When dealing with catastrophic filesystem corruption on LUKS-encrypted ext4 partitions, the symptoms often appear suddenly with no obvious trigger. The case described shows multiple red flags:

# Typical error cascade seen in fsck output
Root inode is not a directory
Inode 2 has invalid size/block values
Multiple inodes show compression flags without support
HTree index corruption in directory inodes

Based on similar incidents reported in Linux kernel mailing lists and SSD failure studies, several possibilities emerge:

• SSD Controller Failure: Some Torx SSDs have shown firmware bugs causing silent corruption
• LUKS Layer Issues: dm-crypt errors during suspend/resume cycles
• Memory Corruption: Bad RAM causing corrupted writes to disk
• Journaling Failure: Ext4 journal not being properly replayed

Before attempting recovery, gather forensic data:

# Check for underlying device errors
sudo smartctl -a /dev/sdX | grep -E "Media_Wearout_Indicator|Reallocated_Sector|CRC_Error"

# Examine LUKS header integrity
sudo cryptsetup luksDump /dev/sdX

# Check memory for errors
sudo memtester 4G 1

When standard fsck fails, consider low-level approaches:

# Attempt to rebuild superblock from backup
sudo mke2fs -n /dev/mapper/vg-root
sudo fsck -b 32768 /dev/mapper/vg-root

# For LUKS-specific recovery:
sudo cryptsetup --debug open --type luks /dev/sdX temp_mapping
sudo dd if=/dev/mapper/temp_mapping bs=1M | strings | less

For future setups, consider these hardening steps:

# /etc/fstab options for SSD reliability
UUID=xxx / ext4 defaults,discard,noatime,nodiratime,data=journal,commit=60 0 1

# LUKS performance tuning
cryptsetup --pbkdf pbkdf2 --pbkdf-force-iterations 500000 luksFormat /dev/sdX

If the filesystem metadata is unrecoverable, proceed with:

1. Full disk image capture: sudo ddrescue /dev/sdX backup.img logfile
2. Secure erase SSD: sudo blkdiscard /dev/sdX
3. Fresh LUKS setup with improved parameters

Documenting the failure details (exact SSD model, kernel version, dm-crypt parameters) helps identify potential patterns with specific hardware/software combinations.

Seeing "Root inode is not a directory" during boot is every sysadmin's nightmare. This typically indicates catastrophic metadata corruption in ext4 filesystems - especially concerning when it affects both root and home partitions simultaneously. Let's examine the technical context of this failure:

# Typical failure pattern observed:
e2fsck -n /dev/mapper/vg-root
lithe_root was not cleanly unmounted
Root inode has dtime set
Inode 2 i_size shows impossible value (9581392125871137995)
HTree index corruption
Compression flags set on non-compressed FS

Before considering data recovery, we should rule out hardware issues:

# Check SSD health (even if SMART shows clean)
smartctl -a /dev/sda
# Test block layer integrity
badblocks -wsv /dev/mapper/vg-swap
# Verify LUKS header integrity
cryptsetup luksDump /dev/sda2

The simultaneous corruption across multiple LVs suggests either:

• Block layer corruption below LVM (SSD controller failure)
• Kernel memory corruption during writeback
• Encryption layer issues (though LUKS would typically fail more visibly)

When inodes show impossible values like i_size=9581392125871137995, we're typically seeing:

// Hypothetical inode structure corruption
struct ext4_inode {
  __le16 i_mode;    // Became 0xFFFF
  __le16 i_uid;     // Overwritten
  __le32 i_size_lo; // Random bits
  __le32 i_size_hi; // More random bits
  // ... other fields corrupted
};

Particularly suspicious findings in this case:

• Compression flags set without compression support
• HTree indexes (optimization for large directories) corrupted
• Reserved inodes (2-11) showing invalid modes

When facing this level of corruption, consider this sequence:

# 1. Attempt journal replay
e2fsck -E journal_only /dev/mapper/vg-root

# 2. Try alternate superblocks (if primary superblock is corrupt)
mkfs.ext4 -n /dev/mapper/vg-root  # Show superblock locations
e2fsck -b 32768 /dev/mapper/vg-root  # Use backup superblock

# 3. As last resort, metadata-based recovery
debugfs -R "ls -l" /dev/mapper/vg-root  # See if any files are accessible
photorec /dev/mapper/vg-root  # Raw file carving

For SSD-based LUKS/LVM systems:

• Enable metadata checksums (mkfs.ext4 -O metadata_csum)
• Consider ZFS for better corruption detection
• Monitor SSD wear metrics proactively
• Use dm-integrity beneath LUKS for additional protection

# Example dm-integrity setup:
cryptsetup luksFormat --integrity hmac-sha256 /dev/sda2
cryptsetup open --integrity hmac-sha256 /dev/sda2 ssd_crypt

The silent corruption pattern suggests either SSD firmware issues or rare kernel bugs. Consider testing with newer kernel versions and monitoring kernel.org for similar reports.