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Qu Wenruo
6df776bae8
For fully deduped file, which means all its file exntents are pointing to the same bytenr, btrfs can cause soft lockup when calling fiemap ioctl on that file, like the following output: ------ CPU: 1 PID: 7500 Comm: xfs_io Not tainted 4.5.0-rc6+ #2 Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 task: ffff880027681b40 ti: ffff8800276e0000 task.ti: ffff8800276e0000 RIP: 0010:[<ffffffffa02583e4>] [<ffffffffa02583e4>] __merge_refs+0x34/0x120 [btrfs] RSP: 0018:ffff8800276e3c08 EFLAGS: 00000202 RAX: ffff8800269cc330 RBX: ffff8800269cdb18 RCX: 0000000000000007 RDX: 00000000000061b0 RSI: ffff8800269cc4c8 RDI: ffff8800276e3c88 RBP: ffff8800276e3c20 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000000 R12: ffff880026ea3cb0 R13: ffff8800276e3c88 R14: ffff880027132a50 R15: ffff880027430000 FS: 00007f10201df700(0000) GS:ffff88003fa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f10201ec000 CR3: 0000000027603000 CR4: 00000000000406e0 Stack: 0000000000000000 0000000000000000 0000000000000000 ffff8800276e3ce8 ffffffffa0259f38 0000000000000005 ffff8800274c6870 ffff8800274c7d88 0000000000c10000 0000000000000000 0000000000000001 0000000027431190 Call Trace: [<ffffffffa0259f38>] find_parent_nodes+0x448/0x740 [btrfs] [<ffffffffa025a4f2>] btrfs_check_shared+0x102/0x1b0 [btrfs] [<ffffffff811fdcad>] ? __might_fault+0x4d/0xa0 [<ffffffffa021899c>] extent_fiemap+0x2ac/0x550 [btrfs] [<ffffffff811ce156>] ? __filemap_fdatawait_range+0x96/0x160 [<ffffffffa01f8ee0>] ? btrfs_get_extent+0xb30/0xb30 [btrfs] [<ffffffffa01f5da5>] btrfs_fiemap+0x45/0x50 [btrfs] [<ffffffff81246bb8>] do_vfs_ioctl+0x498/0x670 [<ffffffff81246e09>] SyS_ioctl+0x79/0x90 [<ffffffff8184e997>] entry_SYSCALL_64_fastpath+0x12/0x6f Code: 41 55 41 54 53 4c 8b 27 4c 39 e7 0f 84 e9 00 00 00 49 89 fd 49 8b 34 24 49 39 f5 48 8b 1e 75 17 e9 d5 00 00 00 49 39 dd 48 8b 03 <48> 89 de 0f 84 b9 00 00 00 48 89 c3 8b 46 2c 41 39 44 24 2c 75 ------ Also btrfs will return wrong flag for all these extents, they should have SHARED(0x2000) flags, while btrfs still consider them as exclusive extents. On the other hand, with unmerged xfs reflink patches, xfs can handle it without problem, and for patched btrfs, it can also handle it. This test case will create a large fully deduped file to check if the fs can handle the fiemap ioctl and return correct SHARED flag for any fs which support reflink. Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Reviewed-by: Eryu Guan <eguan@redhat.com> Signed-off-by: Eryu Guan <eguan@redhat.com>