On Tue, Jul 14, 2015 at 04:34:48PM +0100, fdman...@kernel.org wrote: > From: Filipe Manana <fdman...@suse.com> > > Using the clone ioctl (or extent_same ioctl, which calls the same extent > cloning function as well) we end up allowing copy an inline extent from > the source file into a non-zero offset of the destination file. This is > something not expected and that the btrfs code is not prepared to deal > with - all inline extents must be at a file offset equals to 0. >
Somehow I failed to reproduce the BUG_ON with this case. > For example, the following excerpt of a test case for fstests triggers > a crash/BUG_ON() on a write operation after an inline extent is cloned > into a non-zero offset: > > _scratch_mkfs >>$seqres.full 2>&1 > _scratch_mount > > # Create our test files. File foo has the same 2K of data at offset 4K > # as file bar has at its offset 0. > $XFS_IO_PROG -f -s -c "pwrite -S 0xaa 0 4K" \ > -c "pwrite -S 0xbb 4k 2K" \ > -c "pwrite -S 0xcc 8K 4K" \ > $SCRATCH_MNT/foo | _filter_xfs_io > > # File bar consists of a single inline extent (2K size). > $XFS_IO_PROG -f -s -c "pwrite -S 0xbb 0 2K" \ > $SCRATCH_MNT/bar | _filter_xfs_io > > # Now call the clone ioctl to clone the extent of file bar into file > # foo at its offset 4K. This made file foo have an inline extent at > # offset 4K, something which the btrfs code can not deal with in future > # IO operations because all inline extents are supposed to start at an > # offset of 0, resulting in all sorts of chaos. > # So here we validate that clone ioctl returns an EOPNOTSUPP, which is > # what it returns for other cases dealing with inlined extents. > $CLONER_PROG -s 0 -d $((4 * 1024)) -l $((2 * 1024)) \ > $SCRATCH_MNT/bar $SCRATCH_MNT/foo > > # Because of the inline extent at offset 4K, the following write made > # the kernel crash with a BUG_ON(). > $XFS_IO_PROG -c "pwrite -S 0xdd 6K 2K" $SCRATCH_MNT/foo | _filter_xfs_io > On 4.10, after allowing to clone an inline extent to dst file's offset greater than zero, I followed the test case manually and got these [root@localhost trinity]# /home/btrfs-progs/btrfs-debugfs -f /mnt/btrfs/foo (257 0): ram 4096 disk 12648448 disk_size 4096 (257 4096): ram 2048 disk 0 disk_size 2048 -- inline (257 8192): ram 4096 disk 12656640 disk_size 4096 file: /mnt/btrfs/foo extents 3 disk size 10240 logical size 12288 ratio 1.20 [root@localhost trinity]# xfs_io -f -c "pwrite 6k 2k" /mnt/btrfs/foo wrote 2048/2048 bytes at offset 6144 2 KiB, 1 ops; 0.0000 sec (12.520 MiB/sec and 6410.2564 ops/sec) [root@localhost trinity]# sync [root@localhost trinity]# /home/btrfs-progs/btrfs-debugfs -f /mnt/btrfs/foo (257 0): ram 4096 disk 12648448 disk_size 4096 (257 4096): ram 4096 disk 12582912 disk_size 4096 (257 8192): ram 4096 disk 12656640 disk_size 4096 file: /mnt/btrfs/foo extents 3 disk size 12288 logical size 12288 ratio 1.00 Looks like we now are able to cope with these inline extents? Thanks, -liubo > status=0 > exit > > The stack trace of the BUG_ON() triggered by the last write is: > > [152154.035903] ------------[ cut here ]------------ > [152154.036424] kernel BUG at mm/page-writeback.c:2286! > [152154.036424] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC > [152154.036424] Modules linked in: btrfs dm_flakey dm_mod crc32c_generic > xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache > sunrpc loop fuse parport_pc acpi_cpu$ > [152154.036424] CPU: 2 PID: 17873 Comm: xfs_io Tainted: G W > 4.1.0-rc6-btrfs-next-11+ #2 > [152154.036424] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014 > [152154.036424] task: ffff880429f70990 ti: ffff880429efc000 task.ti: > ffff880429efc000 > [152154.036424] RIP: 0010:[<ffffffff8111a9d5>] [<ffffffff8111a9d5>] > clear_page_dirty_for_io+0x1e/0x90 > [152154.036424] RSP: 0018:ffff880429effc68 EFLAGS: 00010246 > [152154.036424] RAX: 0200000000000806 RBX: ffffea0006a6d8f0 RCX: > 0000000000000001 > [152154.036424] RDX: 0000000000000000 RSI: ffffffff81155d1b RDI: > ffffea0006a6d8f0 > [152154.036424] RBP: ffff880429effc78 R08: ffff8801ce389fe0 R09: > 0000000000000001 > [152154.036424] R10: 0000000000002000 R11: ffffffffffffffff R12: > ffff8800200dce68 > [152154.036424] R13: 0000000000000000 R14: ffff8800200dcc88 R15: > ffff8803d5736d80 > [152154.036424] FS: 00007fbf119f6700(0000) GS:ffff88043d280000(0000) > knlGS:0000000000000000 > [152154.036424] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [152154.036424] CR2: 0000000001bdc000 CR3: 00000003aa555000 CR4: > 00000000000006e0 > [152154.036424] Stack: > [152154.036424] ffff8803d5736d80 0000000000000001 ffff880429effcd8 > ffffffffa04e97c1 > [152154.036424] ffff880429effd68 ffff880429effd60 0000000000000001 > ffff8800200dc9c8 > [152154.036424] 0000000000000001 ffff8800200dcc88 0000000000000000 > 0000000000001000 > [152154.036424] Call Trace: > [152154.036424] [<ffffffffa04e97c1>] > lock_and_cleanup_extent_if_need+0x147/0x18d [btrfs] > [152154.036424] [<ffffffffa04ea82c>] __btrfs_buffered_write+0x245/0x4c8 > [btrfs] > [152154.036424] [<ffffffffa04ed14b>] ? btrfs_file_write_iter+0x150/0x3e0 > [btrfs] > [152154.036424] [<ffffffffa04ed15a>] ? btrfs_file_write_iter+0x15f/0x3e0 > [btrfs] > [152154.036424] [<ffffffffa04ed2c7>] btrfs_file_write_iter+0x2cc/0x3e0 > [btrfs] > [152154.036424] [<ffffffff81165a4a>] __vfs_write+0x7c/0xa5 > [152154.036424] [<ffffffff81165f89>] vfs_write+0xa0/0xe4 > [152154.036424] [<ffffffff81166855>] SyS_pwrite64+0x64/0x82 > [152154.036424] [<ffffffff81465197>] system_call_fastpath+0x12/0x6f > [152154.036424] Code: 48 89 c7 e8 0f ff ff ff 5b 41 5c 5d c3 0f 1f 44 00 00 > 55 48 89 e5 41 54 53 48 89 fb e8 ae ef 00 00 49 89 c4 48 8b 03 a8 01 75 02 > <0f> 0b 4d 85 e4 74 59 49 8b 3c 2$ > [152154.036424] RIP [<ffffffff8111a9d5>] clear_page_dirty_for_io+0x1e/0x90 > [152154.036424] RSP <ffff880429effc68> > [152154.242621] ---[ end trace e3d3376b23a57041 ]--- > > Fix this by returning the error EOPNOTSUPP if an attempt to copy an > inline extent into a non-zero offset happens, just like what is done for > other scenarios that would require copying/splitting inline extents, > which were introduced by the following commits: > > 00fdf13a2e9f ("Btrfs: fix a crash of clone with inline extents's split") > 3f9e3df8da3c ("btrfs: replace error code from btrfs_drop_extents") > > Cc: sta...@vger.kernel.org > Signed-off-by: Filipe Manana <fdman...@suse.com> > --- > fs/btrfs/ioctl.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c > index d389815..0770c91 100644 > --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -3588,6 +3588,20 @@ process_slot: > u64 trim = 0; > u64 aligned_end = 0; > > + /* > + * Don't copy an inline extent into an offset > + * greater than zero. Having an inline extent > + * at such an offset results in chaos as btrfs > + * isn't prepared for such cases. Just skip > + * this case for the same reasons as commented > + * at btrfs_ioctl_clone(). > + */ > + if (last_dest_end > 0) { > + ret = -EOPNOTSUPP; > + btrfs_end_transaction(trans, root); > + goto out; > + } > + > if (off > key.offset) { > skip = off - key.offset; > new_key.offset += skip; > -- > 2.1.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html