Jim Meyering wrote: > Pádraig Brady wrote: >> On 02/04/11 12:16, Jim Meyering wrote: >>> Hi Pádraig, >>> As of this change, >>> >>> copy: with fiemap copy, only sync when needed >>> http://git.savannah.gnu.org/cgit/coreutils.git/commit/?id=f69876e55 >>> >>> fiemap copy with extents beyond EOF can fail on ext4 even with >>> Fedora 15 (2.6.38) and rawhide's 2.6.39 kernel. >>> >>> Here we construct an odd file. First, preallocate 10MB of space, >>> and then write 5KiB of random data into the beginning of that: >>> >>> $ fallocate -l 10000000 -n k >>> $ dd count=10 if=/dev/urandom conv=notrunc iflag=fullblock of=k >>> >>> However, when we try to copy "k", we get a file, "k2" of the >>> expected size, but with only NUL bytes for contents: >> >> So the extent info is not updated until sync(), >> which means cp will consider the "unwritten" extent >> as NUL data and not bother to read it :( >> >> I guess this is a corner case that was missed >> in the fixups for ext4 (and btrfs?) in 2.6.38 for this? >> I've copied ext4 devs for clarification. >> I.E. if you do this: >> >> fallocate -l 10000000 -n k >> dd count=10 if=/dev/urandom conv=notrunc iflag=fullblock of=k >> filefrag -v k >> >> Do you get all extents still unwritten. >> I do on my 2.6.35.11-83.fc14.i686 kernel, but I expected that. > > Right. The new extent remains unwritten until after a sync > with ext4 on both Fedora 15 and rawhide kernels. Here's the quick band-aid I'll push tomorrow. I'll welcome a better fix, but this, at least, lets "make check" pass once again. >From 0a6d128d0d17c1604245f1caafe6af73584a0bb8 Mon Sep 17 00:00:00 2001 From: Jim Meyering <meyering@xxxxxxxxxx> Date: Sat, 2 Apr 2011 19:59:30 +0200 Subject: [PATCH] copy: require fiemap sync also for 2.6.38 and 2.6.39 kernels * src/extent-scan.c (extent_need_sync): Require sync also for 2.6.38 and 2.6.39. Without this, part of the cp/fiemap-empty test would fail both on F15-to-be and rawhide. For discussion and details, see: http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/22190 --- src/extent-scan.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/src/extent-scan.c b/src/extent-scan.c index 4ddf46e..752de85 100644 --- a/src/extent-scan.c +++ b/src/extent-scan.c @@ -31,7 +31,7 @@ # include "fiemap.h" #endif -/* Work around Linux kernel issues on BTRFS and EXT4 before 2.6.38. +/* Work around Linux kernel issues on BTRFS and EXT4 before 2.6.40. FIXME: remove in 2013, or whenever we're pretty confident that the offending, unpatched kernels are no longer in use. */ static bool @@ -50,7 +50,7 @@ extent_need_sync (void) unsigned long val; if (xstrtoul (name.release + 4, NULL, 10, &val, NULL) == LONGINT_OK) { - if (val < 38) + if (val < 40) need_sync = 1; } } -- 1.7.4.2.662.gcbd0 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
