On Thu, Jan 21, 2021 at 02:13:54PM +0800, Qu Wenruo wrote:
> [BUG]
> There is a long existing bug in the last parameter of
> btrfs_add_ordered_extent(), in commit 771ed689d2cd ("Btrfs: Optimize
> compressed writeback and reads") back to 2008.
>
> In that ancient commit btrfs_add_ordered_extent() expects the @type
> parameter to be one of the following:
> - BTRFS_ORDERED_REGULAR
> - BTRFS_ORDERED_NOCOW
> - BTRFS_ORDERED_PREALLOC
> - BTRFS_ORDERED_COMPRESSED
>
> But we pass 0 in cow_file_range(), which means BTRFS_ORDERED_IO_DONE.
>
> Ironically extra check in __btrfs_add_ordered_extent() won't set the bit
> if we're seeing (type == IO_DONE || type == IO_COMPLETE), and avoid any
> obvious bug.
>
> But this still leads to regular COW ordered extent having no bit to
> indicate its type in various trace events, rendering REGULAR bit
> useless.
>
> [FIX]
> This patch will change the following aspects to avoid such problem:
> - Reorder btrfs_ordered_extent::flags
> Now the type bits go first (REGULAR/NOCOW/PREALLCO/COMPRESSED), then
> DIRECT bit, finally extra status bits like IO_DONE/COMPLETE/IOERR.
>
> - Add extra ASSERT() for btrfs_add_ordered_extent_*()
>
> - Remove @type parameter for btrfs_add_ordered_extent_compress()
> As the only valid @type here is BTRFS_ORDERED_COMPRESSED.
>
> - Remove the unnecessary special check for IO_DONE/COMPLETE in
> __btrfs_add_ordered_extent()
> This is just to make the code work, with extra ASSERT(), there are
> limited values can be passed in.
>
> Signed-off-by: Qu Wenruo <[email protected]>
Added to misc-next thanks.
> ---
> fs/btrfs/inode.c | 4 ++--
> fs/btrfs/ordered-data.c | 18 +++++++++++++-----
> fs/btrfs/ordered-data.h | 37 +++++++++++++++++++++++-------------
> include/trace/events/btrfs.h | 7 ++++---
> 4 files changed, 43 insertions(+), 23 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index ef6cb7b620d0..ea9056cc5559 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -917,7 +917,6 @@ static noinline void submit_compressed_extents(struct
> async_chunk *async_chunk)
> ins.objectid,
> async_extent->ram_size,
> ins.offset,
> - BTRFS_ORDERED_COMPRESSED,
> async_extent->compress_type);
> if (ret) {
> btrfs_drop_extent_cache(inode, async_extent->start,
> @@ -1127,7 +1126,8 @@ static noinline int cow_file_range(struct btrfs_inode
> *inode,
> free_extent_map(em);
>
> ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
> - ram_size, cur_alloc_size, 0);
> + ram_size, cur_alloc_size,
> + BTRFS_ORDERED_REGULAR);
> if (ret)
> goto out_drop_extent_cache;
>
> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
> index d5d326c674b1..bd7e187d9b16 100644
> --- a/fs/btrfs/ordered-data.c
> +++ b/fs/btrfs/ordered-data.c
> @@ -199,8 +199,11 @@ static int __btrfs_add_ordered_extent(struct btrfs_inode
> *inode, u64 file_offset
> entry->compress_type = compress_type;
> entry->truncated_len = (u64)-1;
> entry->qgroup_rsv = ret;
> - if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
> - set_bit(type, &entry->flags);
> +
> + ASSERT(type == BTRFS_ORDERED_REGULAR || type == BTRFS_ORDERED_NOCOW ||
> + type == BTRFS_ORDERED_PREALLOC ||
> + type == BTRFS_ORDERED_COMPRESSED);
I've reformatted that so that all the checks are on separate lines, it's
easier to read though it does not fill the whole line.
> + set_bit(type, &entry->flags);
>
> if (dio) {
> percpu_counter_add_batch(&fs_info->dio_bytes, num_bytes,
> @@ -256,6 +259,8 @@ int btrfs_add_ordered_extent(struct btrfs_inode *inode,
> u64 file_offset,
> u64 disk_bytenr, u64 num_bytes, u64 disk_num_bytes,
> int type)
> {
> + ASSERT(type == BTRFS_ORDERED_REGULAR || type == BTRFS_ORDERED_NOCOW ||
> + type == BTRFS_ORDERED_PREALLOC);
> return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
> num_bytes, disk_num_bytes, type, 0,
> BTRFS_COMPRESS_NONE);
> @@ -265,6 +270,8 @@ int btrfs_add_ordered_extent_dio(struct btrfs_inode
> *inode, u64 file_offset,
> u64 disk_bytenr, u64 num_bytes,
> u64 disk_num_bytes, int type)
> {
> + ASSERT(type == BTRFS_ORDERED_REGULAR || type == BTRFS_ORDERED_NOCOW ||
> + type == BTRFS_ORDERED_PREALLOC);
> return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
> num_bytes, disk_num_bytes, type, 1,
> BTRFS_COMPRESS_NONE);
> @@ -272,11 +279,12 @@ int btrfs_add_ordered_extent_dio(struct btrfs_inode
> *inode, u64 file_offset,
>
> int btrfs_add_ordered_extent_compress(struct btrfs_inode *inode, u64
> file_offset,
> u64 disk_bytenr, u64 num_bytes,
> - u64 disk_num_bytes, int type,
> - int compress_type)
> + u64 disk_num_bytes, int compress_type)
> {
> + ASSERT(compress_type != BTRFS_COMPRESS_NONE);
> return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
> - num_bytes, disk_num_bytes, type, 0,
> + num_bytes, disk_num_bytes,
> + BTRFS_ORDERED_COMPRESSED, 0,
> compress_type);
> }
>
> diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
> index 46194c2c05d4..151ec6bba405 100644
> --- a/fs/btrfs/ordered-data.h
> +++ b/fs/btrfs/ordered-data.h
> @@ -27,7 +27,7 @@ struct btrfs_ordered_sum {
> };
>
> /*
> - * bits for the flags field:
> + * Bits for btrfs_ordered_extent::flags.
> *
> * BTRFS_ORDERED_IO_DONE is set when all of the blocks are written.
> * It is used to make sure metadata is inserted into the tree only once
> @@ -38,24 +38,36 @@ struct btrfs_ordered_sum {
> * IO is done and any metadata is inserted into the tree.
> */
> enum {
> + /*
> + * Different types for direct io, one and only one of the 4 type can
direct io
> + * be set when creating ordered extent.
> + *
> + * REGULAR: For regular non-compressed COW write
> + * NOCOW: For NOCOW write into existing non-hole extent
> + * PREALLOC: For NOCOW write into preallocated extent
> + * COMPRESSED: For compressed COW write
> + */
> + BTRFS_ORDERED_REGULAR,
> + BTRFS_ORDERED_NOCOW,
> + BTRFS_ORDERED_PREALLOC,
> + BTRFS_ORDERED_COMPRESSED,
> +
> + /*
> + * Extra bit for DirectIO, can only be set for
DirectIO
> + * REGULAR/NOCOW/PREALLOC. No DIO for compressed extent.
DIO
Three different ways to spell that but one is enough. Fixed.
