Design and Implementation of the FreeBSD Operating System, The, 2/e

Author:Marshall Kirk McKusick & George V. Neville-Neil & Robert N.M. Watson [McKusick, Marshall Kirk]
Language: eng
Format: epub
Publisher: Addison-Wesley Professional
Published: 2014-09-05T04:00:00+00:00

New Filesystem Capabilities

Several other improvements were made when the enlarged inode format was created. We decided to get an early jump on the year 2038 problem when the 32-bit time fields overflow (specifically, Tue Jan 19 03:14:08 2038 GMT, which could be a really ugly way to usher in the first author’s 84th birthday). We expanded the time fields (which hold seconds-since-1970) for access, modification, and inodemodification times from 32 bits to 64 bits. At plus or minus 136 billion years, this expansion should carry us from well before the universe was created until long after our sun has burned itself out. We left the nanoseconds fields for these times at 32 bits because we did not feel that added resolution was going to be useful in the foreseeable future. We considered expanding the time to only 48 bits. We chose to go to 64 bits, since 64 bits is a native size that can be easily manipulated with existing and likely future architectures. Using 48 bits would have required an extra unpacking or packing step each time the field was read or written. Also, going to 64 bits ensures enough bits for all likely measured time so it will not have to be enlarged.

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