Re: [PATCH][RFC][BUG] updating the ctime and mtime time stamps in msync()

Valdis.Kletnieks
2008-01-09T21:06:49Z

[-- Attachment #1: Type: text/plain, Size: 940 bytes --]

On Wed, 09 Jan 2008 15:50:15 EST, Rik van Riel said:

> Could you explain (using short words and simple sentences) what the
> exact problem is?
>
> Eg.
>
> 1) program mmaps file
> 2) program writes to mmaped area
> 3) ??? <=== this part, in equally simple words :)
> 4) data loss

It's like this:

Monday 9:04AM: System boots, database server starts up, mmaps file
Monday 9:06AM: Database server writes to mmap area, updates mtime/ctime
Monday <many times> Database server writes to mmap area, no further update..
Monday 11:45PM: Backup sees "file modified 9:06AM, let's back it up"
Tuesday 9:00AM-5:00PM: Database server touches it another 5,398 times, no mtime
Tuesday 11:45PM: Backup sees "file modified back on Monday, we backed this up..
Wed 9:00AM-5:00PM: More updates, more not touching the mtime
Wed 11:45PM: *yawn* It hasn't been touched in 2 days, no sense in backing it up..

Lather, rinse, repeat....

[-- Attachment #2: Type: application/pgp-signature, Size: 226 bytes --]