4K inode support on 4Kn device

4K inode support on 4Kn device

[Wang Yugui]

Hi,

I want to support 4K inode on 4Kn device.

1,  change the size of XFS_DINODE_MAX_SIZE/XFS_DINODE_MAX_LOG
     to 4096/12 from 2048/11.

2, do we need to keep the following restriction in man mkfs.xfs?
    the inode size cannot exceed one half of the filesystem block size.

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2026/04/21

Re: 4K inode support on 4Kn device

[Carlos Maiolino]

On Tue, Apr 21, 2026 at 09:42:05AM +0800, Wang Yugui wrote:
> Hi,
> 
> I want to support 4K inode on 4Kn device.
> 
> 1,  change the size of XFS_DINODE_MAX_SIZE/XFS_DINODE_MAX_LOG
>      to 4096/12 from 2048/11.
> 
> 2, do we need to keep the following restriction in man mkfs.xfs?
>     the inode size cannot exceed one half of the filesystem block size.

Can you please better detail what are you trying to achieve with 4KiB
inodes?


> 
> Best Regards
> Wang Yugui (wangyugui@e16-tech.com)
> 2026/04/21
> 
> 
> 

[PATCH] xfsprogs: 4K inode support

[Wang Yugui]

---
 include/xfs_multidisk.h | 2 +-
 libxfs/xfs_format.h     | 2 +-
 libxfs/xfs_sb.c         | 1 +
 man/man8/mkfs.xfs.8.in  | 3 +--
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/xfs_multidisk.h b/include/xfs_multidisk.h
index ef4443b0bb0e..b77a915811f9 100644
--- a/include/xfs_multidisk.h
+++ b/include/xfs_multidisk.h
@@ -14,7 +14,7 @@
 #define	XFS_DFL_BLOCKSIZE_LOG	12		/* 4096 byte blocks */
 #define	XFS_DINODE_DFL_LOG	8		/* 256 byte inodes */
 #define	XFS_DINODE_DFL_CRC_LOG	9		/* 512 byte inodes for CRCs */
-#define	XFS_MIN_INODE_PERBLOCK	2		/* min inodes per block */
+#define	XFS_MIN_INODE_PERBLOCK	1		/* min inodes per block */
 #define	XFS_DFL_IMAXIMUM_PCT	25		/* max % of space for inodes */
 #define	XFS_MIN_REC_DIRSIZE	12		/* 4096 byte dirblocks (V2) */
 #define XFS_MAX_INODE_SIG_BITS	32		/* most significant bits in an
diff --git a/libxfs/xfs_format.h b/libxfs/xfs_format.h
index 779dac59b1f3..84cce8d268e6 100644
--- a/libxfs/xfs_format.h
+++ b/libxfs/xfs_format.h
@@ -1079,7 +1079,7 @@ enum xfs_dinode_fmt {
  * Inode minimum and maximum sizes.
  */
 #define	XFS_DINODE_MIN_LOG	8
-#define	XFS_DINODE_MAX_LOG	11
+#define	XFS_DINODE_MAX_LOG	12
 #define	XFS_DINODE_MIN_SIZE	(1 << XFS_DINODE_MIN_LOG)
 #define	XFS_DINODE_MAX_SIZE	(1 << XFS_DINODE_MAX_LOG)
 
diff --git a/libxfs/xfs_sb.c b/libxfs/xfs_sb.c
index dd14c3ab3b59..9c57d13e50bc 100644
--- a/libxfs/xfs_sb.c
+++ b/libxfs/xfs_sb.c
@@ -717,6 +717,7 @@ xfs_validate_sb_common(
 	case 512:
 	case 1024:
 	case 2048:
+	case 4096:
 		break;
 	default:
 		xfs_warn(mp, "inode size of %d bytes not supported",
diff --git a/man/man8/mkfs.xfs.8.in b/man/man8/mkfs.xfs.8.in
index fbafc5c79e02..b0a2222d370d 100644
--- a/man/man8/mkfs.xfs.8.in
+++ b/man/man8/mkfs.xfs.8.in
@@ -638,8 +638,7 @@ The minimum (and default)
 is 256 bytes without crc, 512 bytes with crc enabled.
 The maximum
 .I value
-is 2048 (2 KiB) subject to the restriction that
-the inode size cannot exceed one half of the filesystem block size.
+is 4096 (4 KiB).
 .IP
 XFS uses 64-bit inode numbers internally; however, the number of
 significant bits in an inode number
-- 
2.36.2

[ RFC ] xfs: 4K inode support

[Wang Yugui]

use case for 4K inode
- simpler logic for 4Kn device, and less lock.
- better performance for directory with many files.
- maybe inline data support later.

TODO:
still crash in xfs_trans_read_buf_map() when mount a 4K inode xfs now.

---
 fs/xfs/libxfs/xfs_format.h   | 2 +-
 fs/xfs/libxfs/xfs_metafile.c | 2 +-
 fs/xfs/libxfs/xfs_sb.c       | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 779dac59b1f3..84cce8d268e6 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -1079,7 +1079,7 @@ enum xfs_dinode_fmt {
  * Inode minimum and maximum sizes.
  */
 #define	XFS_DINODE_MIN_LOG	8
-#define	XFS_DINODE_MAX_LOG	11
+#define	XFS_DINODE_MAX_LOG	12
 #define	XFS_DINODE_MIN_SIZE	(1 << XFS_DINODE_MIN_LOG)
 #define	XFS_DINODE_MAX_SIZE	(1 << XFS_DINODE_MAX_LOG)
 
diff --git a/fs/xfs/libxfs/xfs_metafile.c b/fs/xfs/libxfs/xfs_metafile.c
index cf239f862212..9db799576775 100644
--- a/fs/xfs/libxfs/xfs_metafile.c
+++ b/fs/xfs/libxfs/xfs_metafile.c
@@ -98,7 +98,7 @@ xfs_metafile_resv_can_cover(
 	 * isn't critical unless there also isn't enough free space.
 	 */
 	return xfs_compare_freecounter(mp, XC_FREE_BLOCKS,
-			rhs - mp->m_metafile_resv_avail, 2048) >= 0;
+			rhs - mp->m_metafile_resv_avail, 4096) >= 0;
 }
 
 /*
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 38d16fe1f6d8..39424a7c74df 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -734,6 +734,7 @@ xfs_validate_sb_common(
 	case 512:
 	case 1024:
 	case 2048:
+	case 4096:
 		break;
 	default:
 		xfs_warn(mp, "inode size of %d bytes not supported",
-- 
2.36.2