From 319d2735f99e95955c2a75c8fc6282ddf7de232a Mon Sep 17 00:00:00 2001 From: "Yann E. MORIN" Date: Sun, 20 Nov 2022 21:42:26 +0100 Subject: [PATCH] fs/ext2: generate Y2K38-resilient filesystems When creating a filesystem, mkfs.ext will chose the inode size depending on the size of the filesystem. Small filesystem get 128-bytes inodes, while bigger filesystems use 256-byte inodes (inode must be a power of 2 larger or equal to 128, and smaller or equal to the blocksize). However, 128-byte inodes can't store timestamps past the dreaded 2038-01-19 03:14:07Z deadline, while inodes larger than or equal to 256 do not have the issue. It turns out that the tipping point to decide whether a filesystem is small or big, is about around the size of the filesystems we generate for our runtime tests. This causes the kernel to emit warning like: ext2 filesystem being remounted at / supports timestamps until 2038 (0x7fffffff) We add a new option to our ext2 filesystem, so that user can specify the size of the inode. That new option defaults to 256 to be resilient to the Y2K38 problem. Note: it was already possible for users to explicitly pass the -I option, through BR2_TARGET_ROOTFS_EXT2_MKFS_OPTIONS. We could have chosen to extend the existing value with a -I 256, but that is not satisfactory. Indeed, we do want to ensure that the default is now Y2K38-OK, even for existing configurations that did not have explicit setting. We also pass that new option before the user-specified arbitrary ones, so that BR2_TARGET_ROOTFS_EXT2_MKFS_OPTIONS still wins (in case -I was set there). Signed-off-by: Yann E. MORIN [Peter: tweak help text] Signed-off-by: Peter Korsgaard --- fs/ext2/Config.in | 13 +++++++++++++ fs/ext2/ext2.mk | 1 + 2 files changed, 14 insertions(+) diff --git a/fs/ext2/Config.in b/fs/ext2/Config.in index 705446df57..4451d0797f 100644 --- a/fs/ext2/Config.in +++ b/fs/ext2/Config.in @@ -60,6 +60,19 @@ config BR2_TARGET_ROOTFS_EXT2_INODES int "exact number of inodes (leave at 0 for auto calculation)" default 0 +config BR2_TARGET_ROOTFS_EXT2_INODE_SIZE + int "inode size" + default 256 + help + Set the size of inodes, in bytes, as a power of 2 larger or + equal to 128. + + Set to 0 to let the filesystem generator decide based on the + file system size. If unsure, keep the default, 256. + + Note: 128-byte inodes suffer of the Y2K38 problem, and can't + store timestamps beyond 2038-01-19 03:14:07Z. + config BR2_TARGET_ROOTFS_EXT2_RESBLKS int "reserved blocks percentage" default 5 diff --git a/fs/ext2/ext2.mk b/fs/ext2/ext2.mk index 5b5393f092..e69e79cd2e 100644 --- a/fs/ext2/ext2.mk +++ b/fs/ext2/ext2.mk @@ -22,6 +22,7 @@ ROOTFS_EXT2_OPTS = \ -N $(BR2_TARGET_ROOTFS_EXT2_INODES) \ -m $(BR2_TARGET_ROOTFS_EXT2_RESBLKS) \ -L "$(ROOTFS_EXT2_LABEL)" \ + -I $(BR2_TARGET_ROOTFS_EXT2_INODE_SIZE) \ $(ROOTFS_EXT2_MKFS_OPTS) ROOTFS_EXT2_DEPENDENCIES = host-e2fsprogs