On 12/6/17 4:16 PM, Dave Chinner wrote: > On Wed, Dec 06, 2017 at 04:01:58PM -0600, Eric Sandeen wrote: >> On 12/6/17 3:57 PM, Dave Chinner wrote: >> >>> There's a *simple answer* to this problem: fix the new command's >>> output. >>> >>> That is: the user asked for a specific range, so the command itself >>> should trim the map returned by the kernel to only display the exact >>> range the user asked for. Then it doesn't matter if the underlying >>> filesystem trims the extents or not, because the we're going to do >>> that anyway in userspace. >> >> I have a different opinion: >> >> xfs_io is a debugging tool; the fiemap command sends an ioctl to the kernel. >> >> Ranged fiemap queries are a real thing; you put numbers into the kernel, >> and you get numbers out of the kernel. >> >> IMNSO, xfs_io should present to the user /what the kernel returned/, >> and not re-interpret it to fit some other notion of correctness if we >> don't like what the kernel told us. > > I hardly think "trimming to the range the user asked for" is > "re-interpreting what the kernel told us". It's limiting output > range to exactly what the user asked for - the output is still > correct regardless of how it's filtered to match what the user asked > for.... > >> If you want to have some user-friendlier behavior where xfs_io layers >> behaviors on top of what the kernel provides, then add a "-t" argument for trim, >> but hiding ioctl inconsistencies by filtering them through xfs_io sounds >> like the wrong approach to me. > > Just filter the last output in the test, then, so it looks like > > 2: [128..XXX] data Would need to do the same for the first extent AIUI. > There is absolutely no excuse for creating multiple tests to support > a small difference in trailing extent range output from different > filesystem. Excuse #1 is to ensure that for filesystems which return extent data past the requested range, it's actually correct... If we trim/filter it away and it returns junk for any reason, we'd never know via this test. So I think filtering the first/last lengths is a reasonable way to force it into a common test, but it reduces the value of the test to some degree. -Eric -- 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
