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SubjectRe: truncate and {m,c}time on ntfs
On Sun, 12 Mar 2006, Anton Altaparmakov wrote:
> Hi Christoph,
>
> A patch of yours modified fs/ntfs/inode.c::ntfs_truncate() and inserted
> this comment:
>
> [snip]
> /* normally ->truncate shouldn't update ctime or mtime,
> * but ntfs did before so it got a copy & paste version
> * of file_update_time. one day someone should fix this
> * for real.
> */
> [snip]
>
> Did you realise that all (local) file systems in Linux kernel set both
> {m,c}time in their ->truncate function. E.g. from
> fs/ext3.c/inode.c::ext3_truncate():
>
> inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
>
> Would you be so kind to explain what is your problem with ntfs doing it,
> too? And if your statement is correct and no file system should touch
> {m,c}time in their ->truncate() method, could you explain to me how the
> {m,c}time would be set otherwise when open(O_TRUNC) or {f,}truncate() is
> executed on a file?

Sorry, I know how open(O_TRUNC) sets it as it calls do_truncate(,,
ATTR_MTIME|ATTR_CTIME,) but at present both {f,}truncate() call
do_truncate(,, 0,) and I do not see anywhere else where the setting
would/could be done, other than in the file system ->truncate method.

In fact if I take the setting of {m,c}time out of ntfs_truncate(), doing:

touch
stat foo
truncate foo 10
stat foo

Does not result in a change in the {m,c}time...

Given posix/sus3 requires setting of {m,c}time on truncate, it would
appear that a file system ->truncate function needs to set {m,c}time
itself...

Please explain why you added your comment to ntfs...

Thanks a lot in advance.

Best regards,

Anton
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/
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