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Subject[PATCH v8 09/20] ext4: Initialize timestamps limits
Date
ext4 has different overflow limits for max filesystem
timestamps based on the extra bytes available.

The timestamp limits are calculated according to the
encoding table in
a4dad1ae24f85i(ext4: Fix handling of extended tv_sec):

* extra msb of adjust for signed
* epoch 32-bit 32-bit tv_sec to
* bits time decoded 64-bit tv_sec 64-bit tv_sec valid time range
* 0 0 1 -0x80000000..-0x00000001 0x000000000 1901-12-13..1969-12-31
* 0 0 0 0x000000000..0x07fffffff 0x000000000 1970-01-01..2038-01-19
* 0 1 1 0x080000000..0x0ffffffff 0x100000000 2038-01-19..2106-02-07
* 0 1 0 0x100000000..0x17fffffff 0x100000000 2106-02-07..2174-02-25
* 1 0 1 0x180000000..0x1ffffffff 0x200000000 2174-02-25..2242-03-16
* 1 0 0 0x200000000..0x27fffffff 0x200000000 2242-03-16..2310-04-04
* 1 1 1 0x280000000..0x2ffffffff 0x300000000 2310-04-04..2378-04-22
* 1 1 0 0x300000000..0x37fffffff 0x300000000 2378-04-22..2446-05-10

Note that the time limits are not correct for deletion times.

Added a warn when an inode cannot be extended to incorporate an
extended timestamp.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Cc: tytso@mit.edu
Cc: adilger.kernel@dilger.ca
Cc: linux-ext4@vger.kernel.org
---
fs/ext4/ext4.h | 10 +++++++++-
fs/ext4/super.c | 17 +++++++++++++++--
2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9c7f4036021b..ae5d0c86aba2 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -832,11 +832,15 @@ static inline void ext4_decode_extra_time(struct timespec64 *time,

#define EXT4_INODE_SET_XTIME(xtime, inode, raw_inode) \
do { \
- (raw_inode)->xtime = cpu_to_le32((inode)->xtime.tv_sec); \
if (EXT4_FITS_IN_INODE(raw_inode, EXT4_I(inode), xtime ## _extra)) {\
+ (raw_inode)->xtime = cpu_to_le32((inode)->xtime.tv_sec); \
(raw_inode)->xtime ## _extra = \
ext4_encode_extra_time(&(inode)->xtime); \
} \
+ else {\
+ (raw_inode)->xtime = cpu_to_le32(clamp_t(int32_t, (inode)->xtime.tv_sec, S32_MIN, S32_MAX)); \
+ ext4_warning_inode(inode, "inode does not support timestamps beyond 2038"); \
+ } \
} while (0)

#define EXT4_EINODE_SET_XTIME(xtime, einode, raw_inode) \
@@ -1643,6 +1647,10 @@ static inline bool ext4_verity_in_progress(struct inode *inode)

#define EXT4_GOOD_OLD_INODE_SIZE 128

+#define EXT4_EXTRA_TIMESTAMP_MAX (((s64)1 << 34) - 1 + S32_MIN)
+#define EXT4_NON_EXTRA_TIMESTAMP_MAX S32_MAX
+#define EXT4_TIMESTAMP_MIN S32_MIN
+
/*
* Feature set definitions
*/
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 27cd622676e7..3db5f17228b7 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4039,8 +4039,21 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
sbi->s_inode_size);
goto failed_mount;
}
- if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE)
- sb->s_time_gran = 1 << (EXT4_EPOCH_BITS - 2);
+ /*
+ * i_atime_extra is the last extra field available for [acm]times in
+ * struct ext4_inode. Checking for that field should suffice to ensure
+ * we have extra space for all three.
+ */
+ if (sbi->s_inode_size >= offsetof(struct ext4_inode, i_atime_extra) +
+ sizeof(((struct ext4_inode *)0)->i_atime_extra)) {
+ sb->s_time_gran = 1;
+ sb->s_time_max = EXT4_EXTRA_TIMESTAMP_MAX;
+ } else {
+ sb->s_time_gran = NSEC_PER_SEC;
+ sb->s_time_max = EXT4_NON_EXTRA_TIMESTAMP_MAX;
+ }
+
+ sb->s_time_min = EXT4_TIMESTAMP_MIN;
}

sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
--
2.17.1
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