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| author | Naohiro Aota <naohiro.aota@wdc.com> | 2024-02-02 13:23:28 +0900 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2024-03-04 16:24:47 +0100 |
| commit | 4dc4a3be6cc4ef0a04785124afb0bd4fd06298ff (patch) | |
| tree | 025f6217aab3402a67451979fb1d9466d0a873d8 | |
| parent | e383e158ed1b6abc2d2d3e6736d77a46393f80fa (diff) | |
| download | linux-4dc4a3be6cc4ef0a04785124afb0bd4fd06298ff.tar.gz linux-4dc4a3be6cc4ef0a04785124afb0bd4fd06298ff.tar.bz2 linux-4dc4a3be6cc4ef0a04785124afb0bd4fd06298ff.zip | |
btrfs: use READ/WRITE_ONCE for fs_devices->read_policy
Since we can read/modify the value from the sysfs interface concurrently,
it would be better to protect it from compiler optimizations.
Currently, there is only one read policy BTRFS_READ_POLICY_PID available,
so no actual problem can happen now. This is a preparation for the future
expansion.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/sysfs.c | 7 | ||||
| -rw-r--r-- | fs/btrfs/volumes.c | 10 |
2 files changed, 9 insertions, 8 deletions
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 84c05246ffd8..21586ecc35bf 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -1228,11 +1228,12 @@ static ssize_t btrfs_read_policy_show(struct kobject *kobj, struct kobj_attribute *a, char *buf) { struct btrfs_fs_devices *fs_devices = to_fs_devs(kobj); + const enum btrfs_read_policy policy = READ_ONCE(fs_devices->read_policy); ssize_t ret = 0; int i; for (i = 0; i < BTRFS_NR_READ_POLICY; i++) { - if (fs_devices->read_policy == i) + if (policy == i) ret += sysfs_emit_at(buf, ret, "%s[%s]", (ret == 0 ? "" : " "), btrfs_read_policy_name[i]); @@ -1256,8 +1257,8 @@ static ssize_t btrfs_read_policy_store(struct kobject *kobj, for (i = 0; i < BTRFS_NR_READ_POLICY; i++) { if (sysfs_streq(buf, btrfs_read_policy_name[i])) { - if (i != fs_devices->read_policy) { - fs_devices->read_policy = i; + if (i != READ_ONCE(fs_devices->read_policy)) { + WRITE_ONCE(fs_devices->read_policy, i); btrfs_info(fs_devices->fs_info, "read policy set to '%s'", btrfs_read_policy_name[i]); diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 474ab7ed65ea..224345658ea5 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5942,6 +5942,7 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info, struct btrfs_chunk_map *map, int first, int dev_replace_is_ongoing) { + const enum btrfs_read_policy policy = READ_ONCE(fs_info->fs_devices->read_policy); int i; int num_stripes; int preferred_mirror; @@ -5956,13 +5957,12 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info, else num_stripes = map->num_stripes; - switch (fs_info->fs_devices->read_policy) { + switch (policy) { default: /* Shouldn't happen, just warn and use pid instead of failing */ - btrfs_warn_rl(fs_info, - "unknown read_policy type %u, reset to pid", - fs_info->fs_devices->read_policy); - fs_info->fs_devices->read_policy = BTRFS_READ_POLICY_PID; + btrfs_warn_rl(fs_info, "unknown read_policy type %u, reset to pid", + policy); + WRITE_ONCE(fs_info->fs_devices->read_policy, BTRFS_READ_POLICY_PID); fallthrough; case BTRFS_READ_POLICY_PID: preferred_mirror = first + (current->pid % num_stripes); |