From: Anand Jain <anand.jain@oracle.com>
To: David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH] btrfs: track exclusive filesystem operation in flags
Date: Wed, 29 Mar 2017 18:01:37 +0800 [thread overview]
Message-ID: <ac95c9c4-ed2b-3a9f-f763-697bd63db56f@oracle.com> (raw)
In-Reply-To: <20170328124421.30585-1-dsterba@suse.com>
On 03/28/2017 08:44 PM, David Sterba wrote:
> There are several operations, usually started from ioctls, that cannot
> run concurrently. The status is tracked in
> mutually_exclusive_operation_running as an atomic_t. We can easily track
> the status as one of the per-filesystem flag bits with same
> synchronization guarantees.
>
> The conversion replaces:
>
> * atomic_xchg(..., 1) -> test_and_set_bit(FLAG, ...)
> * atomic_set(..., 0) -> clear_bit(FLAG, ...)
Makes sense.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
However in the long term do you think its better to have
BTRFS_FS_EXCL_OP flag in the struct btrfs_fs_devices
rather than in struct btrfs_fs_info ? because we don't have
fs_info until device is mounted and in the long term we could
have a feature where volume can be maintained just after the
device scan without device being mounted.
Thanks, Anand
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
> fs/btrfs/ctree.h | 7 +++++--
> fs/btrfs/dev-replace.c | 5 ++---
> fs/btrfs/ioctl.c | 33 +++++++++++++++------------------
> fs/btrfs/volumes.c | 6 +++---
> 4 files changed, 25 insertions(+), 26 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 29b7fc28c607..2521752c4e4a 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -702,6 +702,11 @@ struct btrfs_delayed_root;
> #define BTRFS_FS_BTREE_ERR 11
> #define BTRFS_FS_LOG1_ERR 12
> #define BTRFS_FS_LOG2_ERR 13
> +/*
> + * Indicate that a whole-filesystem exclusive operation is running
> + * (device replace, resize, device add/delete, balance)
> + */
> +#define BTRFS_FS_EXCL_OP 14
>
> struct btrfs_fs_info {
> u8 fsid[BTRFS_FSID_SIZE];
> @@ -1067,8 +1072,6 @@ struct btrfs_fs_info {
> /* device replace state */
> struct btrfs_dev_replace dev_replace;
>
> - atomic_t mutually_exclusive_operation_running;
> -
> struct percpu_counter bio_counter;
> wait_queue_head_t replace_wait;
>
> diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
> index e653921f05d9..de7b2c897fe0 100644
> --- a/fs/btrfs/dev-replace.c
> +++ b/fs/btrfs/dev-replace.c
> @@ -784,8 +784,7 @@ int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
> }
> btrfs_dev_replace_unlock(dev_replace, 1);
>
> - WARN_ON(atomic_xchg(
> - &fs_info->mutually_exclusive_operation_running, 1));
> + WARN_ON(test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
> task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
> return PTR_ERR_OR_ZERO(task);
> }
> @@ -814,7 +813,7 @@ static int btrfs_dev_replace_kthread(void *data)
> (unsigned int)progress);
> }
> btrfs_dev_replace_continue_on_mount(fs_info);
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
>
> return 0;
> }
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index dabfc7ac48a6..a29dc3fd7152 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1504,7 +1504,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
> if (ret)
> return ret;
>
> - if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
> + if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
> mnt_drop_write_file(file);
> return BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
> }
> @@ -1619,7 +1619,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
> kfree(vol_args);
> out:
> mutex_unlock(&fs_info->volume_mutex);
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> mnt_drop_write_file(file);
> return ret;
> }
> @@ -2661,7 +2661,7 @@ static long btrfs_ioctl_add_dev(struct btrfs_fs_info *fs_info, void __user *arg)
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1))
> + if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags))
> return BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
>
> mutex_lock(&fs_info->volume_mutex);
> @@ -2680,7 +2680,7 @@ static long btrfs_ioctl_add_dev(struct btrfs_fs_info *fs_info, void __user *arg)
> kfree(vol_args);
> out:
> mutex_unlock(&fs_info->volume_mutex);
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> return ret;
> }
>
> @@ -2708,7 +2708,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
> if (vol_args->flags & ~BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED)
> return -EOPNOTSUPP;
>
> - if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
> + if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
> ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
> goto out;
> }
> @@ -2721,7 +2721,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
> ret = btrfs_rm_device(fs_info, vol_args->name, 0);
> }
> mutex_unlock(&fs_info->volume_mutex);
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
>
> if (!ret) {
> if (vol_args->flags & BTRFS_DEVICE_SPEC_BY_ID)
> @@ -2752,7 +2752,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
> if (ret)
> return ret;
>
> - if (atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
> + if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
> ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
> goto out_drop_write;
> }
> @@ -2772,7 +2772,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
> btrfs_info(fs_info, "disk deleted %s", vol_args->name);
> kfree(vol_args);
> out:
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> out_drop_write:
> mnt_drop_write_file(file);
>
> @@ -4442,13 +4442,11 @@ static long btrfs_ioctl_dev_replace(struct btrfs_fs_info *fs_info,
> ret = -EROFS;
> goto out;
> }
> - if (atomic_xchg(
> - &fs_info->mutually_exclusive_operation_running, 1)) {
> + if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
> ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
> } else {
> ret = btrfs_dev_replace_by_ioctl(fs_info, p);
> - atomic_set(
> - &fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> }
> break;
> case BTRFS_IOCTL_DEV_REPLACE_CMD_STATUS:
> @@ -4643,7 +4641,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
> return ret;
>
> again:
> - if (!atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
> + if (!test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
> mutex_lock(&fs_info->volume_mutex);
> mutex_lock(&fs_info->balance_mutex);
> need_unlock = true;
> @@ -4689,7 +4687,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
> }
>
> locked:
> - BUG_ON(!atomic_read(&fs_info->mutually_exclusive_operation_running));
> + BUG_ON(!test_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
>
> if (arg) {
> bargs = memdup_user(arg, sizeof(*bargs));
> @@ -4745,11 +4743,10 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
>
> do_balance:
> /*
> - * Ownership of bctl and mutually_exclusive_operation_running
> + * Ownership of bctl and filesystem flag BTRFS_FS_EXCL_OP
> * goes to to btrfs_balance. bctl is freed in __cancel_balance,
> * or, if restriper was paused all the way until unmount, in
> - * free_fs_info. mutually_exclusive_operation_running is
> - * cleared in __cancel_balance.
> + * free_fs_info. The flag is cleared in __cancel_balance.
> */
> need_unlock = false;
>
> @@ -4769,7 +4766,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
> mutex_unlock(&fs_info->balance_mutex);
> mutex_unlock(&fs_info->volume_mutex);
> if (need_unlock)
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> out:
> mnt_drop_write_file(file);
> return ret;
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 73d56eef5e60..91580cf471e4 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -3736,7 +3736,7 @@ static void __cancel_balance(struct btrfs_fs_info *fs_info)
> if (ret)
> btrfs_handle_fs_error(fs_info, ret, NULL);
>
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> }
>
> /* Non-zero return value signifies invalidity */
> @@ -3910,7 +3910,7 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
> __cancel_balance(fs_info);
> else {
> kfree(bctl);
> - atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
> + clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> }
> return ret;
> }
> @@ -4000,7 +4000,7 @@ int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
> btrfs_balance_sys(leaf, item, &disk_bargs);
> btrfs_disk_balance_args_to_cpu(&bctl->sys, &disk_bargs);
>
> - WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));
> + WARN_ON(test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
>
> mutex_lock(&fs_info->volume_mutex);
> mutex_lock(&fs_info->balance_mutex);
>
next prev parent reply other threads:[~2017-03-29 9:56 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-28 12:44 [PATCH] btrfs: track exclusive filesystem operation in flags David Sterba
2017-03-29 10:01 ` Anand Jain [this message]
2017-03-29 13:21 ` David Sterba
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