ino);
+		ext2fs_extent_free(handle);
+		return -EINVAL;
+	}
+
+	if (extent.e_pblk != data->disk_block) {
+	error("inode %d index %d found wrong extent e_pblk %llu wanted disk_block %llu",
+		       src->ext2_ino, index, extent.e_pblk, data->disk_block);

convert/source-ext2.c +7 -0

+
+	if (extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT)
+		*has_unwritten = true;
+
+	return 0;
+}
+
  static int ext2_dir_iterate_proc(ext2_ino_t dir, int entry,
  			    struct ext2_dir_entry *dirent,
  			    int offset, int blocksize,

convert/source-ext2.h +3 -0

index 026a7cad8ac8..19014d3c25e6 100644
@@ -82,6 +82,9 @@ struct ext2_source_fs {
  	ext2_ino_t ext2_ino;
  };
 
+int ext2_find_unwritten(struct blk_iterate_data *data, int index,
+			bool *has_unwritten);
+
  #define EXT2_ACL_VERSION	0x0001
 
  #endif	/* BTRFSCONVERT_EXT2 */

convert/source-fs.c +23 -2

index df5ce66caf7f..88a6ceaf41f6 100644
@@ -31,6 +31,7 @@
  #include "common/extent-tree-utils.h"
  #include "convert/common.h"
  #include "convert/source-fs.h"
+#include "convert/source-ext2.h"
 
  const struct simple_range btrfs_reserved_ranges[3] = {
  	{ 0,			     SZ_1M },

@@ -239,6 +240,15 @@ fail:
  	return ret;
  }
 
+int find_prealloc(struct blk_iterate_data *data, int index,
+		  bool *has_prealloc)
+{
+	if (data->source_fs)
+		return ext2_find_unwritten(data, index, has_prealloc);
+
+	return -EINVAL;
+}
+
  /*
   * Record a file extent in original filesystem into btrfs one.
   * The special point is, old disk_block can point to a reserved range.

@@ -257,6 +267,7 @@ int record_file_blocks(struct blk_iterate_data *data,
  	u64 old_disk_bytenr = disk_block * sectorsize;
  	u64 num_bytes = num_blocks * sectorsize;
  	u64 cur_off = old_disk_bytenr;
+	int index = data->first_block;
 
  	/* Hole, pass it to record_file_extent directly */
  	if (old_disk_bytenr == 0)

@@ -276,6 +287,16 @@ int record_file_blocks(struct blk_iterate_data *data,
  		u64 extent_num_bytes;
  		u64 real_disk_bytenr;
  		u64 cur_len;
+		u64 flags = BTRFS_FILE_EXTENT_REG;
+		bool has_prealloc = false;
+
+		if (find_prealloc(data, index, &has_prealloc)) {
+			data->errcode = -1;
+			return -EINVAL;
+		}
+
+		if (has_prealloc)
+			flags = BTRFS_FILE_EXTENT_PREALLOC;
 
  		key.objectid = data->convert_ino;
  		key.type = BTRFS_EXTENT_DATA_KEY;

@@ -316,12 +337,12 @@ int record_file_blocks(struct blk_iterate_data *data,
  			      old_disk_bytenr + num_bytes) - cur_off;
  		ret = btrfs_record_file_extent(data->trans, data->root,
  					data->objectid, data->inode, file_pos,
-					real_disk_bytenr, cur_len,
-					BTRFS_FILE_EXTENT_REG);
+					real_disk_bytenr, cur_len, flags);
  		if (ret < 0)
  			break;
  		cur_off += cur_len;
  		file_pos += cur_len;
+		index++;
 
  		/*
  		 * No need to care about csum

convert/source-fs.h +1 -0

index 25916c65681b..db7ead422585 100644
@@ -153,5 +153,6 @@ int read_disk_extent(struct btrfs_root *root, u64 bytenr,
  		            u32 num_bytes, char *buffer);
  int record_file_blocks(struct blk_iterate_data *data,
  			      u64 file_block, u64 disk_block, u64 num_blocks);
+int find_prealloc(struct blk_iterate_data *data, int index, bool *has_prealloc);
 
  #endif

Quoted 66 lines · Anand Jain

This patch, along with the dependent patches below, adds support for ext4 unmerged  unwritten file extents as preallocated file extent in btrfs.

  btrfs-progs: convert: refactor ext2_create_file_extents add argument ext2_inode
  btrfs-progs: convert: struct blk_iterate_data, add ext2-specific file inode pointers
  btrfs-progs: convert: refactor __btrfs_record_file_extent to add a prealloc flag

The patch is developed with POV of portability with the current e2fsprogs library.

This patch will handle independent unwritten extents by marking them with prealloc flag and will identify merged unwritten extents, triggering a fail.

Testcase:

      $ dd if=/dev/urandom of=/mnt/test/foo bs=4K count=1 conv=fsync status=none
      $ dd if=/dev/urandom of=/mnt/test/foo bs=4K count=2 conv=fsync seek=1 status=none
      $ xfs_io -f -c 'falloc -k 12K 12K' /mnt/test/foo
      $ dd if=/dev/zero of=/mnt/test/foo bs=4K count=1 conv=fsync seek=6 status=none

      $ filefrag -v /mnt/test/foo
      Filesystem type is: ef53
      File size of /mnt/test/foo is 28672 (7 blocks of 4096 bytes)
     ext:     logical_offset:        physical_offset: length:   expected: flags:
       0:        0..       0:      33280..     33280:      1:
       1:        1..       2:      33792..     33793:      2:      33281:
       2:        3..       5:      33281..     33283:      3:      33794: unwritten
       3:        6..       6:      33794..     33794:      1:      33284: last,eof

      $ sha256sum /mnt/test/foo

18619b678a5c207a971a0aa931604f48162e307c57ecdec450d5f095fe9f32c7 /mnt/test/foo

    Convert and compare the checksum

    Before:

      $ filefrag -v /mnt/test/foo
      Filesystem type is: 9123683e
      File size of /mnt/test/foo is 28672 (7 blocks of 4096 bytes)
       ext:     logical_offset:        physical_offset: length:   expected: flags:
       0:        0..       0:      33280..     33280:      1:             shared
       1:        1..       2:      33792..     33793:      2:      33281: shared
       2:        3..       6:      33281..     33284:      4:      33794: last,shared,eof
      /mnt/test/foo: 3 extents found

      $ sha256sum /mnt/test/foo

6874a1733e5785682210d69c07f256f684cf5433c7235ed29848b4a4d52030e0 /mnt/test/foo

    After:

      $ filefrag -v /mnt/test/foo
      Filesystem type is: 9123683e
      File size of /mnt/test/foo is 28672 (7 blocks of 4096 bytes)
     ext:     logical_offset:        physical_offset: length:   expected: flags:
       0:        0..       0:      33280..     33280:      1:             shared
       1:        1..       2:      33792..     33793:      2:      33281: shared
       2:        3..       5:      33281..     33283:      3:      33794: unwritten,shared
       3:        6..       6:      33794..     33794:      1:      33284: last,shared,eof
      /mnt/test/foo: 4 extents found

      $ sha256sum /mnt/test/foo

18619b678a5c207a971a0aa931604f48162e307c57ecdec450d5f095fe9f32c7 /mnt/test/foo

Quoted 8 lines

Signed-off-by Anand Jain <[email protected]>

---
v2:

. Remove RFC
. Identify the block with a merged preallocated extent and call fail-safe . Qu has an idea that it could be marked as a hole, which may be based on top of this patch.

Well, my idea of going holes other than preallocated extents is mostly to avoid the extra @prealloc flag parameter.

But that's not a big deal for now, as I found the following way to easily crack your v2 patchset:

  # fallocate -l 1G test.img
  # mkfs.ext4 -F test.img
  # mount test.img $mnt
  # xfs_io -f -c "falloc 0 16K" $mnt/file
  # sync
  # xfs_io -f -c "pwrite 0 4k" -c "pwrite 12k 4k" $mnt/file
  # umount $mnt
  # ./btrfs-convert test.img
btrfs-convert from btrfs-progs v6.8

Source filesystem:
  Type:           ext2
  Label:
  Blocksize:      4096
  UUID:           0f98aa2a-b1ee-4e91-8815-9b9a7b4af00a
Target filesystem:
  Label:
  Blocksize:      4096
  Nodesize:       16384
  UUID:           3b8db399-8e25-495b-a41c-47afcb672020 Checksum:       crc32c
  Features:       extref, skinny-metadata, no-holes, free-space-tree
(default)
    Data csum:    yes
    Inline data:  yes
    Copy xattr:   yes
Reported stats:
  Total space:      1073741824
  Free space:        872349696 (81.24%)
  Inode count:           65536
  Free inodes:           65523
  Block count:          262144
Create initial btrfs filesystem
Create ext2 image file
Create btrfs metadata
ERROR: inode 13 index 0: identified unsupported merged block length 1 wanted 4
ERROR: failed to copy ext2 inode 13: -22
ERROR: error during copy_inodes -22
WARNING: error during conversion, the original filesystem is not modified

[...]

Quoted 16 lines

convert/source-ext2.c +11 -0

+
+    memset(&extent, 0, sizeof(struct ext2fs_extent));
+    if (ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent)) {
+        error("ext2fs_extent_get EXT2_EXTENT_CURRENT failed inode %d",
+               src->ext2_ino);
+        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }
+
+    if (extent.e_pblk != data->disk_block) {
+    error("inode %d index %d found wrong extent e_pblk %llu wanted 

disk_block %llu",
+               src->ext2_ino, index, extent.e_pblk, data->disk_block); +        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }

Quoted 8 lines

+
+    if (extent.e_len != data->num_blocks) {
+    error("inode %d index %d: identified unsupported merged block length %u wanted %llu",
+            src->ext2_ino, index, extent.e_len, data->num_blocks); +        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }

You have to split the extent in this case. As the example I gave, part of the extent can have been written.
(And I'm not sure if the e_pblk check is also correct)

I believe the example I gave could be a pretty good test case. (Or you can go one step further to interleave every 4K)

Thanks,
Qu

Quoted 107 lines

convert/source-ext2.c +7 -0

+
+    if (extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT)
+        *has_unwritten = true;
+
+    return 0;
+}
+

  static int ext2_dir_iterate_proc(ext2_ino_t dir, int entry, struct ext2_dir_entry *dirent, int offset, int blocksize,

convert/source-ext2.h +3 -0

index 026a7cad8ac8..19014d3c25e6 100644
@@ -82,6 +82,9 @@ struct ext2_source_fs {
       ext2_ino_t ext2_ino;
   };
 
+int ext2_find_unwritten(struct blk_iterate_data *data, int index,
+            bool *has_unwritten);
+
   #define EXT2_ACL_VERSION    0x0001
 
   #endif    /* BTRFSCONVERT_EXT2 */

convert/source-fs.c +21 -0

index df5ce66caf7f..88a6ceaf41f6 100644
@@ -31,6 +31,7 @@
   #include "common/extent-tree-utils.h"
   #include "convert/common.h"
   #include "convert/source-fs.h"
+#include "convert/source-ext2.h"
 
   const struct simple_range btrfs_reserved_ranges[3] = {
       { 0,                 SZ_1M },

@@ -239,6 +240,15 @@ fail:
       return ret;
   }
 
+int find_prealloc(struct blk_iterate_data *data, int index,
+          bool *has_prealloc)
+{
+    if (data->source_fs)
+        return ext2_find_unwritten(data, index, has_prealloc);
+
+    return -EINVAL;
+}
+
   /*
    * Record a file extent in original filesystem into btrfs one.
    * The special point is, old disk_block can point to a reserved range.

@@ -257,6 +267,7 @@ int record_file_blocks(struct blk_iterate_data *data,
       u64 old_disk_bytenr = disk_block * sectorsize;
       u64 num_bytes = num_blocks * sectorsize;
       u64 cur_off = old_disk_bytenr;
+    int index = data->first_block;
 
       /* Hole, pass it to record_file_extent directly */
       if (old_disk_bytenr == 0)

@@ -276,6 +287,16 @@ int record_file_blocks(struct blk_iterate_data 
 *data,
           u64 extent_num_bytes;
           u64 real_disk_bytenr;
           u64 cur_len;
+        u64 flags = BTRFS_FILE_EXTENT_REG;
+        bool has_prealloc = false;
+
+        if (find_prealloc(data, index, &has_prealloc)) {
+            data->errcode = -1;
+            return -EINVAL;
+        }
+
+        if (has_prealloc)
+            flags = BTRFS_FILE_EXTENT_PREALLOC;
 
           key.objectid = data->convert_ino;

          key.type = BTRFS_EXTENT_DATA_KEY;

convert/source-fs.c +2 -2

@@ -316,12 +337,12 @@ int record_file_blocks(struct blk_iterate_data 
 *data,
                     old_disk_bytenr + num_bytes) - cur_off;
           ret = btrfs_record_file_extent(data->trans, data->root,
                       data->objectid, data->inode, file_pos,
-                    real_disk_bytenr, cur_len,
-                    BTRFS_FILE_EXTENT_REG);
+                    real_disk_bytenr, cur_len, flags);
           if (ret < 0)
               break;
           cur_off += cur_len;
           file_pos += cur_len;
+        index++;
 
           /*

           * No need to care about csum

convert/source-fs.h +1 -0

index 25916c65681b..db7ead422585 100644
@@ -153,5 +153,6 @@ int read_disk_extent(struct btrfs_root *root, u64 
 bytenr,
                       u32 num_bytes, char *buffer);
   int record_file_blocks(struct blk_iterate_data *data,
                     u64 file_block, u64 disk_block, u64 num_blocks);
+int find_prealloc(struct blk_iterate_data *data, int index, bool 
 *has_prealloc);

  #endif

Quoted 11 lines

Quoted 5 lines

. Remove RFC
. Identify the block with a merged preallocated extent and call fail-safe . Qu has an idea that it could be marked as a hole, which may be based on top of this patch.

Well, my idea of going holes other than preallocated extents is mostly to avoid the extra @prealloc flag parameter.

But that's not a big deal for now, as I found the following way to easily crack your v2 patchset:

Quoted 75 lines

  # fallocate -l 1G test.img
  # mkfs.ext4 -F test.img
  # mount test.img $mnt
  # xfs_io -f -c "falloc 0 16K" $mnt/file
  # sync
  # xfs_io -f -c "pwrite 0 4k" -c "pwrite 12k 4k" $mnt/file
  # umount $mnt
  # ./btrfs-convert test.img
btrfs-convert from btrfs-progs v6.8

Source filesystem:
   Type:           ext2
   Label:
   Blocksize:      4096
   UUID:           0f98aa2a-b1ee-4e91-8815-9b9a7b4af00a Target filesystem:
   Label:
   Blocksize:      4096
   Nodesize:       16384
   UUID:           3b8db399-8e25-495b-a41c-47afcb672020 Checksum:       crc32c
   Features:       extref, skinny-metadata, no-holes, free-space-tree (default)
     Data csum:    yes
     Inline data:  yes
     Copy xattr:   yes
Reported stats:
   Total space:      1073741824
   Free space:        872349696 (81.24%)
   Inode count:           65536
   Free inodes:           65523
   Block count:          262144
Create initial btrfs filesystem
Create ext2 image file
Create btrfs metadata
ERROR: inode 13 index 0: identified unsupported merged block length 1 wanted 4
ERROR: failed to copy ext2 inode 13: -22
ERROR: error during copy_inodes -22
WARNING: error during conversion, the original filesystem is not modified

[...]

Quoted 16 lines

convert/source-ext2.c +11 -0

+
+    memset(&extent, 0, sizeof(struct ext2fs_extent));
+    if (ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent)) {
+        error("ext2fs_extent_get EXT2_EXTENT_CURRENT failed inode %d",
+               src->ext2_ino);
+        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }
+
+    if (extent.e_pblk != data->disk_block) {
+    error("inode %d index %d found wrong extent e_pblk %llu wanted 

disk_block %llu",
+               src->ext2_ino, index, extent.e_pblk, data->disk_block); +        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }

Quoted 8 lines

+
+    if (extent.e_len != data->num_blocks) {
+    error("inode %d index %d: identified unsupported merged block length %u wanted %llu",
+            src->ext2_ino, index, extent.e_len, data->num_blocks); +        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }

You have to split the extent in this case. As the example I gave, part of the extent can have been written.
(And I'm not sure if the e_pblk check is also correct)

Quoted 2 lines

I believe the example I gave could be a pretty good test case. (Or you can go one step further to interleave every 4K)

Furthermore, I have to consider what is the best way to iterate all data extents of an ext2 inode.

Instead of ext2fs_block_iterate2(), I'm wondering if ext2fs_extent_goto() would be a better solution. (As long as if it can handle holes).

Another thing is, please Cc this series to ext4 mailing list if possible.
I hope to get some feedback from the ext4 exports as they may have a much better idea than us.

Quoted 11 lines

Quoted 11 lines

Quoted 5 lines

. Remove RFC
. Identify the block with a merged preallocated extent and call fail-safe . Qu has an idea that it could be marked as a hole, which may be based on top of this patch.

Well, my idea of going holes other than preallocated extents is mostly to avoid the extra @prealloc flag parameter.

But that's not a big deal for now, as I found the following way to easily crack your v2 patchset:

This patch and the below test case are working as designed it is not
a bug/crack, with the current limitation that it should fail (safer
than silent corruption) (as shown below) when there is a merged unwritten data extent.

  ERROR: inode 13 index 0: identified unsupported merged block length 1
wanted 4

This is an intermediary stage while the full support is being added.

Given this option, the user will have a choice to work on the identified inode and make it a non-unwritten extent so that btrfs-convert shall be successful.

Quoted 80 lines

Quoted 77 lines

  # fallocate -l 1G test.img
  # mkfs.ext4 -F test.img
  # mount test.img $mnt
  # xfs_io -f -c "falloc 0 16K" $mnt/file
  # sync
  # xfs_io -f -c "pwrite 0 4k" -c "pwrite 12k 4k" $mnt/file
  # umount $mnt
  # ./btrfs-convert test.img
btrfs-convert from btrfs-progs v6.8

Source filesystem:
   Type:           ext2
   Label:
   Blocksize:      4096
   UUID:           0f98aa2a-b1ee-4e91-8815-9b9a7b4af00a Target filesystem:
   Label:
   Blocksize:      4096
   Nodesize:       16384
   UUID:           3b8db399-8e25-495b-a41c-47afcb672020 Checksum:       crc32c
   Features:       extref, skinny-metadata, no-holes, free-space-tree (default)
     Data csum:    yes
     Inline data:  yes
     Copy xattr:   yes
Reported stats:
   Total space:      1073741824
   Free space:        872349696 (81.24%)
   Inode count:           65536
   Free inodes:           65523
   Block count:          262144
Create initial btrfs filesystem
Create ext2 image file
Create btrfs metadata
ERROR: inode 13 index 0: identified unsupported merged block length 1 wanted 4
ERROR: failed to copy ext2 inode 13: -22
ERROR: error during copy_inodes -22
WARNING: error during conversion, the original filesystem is not modified

[...]

Quoted 16 lines

convert/source-ext2.c +11 -0

+
+    memset(&extent, 0, sizeof(struct ext2fs_extent));
+    if (ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent)) {
+        error("ext2fs_extent_get EXT2_EXTENT_CURRENT failed inode %d",
+               src->ext2_ino);
+        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }
+
+    if (extent.e_pblk != data->disk_block) {
+    error("inode %d index %d found wrong extent e_pblk %llu wanted 

disk_block %llu",
+               src->ext2_ino, index, extent.e_pblk, data->disk_block); +        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }

Quoted 8 lines

+
+    if (extent.e_len != data->num_blocks) {
+    error("inode %d index %d: identified unsupported merged block length %u wanted %llu",
+            src->ext2_ino, index, extent.e_len, data->num_blocks); +        ext2fs_extent_free(handle);
+        return -EINVAL;
+    }

You have to split the extent in this case. As the example I gave, part of the extent can have been written.
(And I'm not sure if the e_pblk check is also correct)

Quoted 2 lines

I believe the example I gave could be a pretty good test case. (Or you can go one step further to interleave every 4K)

Quoted 7 lines

Furthermore, I have to consider what is the best way to iterate all data extents of an ext2 inode.

Instead of ext2fs_block_iterate2(), I'm wondering if ext2fs_extent_goto() would be a better solution. (As long as if it can handle holes).

Another thing is, please Cc this series to ext4 mailing list if possible.
I hope to get some feedback from the ext4 exports as they may have a much better idea than us.

I've tried fixes without success. Empirically, I found that the main issue is extent optimization and merging, which ignores the unwritten flag, idk where is this happening. I think it is during writing the ext4 image at the inode BTRFS_FIRST_FREE_OBJECTID + 1.

If avoiding this optimization possible, the extent boundary will align with ext4 and thus its flags.

Thanks, Anand

      18619b678a5c207a971a0aa931604f48162e307c57ecdec450d5f095fe9f32c7  /mnt/test/foo

Signed-off-by Anand Jain <[email protected]>

---
v2:

. Remove RFC

convert/source-ext2.c +19 -0

+
+	if (ext2fs_extent_goto2(handle, 0, index)) {
+		error("ext2fs_extent_goto2 failed, inode %d num_blocks %llu",
+		       src->ext2_ino, data->num_blocks);
+		ext2fs_extent_free(handle);
+		return -EINVAL;
+	}
+
+	memset(&extent, 0, sizeof(struct ext2fs_extent));
+	if (ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent)) {
+		error("ext2fs_extent_get EXT2_EXTENT_CURRENT failed inode %d",
+		       src->ext2_ino);
+		ext2fs_extent_free(handle);
+		return -EINVAL;
+	}
+
+	if (extent.e_pblk != data->disk_block) {
+	error("inode %d index %d found wrong extent e_pblk %llu wanted disk_block %llu",
+		       src->ext2_ino, index, extent.e_pblk, data->disk_block);

在 2024/5/6 12:34, Anand Jain 写道:
[...]

Quoted 7 lines

18619b678a5c207a971a0aa931604f48162e307c57ecdec450d5f095fe9f32c7 /mnt/test/foo

Signed-off-by Anand Jain <[email protected]>

---
v2:

Quoted 1 line

. Remove RFC

Nope, you didn't even test the patch using the selftests. (Despite the RST introduced failure, the first ext2 is enough to expose your bug).