[Ocfs2-devel] FIEMAP problem
David Weber
wb at munzinger.de
Tue Aug 27 01:18:21 PDT 2013
Am Donnerstag, 8. August 2013, 09:20:45 schrieb Sunil Mushran:
> So it's a test issue. The utility assumes the fs allocates in 4K units.
> That's why it only works when clustersize is 4K.
Thanks for the clarification!
The patch seems to have solved our problem. It would be great if it could be
pushed to Linux.
Cheers,
David
>
> On Thu, Aug 8, 2013 at 8:09 AM, David Weber <wb at munzinger.de> wrote:
> > Am Donnerstag, 8. August 2013, 07:30:27 schrieb Sunil Mushran:
> > > Interesting. Please can you print the inode disk using the command
> > > below.
> > > The file path is minus the mounted dir.
> > >
> > > debugfs.ocfs2 -R "stat /relative/path/to/file" /dev/DEVICE
> > >
> > > It is saying that the fs has allocated a block when it did not need to.
> >
> > It
> >
> > > could be that the test utility does not handle blocks larger than 4K, or
> > > the fiemap ioctl has a bug or the fs is indeed allocating a block when
> > > it
> > > does not need to. The above command will show us the actual layout on
> >
> > disk.
> >
> > Thank you for looking into this!
> >
> > # ./fiemap-tester /mnt/kvm-images/fiemap_new
> > Starting infinite run, if you don't see any output then its working
> > properly.
> > HEY FS PERSON: your fs is weird. I specifically wanted a
> > hole and you allocated a block anyway. FIBMAP confirms that
> > you allocated a block, and the block is filled with 0's so
> > everything is kosher, but you still allocated a block when
> > didn't need to. This may or may not be what you wanted,
> > which is why I'm only printing this message once, in case
> > you didn't do it on purpose. This was at block 0.
> > ERROR: preallocated extent is not marked with FIEMAP_EXTENT_UNWRITTEN: 0
> > map is
> >
> > 'HDHPHHDDHPHPHPHDDHHPPDDPPPHHHPDDDPDHHHHDDDPPHPPPDPHHPPDPPHHDDPDPPHDHPDDDD
> > PDPPDPHDDPPDDPPHDDPDHHHDDPDHPHPDPPDDHPHPPHDPHPHDDHDPDPDHDHPDDPHPPPHDPPDPDD
> > HPHDDPPHPDHPPHPPHPHHPHDHPPDDPHDHHPPHPPDHPHPHDHPPDDDDPHHHPPPHHHDDDDPDPDDPPP
> > HPHDPPPHDPDPHDDHPPPDPDHPHHPHDHHDHPDPHDDPPHDPPDDPDDPPDHPPDPDHHPHDHPPHDDHDPH
> > PPPDHPDDDHDDHDPPHHDDPPDPDDHDHHPHDPHHPPPDPPDHDHHPPHDPHDPPHDPHHPPP' logical:
> > [ 0.. 255] phys: 206615552..206615807 flags: 0x000 tot: 256
> > Problem comparing fiemap and map
> >
> > # debugfs.ocfs2 -R "stat /fiemap_new" /dev/drbd0
> >
> > Inode: 92668161 Mode: 0644 Generation: 3713753505 (0xdd5b61a1)
> > FS Generation: 2357962590 (0x8c8ba75e)
> > CRC32: 00000000 ECC: 0000
> > Type: Regular Attr: 0x0 Flags: Valid
> > Dynamic Features: (0x0)
> > User: 0 (root) Group: 0 (root) Size: 1470464
> > Links: 1 Clusters: 2
> > ctime: 0x5203b200 0x991cd -- Thu Aug 8 16:58:08.627149 2013
> > atime: 0x5203b200 0xc0accc -- Thu Aug 8 16:58:08.12627148 2013
> > mtime: 0x5203b200 0x991cd -- Thu Aug 8 16:58:08.627149 2013
> > dtime: 0x0 -- Thu Jan 1 01:00:00 1970
> > Refcount Block: 0
> > Last Extblk: 0 Orphan Slot: 0
> > Sub Alloc Slot: 0 Sub Alloc Bit: 1
> > Tree Depth: 0 Count: 243 Next Free Rec: 2
> > ## Offset Clusters Block# Flags
> > 0 0 1 206615552 0x0
> > 1 1 1 206619648 0x0
> > >
> > > On Aug 8, 2013, at 2:16 AM, David Weber <wb at munzinger.de> wrote:
> > > > Am Mittwoch, 7. August 2013, 22:07:19 schrieb Jeff Liu:
> > > >> On 08/07/2013 05:17 PM, David Weber wrote:
> > > >>> Hi,
> > > >>>
> > > >>> We are trying to use OCFS2 as VM storage. After running into
> > > >>> problems
> > > >>> with
> > > >>> qemu's disk_mirror feature we now think there could be a problem
> > > >>> with
> > > >>> the
> > > >>> FIEMAP ioctl in OCFS2.
> > > >>>
> > > >>> As far as I understand the situation looks like this:
> > > >>> Qemu inquiries the FS if the given section of the image is already
> > > >>> allocated via the FIEMAP ioctl [1]
> > > >>> It especially checks if fm_mapped_extents is greater 0.
> > > >>> OCFS2 reports on sections bigger 1048576 there would be 0
> >
> > mapped_extents
> >
> > > >>> which is wrong.
> > > >>>
> > > >>> I extended a userspace FIEMAP util [2] a bit to specify the start
> > > >>> and
> > > >>> length parameter [3] as an easier testcase.
> > > >>>
> > > >>> When we create a big file which has no holes
> > > >>> dd if=/dev/urandom of=/mnt/kvm-images/urandom.img bs=1M count=1000
> > > >>>
> > > >>> We get on lower sections the expected output:
> > > >>> ./a.out /mnt/kvm-images/urandom.img 10000 10
> > > >>> start: 2710, length: a
> > > >>> File /mnt/kvm-images/urandom.img has 1 extents:
> > > >>> # Logical Physical Length Flags
> > > >>> 0: 0000000000000000 0000004ca3f00000 000000000be00000 0000
> > > >>>
> > > >>> But on sections >= 1048576 it reports there wouldn't be any extents
> > > >>> which
> > > >>> is as far as I understand wrong:
> > > >>> ./a.out /mnt/kvm-images/urandom.img 1048576 10
> > > >>> start: 100000, length: a
> > > >>> File /mnt/kvm-images/urandom.img has 0 extents:
> > > >>> # Logical Physical Length Flags
> > > >>
> > > >> Thanks for your report, looks this problem has existed over years.
> > > >> As a quick response, could you please try the below fix?
> > > >
> > > > Thank you very much! This solved the problems with qemu.
> > > >
> > > > I found a fiemap-tester util[1] in the xfstests project and it runs
> >
> > fine
> >
> > > > on
> > > > OCFS2 with 4K cluster size but fails with 1M. I have however no idea
> > > > if
> > > > this is a severe problem.
> > > >
> > > > # gcc -DHAVE_FALLOCATE=1 -o fiemap-tester fiemap-tester.c
> > > > # ./fiemap-tester /mnt/kvm-images/fiemap_test
> > > > Starting infinite run, if you don't see any output then its working
> > > > properly. HEY FS PERSON: your fs is weird. I specifically wanted a
> > > > hole and you allocated a block anyway. FIBMAP confirms that
> > > > you allocated a block, and the block is filled with 0's so
> > > > everything is kosher, but you still allocated a block when
> > > > didn't need to. This may or may not be what you wanted,
> > > > which is why I'm only printing this message once, in case
> > > > you didn't do it on purpose. This was at block 0.
> >
> > > > ERROR: preallocated extent is not marked with FIEMAP_EXTENT_UNWRITTEN:
> > 0
> >
> > > > map is
> >
> > 'HDHPHHDDHPHPHPHDDHHPPDDPPPHHHPDDDPDHHHHDDDPPHPPPDPHHPPDPPHHDDPDPPHDHPDDDD
> >
> > PDPPDPHDDPPDDPPHDDPDHHHDDPDHPHPDPPDDHPHPPHDPHPHDDHDPDPDHDHPDDPHPPPHDPPDPDD
> >
> > HPHDDPPHPDHPPHPPHPHHPHDHPPDDPHDHHPPHPPDHPHPHDHPPDDDDPHHHPPPHHHDDDDPDPDDPPP
> >
> > HPHDPPPHDPDPHDDHPPPDPDHPHHPHDHHDHPDPHDDPPHDPPDDPDDPPDHPPDPDHHPHDHPPHDDHDPH
> >
> > > > PPPDHPDDDHDDHDPPHHDDPPDPDDHDHHPHDPHHPPPDPPDHDHHPPHDPHDPPHDPHHPPP'
> >
> > logical:
> > > > [ 0.. 255] phys: 132160512..132160767 flags: 0x000 tot: 256
> > > >
> > > >
> > > > [1]
> >
> > http://oss.sgi.com/cgi-bin/gitweb.cgi?p=xfs/cmds/xfstests.git;a=blob_plai
> >
> > > > n;f=src/fiemap-tester.c;hb=HEAD>
> > > >
> > > >> From: Jie Liu <jeff.liu at oracle.com>
> > > >>
> > > >> Call fiemap ioctl(2) with given start offset as well as an desired
> > > >> mapping range should show extents if possible. However, we calculate
> > > >> the end offset of mapping via 'mapping_end -= cpos' before iterating
> > > >> the extent records which would cause problems, e.g,
> > > >>
> > > >> Cluster size 4096:
> > > >> debugfs.ocfs2 1.6.3
> > > >>
> > > >> Block Size Bits: 12 Cluster Size Bits: 12
> > > >>
> > > >> The extended fiemap test utility From David:
> > > >> https://gist.github.com/anonymous/6172331
> > > >>
> > > >> # dd if=/dev/urandom of=/ocfs2/test_file bs=1M count=1000
> > > >> # ./fiemap /ocfs2/test_file 4096 10
> > > >> start: 4096, length: 10
> > > >> File /ocfs2/test_file has 0 extents:
> > > >> # Logical Physical Length Flags
> > > >>
> > > >> ^^^^^ <-- No extents
> > > >>
> > > >> In this case, at ocfs2_fiemap(): cpos == mapping_end == 1. Hence the
> > > >> loop of searching extent records was not executed at all.
> > > >>
> > > >> This patch remove the in question 'mapping_end -= cpos', and loops
> > > >> until the cpos is larger than the mapping_end instead.
> > > >>
> > > >> # ./fiemap /ocfs2/test_file 4096 10
> > > >> start: 4096, length: 10
> > > >> File /ocfs2/test_file has 1 extents:
> > > >> # Logical Physical Length Flags
> > > >> 0: 0000000000000000 0000000056a01000 0000000006a00000 0000
> > > >>
> > > >> Reported-by: David Weber <wb at munzinger.de>
> > > >> Cc: Mark Fashen <mfasheh at suse.de>
> > > >> Cc: Joel Becker <jlbec at evilplan.org>
> > > >> Signed-off-by: Jie Liu <jeff.liu at oracle.com>
> > > >> ---
> > > >> fs/ocfs2/extent_map.c | 1 -
> > > >> 1 file changed, 1 deletion(-)
> > > >>
> > > >> diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
> > > >> index 2487116..8460647 100644
> > > >> --- a/fs/ocfs2/extent_map.c
> > > >> +++ b/fs/ocfs2/extent_map.c
> > > >> @@ -781,7 +781,6 @@ int ocfs2_fiemap(struct inode *inode, struct
> > > >> fiemap_extent_info *fieinfo, cpos = map_start >>
> >
> > osb->s_clustersize_bits;
> >
> > > >> mapping_end = ocfs2_clusters_for_bytes(inode->i_sb,
> > > >>
> > > >> map_start + map_len);
> > > >>
> > > >> - mapping_end -= cpos;
> > > >>
> > > >> is_last = 0;
> > > >> while (cpos < mapping_end && !is_last) {
> > > >>
> > > >> u32 fe_flags;
> > > >>>
> > > >>> We're running linux-3.11-rc4 plus the following patches:
> > > >>> [PATCH V2] ocfs2: update inode size after zeroed the hole
> > > >>> [PATCH RESEND] ocfs2: fix NULL pointer dereference in
> > > >>> ocfs2_duplicate_clusters_by_page
> > > >>> NULL pointer dereference at ocfs2_dir_foreach_blk_id
> > > >>> [patch v3] ocfs2: ocfs2: fix recent memory corruption bug
> > > >>>
> > > >>> o2info --volinfo /dev/drbd0
> > > >>>
> > > >>> Label: kvm-images
> > > >>>
> > > >>> UUID: BE7C101466AD4F2196A849C7A6031263
> > > >>>
> > > >>> Block Size: 4096
> > > >>>
> > > >>> Cluster Size: 1048576
> > > >>>
> > > >>> Node Slots: 8
> > > >>>
> > > >>> Features: backup-super strict-journal-super sparse
> >
> > extended-slotmap
> >
> > > >>> Features: inline-data xattr indexed-dirs refcount discontig-bg
> > > >>> unwritten
> > > >>>
> > > >>> Thanks in advance!
> > > >>>
> > > >>> Cheers,
> > > >>> David
> > > >>>
> > > >>>
> > > >>> [1]
> >
> > http://git.qemu.org/?p=qemu.git;a=blob;f=block/raw-posix.c;h=ba721d3f5bd
> >
> > > >>> 9
> > > >>> 8a6b62791c2e20dbf2894021ad76;hb=HEAD#l1087
> > > >>>
> > > >>> [2]
> >
> > http://smackerelofopinion.blogspot.de/2010/01/using-fiemap-ioctl-to-get->
> >
> > >>> f
> > >>>
> > > >>> ile-extents.html
> > > >>>
> > > >>> [3] https://gist.github.com/anonymous/6172331
> > > >>>
> > > >>>
> > > >>> _______________________________________________
> > > >>> Ocfs2-devel mailing list
> > > >>> Ocfs2-devel at oss.oracle.com
> > > >>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
> > > >
> > > > _______________________________________________
> > > > Ocfs2-devel mailing list
> > > > Ocfs2-devel at oss.oracle.com
> > > > https://oss.oracle.com/mailman/listinfo/ocfs2-devel
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