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btrfs: zoned: fix deadlock waiting for ticket during data relocation

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When performing data relocation on a zoned filesystem, BTRFS can deadlock
in handle_reserve_tickets(). The relocation process is waiting on a space
reservation ticket that can never be fulfilled, because the relocation
itself is the operation responsible for freeing up that space.

Fix this by introducing a new flush state,
BTRFS_RESERVE_FLUSH_ZONED_RELOCATION, specifically for data chunk
allocation during zoned relocation. Like
BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE, this state uses
priority_reclaim_data_space() instead of the normal flushing path, which
avoids re-entering the relocation code and breaking the deadlock cycle.

In btrfs_alloc_data_chunk_ondemand(), select this new flush state when the
inode belongs to a data relocation root on a zoned filesystem.

Fixes: e2a7fd2237 ("btrfs: zoned: add zone reclaim flush state for DATA space_info")
Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Johannes Thumshirn
2026-05-22 11:02:47 +02:00
parent 52416a27aa
commit 814c3b4ea3
3 changed files with 15 additions and 0 deletions
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2
fs/btrfs/delalloc-space.c
View File

@@ -134,6 +134,8 @@ int btrfs_alloc_data_chunk_ondemand(const struct btrfs_inode *inode, u64 bytes)
if (btrfs_is_free_space_inode(inode))
flush = BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE;
else if (btrfs_is_zoned(fs_info) && btrfs_is_data_reloc_root(root))
flush = BTRFS_RESERVE_FLUSH_ZONED_RELOCATION;
return btrfs_reserve_data_bytes(data_sinfo_for_inode(inode), bytes, flush);
}

2
fs/btrfs/space-info.c
View File

@@ -1705,6 +1705,7 @@ static int handle_reserve_ticket(struct btrfs_space_info *space_info,
ARRAY_SIZE(evict_flush_states));
break;
case BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE:
case BTRFS_RESERVE_FLUSH_ZONED_RELOCATION:
priority_reclaim_data_space(space_info, ticket);
break;
default:
@@ -1968,6 +1969,7 @@ int btrfs_reserve_data_bytes(struct btrfs_space_info *space_info, u64 bytes,
ASSERT(flush == BTRFS_RESERVE_FLUSH_DATA ||
flush == BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE ||
flush == BTRFS_RESERVE_FLUSH_ZONED_RELOCATION ||
flush == BTRFS_RESERVE_NO_FLUSH, "flush=%d", flush);
ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA,
"current->journal_info=0x%lx flush=%d",

11
fs/btrfs/space-info.h
View File

@@ -77,6 +77,17 @@ enum btrfs_reserve_flush_enum {
*/
BTRFS_RESERVE_FLUSH_ALL_STEAL,
/*
* This is for relocation on zoned filesystems only. We need to use
* priority flushing for this, because otherwise we can deadlock on
* waiting for a ticket, that cannot be granted, because we cannot do
* any allocations.
*
* Apart from being specific to zoned relocation, it is equal to
* BTRFS_FLUSH_FREE_SPACE_INODE.
*/
BTRFS_RESERVE_FLUSH_ZONED_RELOCATION,
/*
* This is for btrfs_use_block_rsv only. We have exhausted our block
* rsv and our global block rsv. This can happen for things like