On 12/5/16 9:19 AM, Amir Goldstein wrote: > On Mon, Dec 5, 2016 at 4:19 PM, Eric Sandeen <sandeen@xxxxxxxxxxx> wrote: >> On 12/5/16 7:03 AM, Amir Goldstein wrote: >>> There is an undocumented and possibly unused feature in xfs_io >>> where all commands are executed per file in the file args list. >>> >>> This feature creates ambiguity when trying to execute commands >>> such as "open" and "file" from command line and result in an >>> endless loop in the command loop code. >> >> I may well be dense, but it's not immediately obvious what the >> old and/or problematic behavior is. Can you spell it out a bit >> more? What is an example of this loop? > > $ touch foo > $ xfs_io -c "open foo" foo > > you will see the shit storm ;) Ok thanks. (would be nice to have that in the changelog) > >> >>> Also, when running xfs_io -c <cmd> without any file args, xfs_io >>> exits without doing anything. This behavior is also undocumented >>> and makes very little sense. >> >> What /should/ it do if there is no file specified? Is this just for >> cmds that don't require a file, such as "-c sync?" > > Execute the commands as if you ran xfs_io and entered those commands > in the shell, for example: > > $ xfs_io -c "open foo" -c "pread -v 0 4" ok, I see. >> >>> Change the behavior of xfs_io to execute each command specified >>> with -c <cmd> exactly once, regardless of the number of files in >>> the file args list. >> >> So then which file does it act on? I'm not saying this is incorrect, >> I'm just not quite understanding what this fixes, and what the new >> behavior is, sorry. >> > > You are not to be blamed for not knowing what the old behavior is > it is undocumented and I have never seen it used in tests. > > Old behavior of > > $ xfs_io -c -c "pread -v 0 4" -c "pread -v 4 8" foo bar > > - print 0..4 from foo > - print 4..8 from foo > - print 0..4 from bar > - print 4..8 from bar Ok, interesting. yeah, the manpage does not even say more than one file arg is allowed. > New behavior is: > > - print 0..4 from bar (the "current" file) > - print 4..8 from bar > > Same behavior as when you issue the same command after running > > $ xfs_io foo bar Given that neither the manpage nor the short help mention that more than one filename is accepted, should this even succeed at all? If it does succeed, and has a known behavior, and its desirable, then this warrants a documentation update as well. And then probably an xfstests test case to be sure it doesn't drift. ;) -Eric > Amir. > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
