bug#6131: [PATCH]: fiemap support for efficient sparse file copy (original) (raw)

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From: Jim Meyering
Subject: bug#6131: [PATCH]: fiemap support for efficient sparse file copy
Date: Thu, 27 May 2010 20:45:24 +0200

jeff.liu wrote:

Jim Meyering wrote: > jeff.liu wrote: >> This is the revised version, it fixed the fiemap-start offset calculation >> approach to remove it out >> of the 'for (i = 0; i < fiemap->fmmappedextents; i++)' loop. > > Hi Jeff, > > I've included below the state of my local changes. > Unfortunately, with that 5-patch series, there is always a test failure > on F13/ext4. Maybe someone who knows more about extents can provide an > explanation? > > Here's a small example to demonstrate: > > Create a file with many extents: > _> perl -e 'BEGIN { $n = 19 * 1024; *F = *STDOUT }' _ _> -e 'for (1..100) { sysseek (*F, $n, 1)' _ > -e '&& syswrite (*F, "."x$n) or die "$!"}' > j1 > > Using the patched "cp", repeat the following 10 or 20 times: > > ./cp --sparse=always j1 j2; sync > filefrag -v j1 | awk '/^ / {print 1,1,1,2}' > ff1 || fail=1 > filefrag -v j2 | awk '/^ / {print 1,1,1,2}' > ff2 || fail=1 > diff -u ff1 ff2 || fail=1 > > Usually there is no diff output, but occasionally it'll print this: > [hmm... today it consistently prints these differences every other time.] Woo!!! I just run this test on btrfs/ext4/ocfs2 against mainline kernel(Linux jeff-laptop 2.6.33-rc5-00238-gb04da8b-dirty) on my laptop. Only btrfs always works well for me, Ext4 has the same issue like yours.

One more point of reference: the tests all passed on an XFS file system.