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| author | Nikolay Borisov <nborisov@suse.com> | 2020-01-30 14:59:44 +0200 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2020-03-23 17:01:43 +0100 |
| commit | 2992df73268f78ec9281692b9b44ae92f3933b54 (patch) | |
| tree | 317bf92dc9d5546f91945f21d23eb0fd2e656bce /fs/btrfs/ctree.h | |
| parent | fd8efa818c55300ffb69c11e573c5ed18cda541c (diff) | |
| download | lwn-2992df73268f78ec9281692b9b44ae92f3933b54.tar.gz lwn-2992df73268f78ec9281692b9b44ae92f3933b54.zip | |
btrfs: Implement DREW lock
A (D)ouble (R)eader (W)riter (E)xclustion lock is a locking primitive
that allows to have multiple readers or multiple writers but not
multiple readers and writers holding it concurrently.
The code is factored out from the existing open-coded locking scheme
used to exclude pending snapshots from nocow writers and vice-versa.
Current implementation actually favors Readers (that is snapshot
creaters) to writers (nocow writers of the filesystem).
The API provides lock/unlock/trylock for reads and writes.
Formal specification for TLA+ provided by Valentin Schneider is at
https://lore.kernel.org/linux-btrfs/2dcaf81c-f0d3-409e-cb29-733d8b3b4cc9@arm.com/
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/ctree.h')
| -rw-r--r-- | fs/btrfs/ctree.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 2ee7d8b4968f..ab8151247b93 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -33,6 +33,7 @@ #include "extent_map.h" #include "async-thread.h" #include "block-rsv.h" +#include "locking.h" struct btrfs_trans_handle; struct btrfs_transaction; |