[BUG] NTFS rename fails with "Failed to add AT_INDEX_ALLOCATION" on Linux 7.1 new ntfs driver

Subject: [BUG] NTFS rename fails with "Failed to add AT_INDEX_ALLOCATION" on Linux 7.1 new ntfs driver

Summary:
========
On Linux 7.1 with the new in-kernel NTFS driver (NTFSPlus/NTFS_FS), 
rename() operations fail when the target directory's index inode MFT record 
is full. This manifests as "Disk write failure" in applications like Steam.

Reproduction:
=============
1. Mount an NTFS volume using the new "ntfs" driver (not ntfs3)
2. Create a directory with many files (or use a pre-existing Steam library)
3. Attempt to rename or create a new file in that directory
4. The operation fails with EIO, dmesg shows attribute add failures

Expected behavior:
==================
Rename succeeds, or at minimum returns a clear ENOSPC error if the filesystem 
is actually full.

Actual behavior:
================
dmesg shows cascading failures:
  ntfs: (device sdc1): ntfs_attr_add(): Failed to add resident attribute
  ntfs: (device sdc1): ntfs_ia_add(): Failed to add AT_INDEX_ALLOCATION
  ntfs: (device sdc1): ntfs_ir_make_space(): Failed to modify INDEX_ROOT

The application receives "Disk write failure" (EIO).

Root Cause Analysis:
====================
From code review of v7.1 fs/ntfs/index.c and fs/ntfs/attrib.c:

1. When a directory's INDEX_ROOT needs to grow beyond its current MFT record 
   space, ntfs_ir_make_space() (index.c:1309) is called.

2. If ntfs_ir_truncate() returns -ENOSPC, it calls ntfs_ir_reparent() 
   (index.c:1169) to move the index root into an index block.

3. ntfs_ir_reparent() calls ntfs_ia_add() (index.c:1143) to create the 
   AT_INDEX_ALLOCATION attribute.

4. ntfs_ia_add() calls ntfs_ibm_add() (index.c:919) to create the AT_BITMAP 
   attribute first.

5. ntfs_ibm_add() calls ntfs_attr_add() (attrib.c:2614) which tries to add 
   the AT_BITMAP as a resident attribute in the index inode's MFT record.

6. If the MFT record doesn't have enough free space 
   (bytes_allocated - bytes_in_use < attr_rec_size), ntfs_attr_add() fails 
   with ENOSPC.

7. Unlike ntfs3, the new driver doesn't attempt to allocate an extent MFT 
   record for the index inode before adding these attributes. It only tries 
   extent allocation for the base data inode, not for index inodes.

System Information:
===================
- Kernel: Linux 7.1.0-070100-generic
- Driver: ntfs (new NTFSPlus driver, CONFIG_NTFS_FS)
- Application: Steam (Left 4 Dead 2 update)
- Filesystem: NTFS 3.1, 4KB cluster size
- The same volume works correctly with ntfs3 driver

Workaround:
===========
Using "ntfs3" (CONFIG_NTFS3_FS) instead of "ntfs" works correctly.

Relevant dmesg output:
=====================
[1061.290832] ntfs: (device sdc1): ntfs_attr_add(): Failed to add non resident attribute
[1061.290837] ntfs: (device sdc1): ntfs_ia_add(): Failed to add AT_INDEX_ALLOCATION
[1061.290841] ntfs: (device sdc1): ntfs_ir_make_space(): Failed to modify INDEX_ROOT

Suggested Fix:
==============
In ntfs_ibm_add() or ntfs_ia_add(), if ntfs_attr_add() returns -ENOSPC,
the driver should attempt to allocate an extent MFT record for the index 
inode (icx->idx_ni) and add an attribute list before retrying the attribute 
addition. This is similar to how ntfs_attr_add() handles -ENOSPC for regular 
inodes via ntfs_inode_add_attrlist() + ntfs_mft_record_alloc().

Reporter: yi
Email: [email protected]

	
亓梦舰
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