On Tue, Mar 07, 2017 at 08:41:06PM +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.
>
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Thanks,
-liubo
> 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.
>
> V3: Simplified extent flags used for freeing reserved metadata and data.
>
> fs/btrfs/extent_io.h | 4 +++-
> fs/btrfs/inode.c | 59 +++++++++++++++++++++++++++++++++++++---------------
> 2 files changed, 45 insertions(+), 18 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index 3e4fad4..48a30d0 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -14,7 +14,7 @@
> #define EXTENT_DEFRAG (1U << 6)
> #define EXTENT_BOUNDARY (1U << 9)
> #define EXTENT_NODATASUM (1U << 10)
> -#define EXTENT_DO_ACCOUNTING (1U << 11)
> +#define EXTENT_CLEAR_META_RESV (1U << 11)
> #define EXTENT_FIRST_DELALLOC (1U << 12)
> #define EXTENT_NEED_WAIT (1U << 13)
> #define EXTENT_DAMAGED (1U << 14)
> @@ -22,6 +22,8 @@
> #define EXTENT_QGROUP_RESERVED (1U << 16)
> #define EXTENT_CLEAR_DATA_RESV (1U << 17)
> #define EXTENT_IOBITS (EXTENT_LOCKED | EXTENT_WRITEBACK)
> +#define EXTENT_DO_ACCOUNTING (EXTENT_CLEAR_META_RESV | \
> + EXTENT_CLEAR_DATA_RESV)
> #define EXTENT_CTLBITS (EXTENT_DO_ACCOUNTING | EXTENT_FIRST_DELALLOC)
>
> /*
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 9b03eb9b..c8ce47a 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_DELALLOC | EXTENT_DEFRAG |
> + EXTENT_CLEAR_META_RESV;
> + 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 do not pass
> + * it the flag EXTENT_CLEAR_DATA_RESV.
> + */
> + if (extent_reserved) {
> + extent_clear_unlock_delalloc(inode, start,
> + start + cur_alloc_size,
> + start + cur_alloc_size,
> + locked_page,
> + clear_bits,
> + 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 | EXTENT_CLEAR_DATA_RESV,
> + page_ops);
> goto out;
> }
>
> @@ -1775,7 +1801,7 @@ static void btrfs_clear_bit_hook(struct btrfs_inode *inode,
>
> if (*bits & EXTENT_FIRST_DELALLOC) {
> *bits &= ~EXTENT_FIRST_DELALLOC;
> - } else if (!(*bits & EXTENT_DO_ACCOUNTING)) {
> + } else if (!(*bits & EXTENT_CLEAR_META_RESV)) {
> spin_lock(&inode->lock);
> inode->outstanding_extents -= num_extents;
> spin_unlock(&inode->lock);
> @@ -1786,7 +1812,7 @@ static void btrfs_clear_bit_hook(struct btrfs_inode *inode,
> * don't need to call dellalloc_release_metadata if there is an
> * error.
> */
> - if (*bits & EXTENT_DO_ACCOUNTING &&
> + if (*bits & EXTENT_CLEAR_META_RESV &&
> root != fs_info->tree_root)
> btrfs_delalloc_release_metadata(inode, len);
>
> @@ -1794,10 +1820,9 @@ 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_CLEAR_DATA_RESV))
> btrfs_free_reserved_data_space_noquota(
> &inode->vfs_inode,
> state->start, len);
> --
> 2.7.0.rc3
>
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