Re: Documenting MS_LAZYTIME | linux-api

(off-list ancestor, not in this archive)

On 02/26/2015 02:31 PM, Theodore Ts'o wrote:
On Thu, Feb 26, 2015 at 09:49:39AM +0100, Michael Kerrisk (man-pages) wrote:
How about somethign like "This mount significantly reduces writes
needed to update the inode's timestamps, especially mtime and actime.
What is "actime" in the preceding line? Should it be "ctime"?
Sorry, no, it should be "atime".
Thanks.

I find the wording of there a little confusing. Is the following 
a correct rewrite:

    The advantage of MS_STRICTATIME | MS_LAZYTIME is that stat(2)
    will return the correctly updated atime, but the atime updates
    will be flushed to disk only when (1) the inode needs to be 
    updated for filesystem / data consistency reasons or (2) the 
    inode is pushed out of memory, or (3) the filesystem is 
    unmounted.)
Yes, that's correct.  The only other thing I might add is that in the
case of a crash, the atime (or mtime) fields on disk might be out of
date by at most 24 hours.
So in other words, add a sentence to that last para:

    The disadvantage of MS_STRICTATIME | MS_LAZYTIME is that
    in the case of a system crash, the atime and mtime fields
    on disk might be out of date by at most 24 hours.

Right?

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

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