On Tue, Mar 7, 2017 at 10:03 PM, Liu Bo <bo.li.liu@xxxxxxxxxx> wrote:
> On Tue, Mar 07, 2017 at 04:24:49AM +0000, fdmanana@xxxxxxxxxx wrote:
>> From: Filipe Manana <fdmanana@xxxxxxxx>
>>
>> When attempting to COW a file range (we are starting writeback and doing
>> COW), if we manage to reserve an extent for the range we will write into
>> but fail after reserving it and before creating the respective ordered
>> extent, we end up in an error path where we attempt to decrement the
>> data space's bytes_may_use counter after we already did it while
>> reserving the extent, leading to a warning/trace like the following:
>>
>> [ 847.621524] ------------[ cut here ]------------
>> [ 847.625441] WARNING: CPU: 5 PID: 4905 at fs/btrfs/extent-tree.c:4316 btrfs_free_reserved_data_space_noquota+0x60/0x9f [btrfs]
>> [ 847.633704] Modules linked in: btrfs crc32c_generic xor raid6_pq acpi_cpufreq i2c_piix4 ppdev psmouse tpm_tis serio_raw pcspkr parport_pc tpm_tis_core i2c_core sg
>> [ 847.644616] CPU: 5 PID: 4905 Comm: xfs_io Not tainted 4.10.0-rc8-btrfs-next-37+ #2
>> [ 847.648601] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
>> [ 847.648601] Call Trace:
>> [ 847.648601] dump_stack+0x67/0x90
>> [ 847.648601] __warn+0xc2/0xdd
>> [ 847.648601] warn_slowpath_null+0x1d/0x1f
>> [ 847.648601] btrfs_free_reserved_data_space_noquota+0x60/0x9f [btrfs]
>> [ 847.648601] btrfs_clear_bit_hook+0x140/0x258 [btrfs]
>> [ 847.648601] clear_state_bit+0x87/0x128 [btrfs]
>> [ 847.648601] __clear_extent_bit+0x222/0x2b7 [btrfs]
>> [ 847.648601] clear_extent_bit+0x17/0x19 [btrfs]
>> [ 847.648601] extent_clear_unlock_delalloc+0x3b/0x6b [btrfs]
>> [ 847.648601] cow_file_range.isra.39+0x387/0x39a [btrfs]
>> [ 847.648601] run_delalloc_nocow+0x4d7/0x70e [btrfs]
>> [ 847.648601] ? arch_local_irq_save+0x9/0xc
>> [ 847.648601] run_delalloc_range+0xa7/0x2b5 [btrfs]
>> [ 847.648601] writepage_delalloc.isra.31+0xb9/0x15c [btrfs]
>> [ 847.648601] __extent_writepage+0x249/0x2e8 [btrfs]
>> [ 847.648601] extent_write_cache_pages.constprop.33+0x28b/0x36c [btrfs]
>> [ 847.648601] ? arch_local_irq_save+0x9/0xc
>> [ 847.648601] ? mark_lock+0x24/0x201
>> [ 847.648601] extent_writepages+0x4b/0x5c [btrfs]
>> [ 847.648601] ? btrfs_writepage_start_hook+0xed/0xed [btrfs]
>> [ 847.648601] btrfs_writepages+0x28/0x2a [btrfs]
>> [ 847.648601] do_writepages+0x23/0x2c
>> [ 847.648601] __filemap_fdatawrite_range+0x5a/0x61
>> [ 847.648601] filemap_fdatawrite_range+0x13/0x15
>> [ 847.648601] btrfs_fdatawrite_range+0x20/0x46 [btrfs]
>> [ 847.648601] start_ordered_ops+0x19/0x23 [btrfs]
>> [ 847.648601] btrfs_sync_file+0x136/0x42c [btrfs]
>> [ 847.648601] vfs_fsync_range+0x8c/0x9e
>> [ 847.648601] vfs_fsync+0x1c/0x1e
>> [ 847.648601] do_fsync+0x31/0x4a
>> [ 847.648601] SyS_fsync+0x10/0x14
>> [ 847.648601] entry_SYSCALL_64_fastpath+0x18/0xad
>> [ 847.648601] RIP: 0033:0x7f5b05200800
>> [ 847.648601] RSP: 002b:00007ffe204f71c8 EFLAGS: 00000246 ORIG_RAX: 000000000000004a
>> [ 847.648601] RAX: ffffffffffffffda RBX: ffffffff8109637b RCX: 00007f5b05200800
>> [ 847.648601] RDX: 00000000008bd0a0 RSI: 00000000008bd2e0 RDI: 0000000000000003
>> [ 847.648601] RBP: ffffc90001d67f98 R08: 000000000000ffff R09: 000000000000001f
>> [ 847.648601] R10: 00000000000001f6 R11: 0000000000000246 R12: 0000000000000046
>> [ 847.648601] R13: ffffc90001d67f78 R14: 00007f5b054be740 R15: 00007f5b054be740
>> [ 847.648601] ? trace_hardirqs_off_caller+0x3f/0xaa
>> [ 847.685787] ---[ end trace 2a4a3e15382508e8 ]---
>>
>> So fix this by not attempting to decrement the data space info's
>> bytes_may_use counter if we already reserved the extent and an error
>> happened before creating the ordered extent. We are already correctly
>> freeing the reserved extent if an error happens, so there's no additional
>> measure needed.
>>
>> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
>> ---
>>
>> V2: Removed previous dependence on a no longer needed cleanup patch and
>> rebased it on top of Qu's recent patchset that fixes hanging ordered
>> extents when errors happen.
>>
>> fs/btrfs/extent_io.h | 4 +++-
>> fs/btrfs/inode.c | 56 ++++++++++++++++++++++++++++++++++++++--------------
>> 2 files changed, 44 insertions(+), 16 deletions(-)
>>
>> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
>> index 3e4fad4..d31313d 100644
>> --- a/fs/btrfs/extent_io.h
>> +++ b/fs/btrfs/extent_io.h
>> @@ -21,8 +21,10 @@
>> #define EXTENT_NORESERVE (1U << 15)
>> #define EXTENT_QGROUP_RESERVED (1U << 16)
>> #define EXTENT_CLEAR_DATA_RESV (1U << 17)
>> +#define EXTENT_SPACE_FREED (1U << 18)
>> #define EXTENT_IOBITS (EXTENT_LOCKED | EXTENT_WRITEBACK)
>> -#define EXTENT_CTLBITS (EXTENT_DO_ACCOUNTING | EXTENT_FIRST_DELALLOC)
>> +#define EXTENT_CTLBITS (EXTENT_DO_ACCOUNTING | EXTENT_FIRST_DELALLOC |\
>> + EXTENT_SPACE_FREED)
>>
>> /*
>> * flags for bio submission. The high bits indicate the compression
>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>> index 9b03eb9b..9714453 100644
>> --- a/fs/btrfs/inode.c
>> +++ b/fs/btrfs/inode.c
>> @@ -942,10 +942,13 @@ static noinline int cow_file_range(struct inode *inode,
>> u64 num_bytes;
>> unsigned long ram_size;
>> u64 disk_num_bytes;
>> - u64 cur_alloc_size;
>> + u64 cur_alloc_size = 0;
>> u64 blocksize = fs_info->sectorsize;
>> struct btrfs_key ins;
>> struct extent_map *em;
>> + unsigned clear_bits;
>> + unsigned long page_ops;
>> + bool extent_reserved = false;
>> int ret = 0;
>>
>> if (btrfs_is_free_space_inode(BTRFS_I(inode))) {
>> @@ -990,14 +993,14 @@ static noinline int cow_file_range(struct inode *inode,
>> start + num_bytes - 1, 0);
>>
>> while (disk_num_bytes > 0) {
>> - unsigned long op;
>> -
>> cur_alloc_size = disk_num_bytes;
>> ret = btrfs_reserve_extent(root, cur_alloc_size, cur_alloc_size,
>> fs_info->sectorsize, 0, alloc_hint,
>> &ins, 1, 1);
>> if (ret < 0)
>> goto out_unlock;
>> + cur_alloc_size = ins.offset;
>> + extent_reserved = true;
>>
>> ram_size = ins.offset;
>> em = create_io_em(inode, start, ins.offset, /* len */
>> @@ -1012,7 +1015,6 @@ static noinline int cow_file_range(struct inode *inode,
>> goto out_reserve;
>> free_extent_map(em);
>>
>> - cur_alloc_size = ins.offset;
>> ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
>> ram_size, cur_alloc_size, 0);
>> if (ret)
>> @@ -1047,14 +1049,14 @@ static noinline int cow_file_range(struct inode *inode,
>> * Do set the Private2 bit so we know this page was properly
>> * setup for writepage
>> */
>> - op = unlock ? PAGE_UNLOCK : 0;
>> - op |= PAGE_SET_PRIVATE2;
>> + page_ops = unlock ? PAGE_UNLOCK : 0;
>> + page_ops |= PAGE_SET_PRIVATE2;
>>
>> extent_clear_unlock_delalloc(inode, start,
>> start + ram_size - 1,
>> delalloc_end, locked_page,
>> EXTENT_LOCKED | EXTENT_DELALLOC,
>> - op);
>> + page_ops);
>> if (disk_num_bytes > cur_alloc_size)
>> disk_num_bytes = 0;
>> else
>> @@ -1062,6 +1064,7 @@ static noinline int cow_file_range(struct inode *inode,
>> num_bytes -= cur_alloc_size;
>> alloc_hint = ins.objectid + ins.offset;
>> start += cur_alloc_size;
>> + extent_reserved = false;
>>
>> /*
>> * btrfs_reloc_clone_csums() error, since start is increased
>> @@ -1080,12 +1083,35 @@ static noinline int cow_file_range(struct inode *inode,
>> btrfs_dec_block_group_reservations(fs_info, ins.objectid);
>> btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1);
>> out_unlock:
>> + clear_bits = EXTENT_LOCKED | EXTENT_DO_ACCOUNTING | EXTENT_DELALLOC |
>> + EXTENT_DEFRAG;
>> + page_ops = PAGE_UNLOCK | PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK |
>> + PAGE_END_WRITEBACK;
>> + /*
>> + * If we reserved an extent for our delalloc range (or a subrange) and
>> + * failed to create the respective ordered extent, then it means that
>> + * when we reserved the extent we decremented the extent's size from
>> + * the data space_info's bytes_may_use counter and incremented the
>> + * space_info's bytes_reserved counter by the same amount. We must make
>> + * sure extent_clear_unlock_delalloc() does not try to decrement again
>> + * the data space_info's bytes_may_use counter, therefore we pass it the
>> + * flag EXTENT_SPACE_FREED.
>> + */
>
> EXTENT_SPACE_FREED is to free associated metadata only while EXTENT_CLEAR_DATA_RESV is to free data only,
> EXTENT_DO_ACCOUNTING is to free both.
>
> Can we just do
> #define EXTENT_DO_ACCOUNTING (EXTENT_SPACE_FREED | EXTENT_CLEAR_DATA_RESV)
> ?
Exactly like that it wouldn't work. But I understand the idea to
simplify things. Sending a v3 that simplifies things and removes that
new flag.
thanks
>
> Thanks,
>
> -liubo
>> + if (extent_reserved) {
>> + extent_clear_unlock_delalloc(inode, start,
>> + start + cur_alloc_size,
>> + start + cur_alloc_size,
>> + locked_page,
>> + clear_bits | EXTENT_SPACE_FREED,
>> + page_ops);
>> + start += cur_alloc_size;
>> + if (start >= end)
>> + goto out;
>> + }
>> extent_clear_unlock_delalloc(inode, start, end, delalloc_end,
>> locked_page,
>> - EXTENT_LOCKED | EXTENT_DO_ACCOUNTING |
>> - EXTENT_DELALLOC | EXTENT_DEFRAG,
>> - PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
>> - PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK);
>> + clear_bits,
>> + page_ops);
>> goto out;
>> }
>>
>> @@ -1794,10 +1820,10 @@ static void btrfs_clear_bit_hook(struct btrfs_inode *inode,
>> if (btrfs_is_testing(fs_info))
>> return;
>>
>> - if (root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID
>> - && do_list && !(state->state & EXTENT_NORESERVE)
>> - && (*bits & (EXTENT_DO_ACCOUNTING |
>> - EXTENT_CLEAR_DATA_RESV)))
>> + if (root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID &&
>> + do_list && !(state->state & EXTENT_NORESERVE) &&
>> + (*bits & (EXTENT_DO_ACCOUNTING | EXTENT_CLEAR_DATA_RESV)) &&
>> + !(*bits & EXTENT_SPACE_FREED))
>> btrfs_free_reserved_data_space_noquota(
>> &inode->vfs_inode,
>> state->start, len);
>> --
>> 2.7.0.rc3
>>
>> --
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