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-rw-r--r--fs/xfs/Kconfig24
-rw-r--r--fs/xfs/xfs_super.c13
2 files changed, 37 insertions, 0 deletions
diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig
index e685299eb3d2..5422227e9e93 100644
--- a/fs/xfs/Kconfig
+++ b/fs/xfs/Kconfig
@@ -22,6 +22,30 @@ config XFS_FS
system of your root partition is compiled as a module, you'll need
to use an initial ramdisk (initrd) to boot.
+config XFS_SUPPORT_V4
+ bool "Support deprecated V4 (crc=0) format"
+ default y
+ help
+ The V4 filesystem format lacks certain features that are supported
+ by the V5 format, such as metadata checksumming, strengthened
+ metadata verification, and the ability to store timestamps past the
+ year 2038. Because of this, the V4 format is deprecated. All users
+ should upgrade by backing up their files, reformatting, and restoring
+ from the backup.
+
+ Administrators and users can detect a V4 filesystem by running
+ xfs_info against a filesystem mountpoint and checking for a string
+ beginning with "crc=". If the string "crc=0" is found, the
+ filesystem is a V4 filesystem. If no such string is found, please
+ upgrade xfsprogs to the latest version and try again.
+
+ This option will become default N in September 2025. Support for the
+ V4 format will be removed entirely in September 2030. Distributors
+ can say N here to withdraw support earlier.
+
+ To continue supporting the old V4 format (crc=0), say Y.
+ To close off an attack surface, say N.
+
config XFS_QUOTA
bool "XFS Quota support"
depends on XFS_FS
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index baf5de30eebb..bb1d079b690d 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1450,6 +1450,19 @@ xfs_fc_fill_super(
if (error)
goto out_free_sb;
+ /* V4 support is undergoing deprecation. */
+ if (!xfs_sb_version_hascrc(&mp->m_sb)) {
+#ifdef CONFIG_XFS_SUPPORT_V4
+ xfs_warn_once(mp,
+ "Deprecated V4 format (crc=0) will not be supported after September 2030.");
+#else
+ xfs_warn(mp,
+ "Deprecated V4 format (crc=0) not supported by kernel.");
+ error = -EINVAL;
+ goto out_free_sb;
+#endif
+ }
+
/*
* XFS block mappings use 54 bits to store the logical block offset.
* This should suffice to handle the maximum file size that the VFS