[Bug 10925] non-atomic xattr replacement in btrfs => rsync --read-batch random errors

[samba-bugs at samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=10925

--- Comment #1 from roland <devzero at web.de> ---
interesting find, if btrfs has xattr races, but the question is how to produce
an appropriate repro case.

on a tiny btrfs here on my debian wheezy system, i did some massive parallel
run of 

"setfattr -h -n user.myattr -v attrval dir" in one window, 
whereas doing
getfattr -h -n user.myattr dir  in another window, 

and would have expected to seem some errors. i didn`t. as this is the default
kernel, maybe the race is being introduced in a later version.

furthermore - what specific problem (security or whatever) do you see here with
rsync, if there is a race window between setting and reading an xattr (which
seems is not to be expected behaviour of a filesystem) ?

also see:
https://btrfs.wiki.kernel.org/index.php/Main_Page
If you have any bug, problems, performance issues or questions while using
Btrfs, please email the Btrfs mailing list (no subscription required). Please
report bugs also on Bugzilla.

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