Btrfs: fix enospc error caused by wrong checks of the chunk (9e622d6b) · Commits · 戴 / test

When we did sysbench test for inline files, enospc error happened easily though there was lots of free disk space which could be allocated for new chunks. Reproduce steps: # mkfs.btrfs -b $((2 * 1024 * 1024 * 1024)) <test partition> # mount <test partition> /mnt # ulimit -n 102400 # cd /mnt # sysbench --num-threads=1 --test=fileio --file-num=81920 \ > --file-total-size=80M --file-block-size=1K --file-io-mode=sync \ > --file-test-mode=seqwr prepare # sysbench --num-threads=1 --test=fileio --file-num=81920 \ > --file-total-size=80M --file-block-size=1K --file-io-mode=sync \ > --file-test-mode=seqwr run <soon later, BUG_ON() was triggered by enospc error> The reason of this bug is: Now, we can reserve space which is larger than the free space in the chunks if we have enough free disk space which can be used for new chunks. By this way, the space allocator should allocate a new chunk by force if there is no free space in the free space cache. But there are two wrong checks which break this operation. One is if (ret == -ENOSPC && num_bytes > min_alloc_size) in btrfs_reserve_extent(), it is wrong, we should try to allocate a new chunk even we fail to allocate free space by minimum allocable size. The other is if (space_info->force_alloc) force = space_info->force_alloc; in do_chunk_alloc(). It makes the allocator ignore CHUNK_ALLOC_FORCE If someone sets ->force_alloc to CHUNK_ALLOC_LIMITED, and makes the enospc error happen. Fix these two wrong checks. Especially the second one, we fix it by changing the value of CHUNK_ALLOC_LIMITED and CHUNK_ALLOC_FORCE, and make CHUNK_ALLOC_FORCE greater than CHUNK_ALLOC_LIMITED since CHUNK_ALLOC_FORCE has higher priority. And if the value which is passed in by the caller is greater than ->force_alloc, use the passed value. Signed-off-by:

Miao Xie <miaox@cn.fujitsu.com> Signed-off-by:

Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent-tree.c

+27 −22

Original line number	Diff line number	Diff line
		@@ -34,23 +34,24 @@
		#include "locking.h"
		#include "free-space-cache.h"

		/* control flags for do_chunk_alloc's force field
		/*
		* control flags for do_chunk_alloc's force field
		* CHUNK_ALLOC_NO_FORCE means to only allocate a chunk
		* if we really need one.
		*
		* CHUNK_ALLOC_FORCE means it must try to allocate one
		*
		* CHUNK_ALLOC_LIMITED means to only try and allocate one
		* if we have very few chunks already allocated. This is
		* used as part of the clustering code to help make sure
		* we have a good pool of storage to cluster in, without
		* filling the FS with empty chunks
		*
		* CHUNK_ALLOC_FORCE means it must try to allocate one
		*
		*/
		enum {
		CHUNK_ALLOC_NO_FORCE = 0,
		CHUNK_ALLOC_FORCE = 1,
		CHUNK_ALLOC_LIMITED = 2,
		CHUNK_ALLOC_LIMITED = 1,
		CHUNK_ALLOC_FORCE = 2,
		};

		/*
		@@ -3414,7 +3415,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,

		again:
		spin_lock(&space_info->lock);
		if (space_info->force_alloc)
		if (force < space_info->force_alloc)
		force = space_info->force_alloc;
		if (space_info->full) {
		spin_unlock(&space_info->lock);
		@@ -5794,6 +5795,7 @@ int btrfs_reserve_extent(struct btrfs_trans_handle *trans,
		u64 search_end, struct btrfs_key *ins,
		u64 data)
		{
		bool final_tried = false;
		int ret;
		u64 search_start = 0;

		@@ -5813,15 +5815,17 @@ again:
		search_start, search_end, hint_byte,
		ins, data);

		if (ret == -ENOSPC && num_bytes > min_alloc_size) {
		if (ret == -ENOSPC) {
		if (!final_tried) {
		num_bytes = num_bytes >> 1;
		num_bytes = num_bytes & ~(root->sectorsize - 1);
		num_bytes = max(num_bytes, min_alloc_size);
		do_chunk_alloc(trans, root->fs_info->extent_root,
		num_bytes, data, CHUNK_ALLOC_FORCE);
		if (num_bytes == min_alloc_size)
		final_tried = true;
		goto again;
		}
		if (ret == -ENOSPC && btrfs_test_opt(root, ENOSPC_DEBUG)) {
		} else if (btrfs_test_opt(root, ENOSPC_DEBUG)) {
		struct btrfs_space_info *sinfo;

		sinfo = __find_space_info(root->fs_info, data);
		@@ -5830,6 +5834,7 @@ again:
		(unsigned long long)num_bytes);
		dump_space_info(sinfo, num_bytes, 1);
		}
		}

		trace_btrfs_reserved_extent_alloc(root, ins->objectid, ins->offset);

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