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ed95876264
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.
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" $SCRATCH_MNT/foo | _filter_xfs_io
status=0
exit
The stack trace of the BUG_ON() triggered by the last write is:
[152154.035903] ------------[ cut here ]------------
[152154.036424] kernel BUG at mm/page-writeback.c:2286!
[152154.036424] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[152154.036424] Modules linked in: btrfs dm_flakey dm_mod crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop fuse parport_pc acpi_cpu$
[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:
|
||
|---|---|---|
| .. | ||
| tests | ||
| acl.c | ||
| async-thread.c | ||
| async-thread.h | ||
| backref.c | ||
| backref.h | ||
| btrfs_inode.h | ||
| check-integrity.c | ||
| check-integrity.h | ||
| compression.c | ||
| compression.h | ||
| ctree.c | ||
| ctree.h | ||
| delayed-inode.c | ||
| delayed-inode.h | ||
| delayed-ref.c | ||
| delayed-ref.h | ||
| dev-replace.c | ||
| dev-replace.h | ||
| dir-item.c | ||
| disk-io.c | ||
| disk-io.h | ||
| export.c | ||
| export.h | ||
| extent-tree.c | ||
| extent-tree.h | ||
| extent_io.c | ||
| extent_io.h | ||
| extent_map.c | ||
| extent_map.h | ||
| file-item.c | ||
| file.c | ||
| free-space-cache.c | ||
| free-space-cache.h | ||
| hash.c | ||
| hash.h | ||
| inode-item.c | ||
| inode-map.c | ||
| inode-map.h | ||
| inode.c | ||
| ioctl.c | ||
| Kconfig | ||
| locking.c | ||
| locking.h | ||
| lzo.c | ||
| Makefile | ||
| math.h | ||
| ordered-data.c | ||
| ordered-data.h | ||
| orphan.c | ||
| print-tree.c | ||
| print-tree.h | ||
| props.c | ||
| props.h | ||
| qgroup.c | ||
| qgroup.h | ||
| raid56.c | ||
| raid56.h | ||
| rcu-string.h | ||
| reada.c | ||
| relocation.c | ||
| root-tree.c | ||
| scrub.c | ||
| send.c | ||
| send.h | ||
| struct-funcs.c | ||
| super.c | ||
| sysfs.c | ||
| sysfs.h | ||
| transaction.c | ||
| transaction.h | ||
| tree-defrag.c | ||
| tree-log.c | ||
| tree-log.h | ||
| ulist.c | ||
| ulist.h | ||
| uuid-tree.c | ||
| volumes.c | ||
| volumes.h | ||
| xattr.c | ||
| xattr.h | ||
| zlib.c | ||