From: Markus Rechberger <Markus.Rechberger@xxxxxxx> Taken from http://bugzilla.kernel.org/show_bug.cgi?id=5079 signed long ranges from -2.147.483.648 to 2.147.483.647 on x86 32bit 10000011110110100100111110111101 .. -2,082,844,739 10000011110110100100111110111101 .. 2,212,122,557 <- this currently gets stored on the disk but when converting it to a 64bit signed long value it loses its sign and becomes positive. Cc: Andreas Dilger <adilger@xxxxxxxxx> Cc: <linux-ext4@xxxxxxxxxxxxxxx> Andreas says: This patch is now treating timestamps with the high bit set as negative times (before Jan 1, 1970). This means we lose 1/2 of the possible range of timestamps (lopping off 68 years before unix timestamp overflow - now only 30 years away :-) to handle the extremely rare case of setting timestamps into the distant past. If we are only interested in fixing the underflow case, we could just limit the values to 0 instead of storing negative values. At worst this will skew the timestamp by a few hours for timezones in the far east (files would still show Jan 1, 1970 in "ls -l" output). That said, it seems 32-bit systems (mine at least) allow files to be set into the past (01/01/1907 works fine) so it seems this patch is bringing the x86_64 behaviour into sync with other kernels. On the plus side, we have a patch that is ready to add nanosecond timestamps to ext3 and as an added bonus adds 2 high bits to the on-disk timestamp so this extends the maximum date to 2242. Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/ext2/inode.c | 6 +++--- fs/ext3/inode.c | 6 +++--- fs/ext4/inode.c | 6 +++--- 3 files changed, 9 insertions(+), 9 deletions(-) diff -puN fs/ext2/inode.c~ext2-3-4-fix-file-date-underflow-on-ext2-3-filesystems-on-64-bit-systems fs/ext2/inode.c --- a/fs/ext2/inode.c~ext2-3-4-fix-file-date-underflow-on-ext2-3-filesystems-on-64-bit-systems +++ a/fs/ext2/inode.c @@ -1079,9 +1079,9 @@ void ext2_read_inode (struct inode * ino } inode->i_nlink = le16_to_cpu(raw_inode->i_links_count); inode->i_size = le32_to_cpu(raw_inode->i_size); - inode->i_atime.tv_sec = le32_to_cpu(raw_inode->i_atime); - inode->i_ctime.tv_sec = le32_to_cpu(raw_inode->i_ctime); - inode->i_mtime.tv_sec = le32_to_cpu(raw_inode->i_mtime); + inode->i_atime.tv_sec = (signed)le32_to_cpu(raw_inode->i_atime); + inode->i_ctime.tv_sec = (signed)le32_to_cpu(raw_inode->i_ctime); + inode->i_mtime.tv_sec = (signed)le32_to_cpu(raw_inode->i_mtime); inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0; ei->i_dtime = le32_to_cpu(raw_inode->i_dtime); /* We now have enough fields to check if the inode was active or not. diff -puN fs/ext3/inode.c~ext2-3-4-fix-file-date-underflow-on-ext2-3-filesystems-on-64-bit-systems fs/ext3/inode.c --- a/fs/ext3/inode.c~ext2-3-4-fix-file-date-underflow-on-ext2-3-filesystems-on-64-bit-systems +++ a/fs/ext3/inode.c @@ -2608,9 +2608,9 @@ void ext3_read_inode(struct inode * inod } inode->i_nlink = le16_to_cpu(raw_inode->i_links_count); inode->i_size = le32_to_cpu(raw_inode->i_size); - inode->i_atime.tv_sec = le32_to_cpu(raw_inode->i_atime); - inode->i_ctime.tv_sec = le32_to_cpu(raw_inode->i_ctime); - inode->i_mtime.tv_sec = le32_to_cpu(raw_inode->i_mtime); + inode->i_atime.tv_sec = (signed)le32_to_cpu(raw_inode->i_atime); + inode->i_ctime.tv_sec = (signed)le32_to_cpu(raw_inode->i_ctime); + inode->i_mtime.tv_sec = (signed)le32_to_cpu(raw_inode->i_mtime); inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec = inode->i_mtime.tv_nsec = 0; ei->i_state = 0; diff -puN fs/ext4/inode.c~ext2-3-4-fix-file-date-underflow-on-ext2-3-filesystems-on-64-bit-systems fs/ext4/inode.c --- a/fs/ext4/inode.c~ext2-3-4-fix-file-date-underflow-on-ext2-3-filesystems-on-64-bit-systems +++ a/fs/ext4/inode.c @@ -2611,9 +2611,9 @@ void ext4_read_inode(struct inode * inod } inode->i_nlink = le16_to_cpu(raw_inode->i_links_count); inode->i_size = le32_to_cpu(raw_inode->i_size); - inode->i_atime.tv_sec = le32_to_cpu(raw_inode->i_atime); - inode->i_ctime.tv_sec = le32_to_cpu(raw_inode->i_ctime); - inode->i_mtime.tv_sec = le32_to_cpu(raw_inode->i_mtime); + inode->i_atime.tv_sec = (signed)le32_to_cpu(raw_inode->i_atime); + inode->i_ctime.tv_sec = (signed)le32_to_cpu(raw_inode->i_ctime); + inode->i_mtime.tv_sec = (signed)le32_to_cpu(raw_inode->i_mtime); inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec = inode->i_mtime.tv_nsec = 0; ei->i_state = 0; _ - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
