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btrfs: introduce try-lock semantics for exclusive op start

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Add try-lock for exclusive operation start to allow callers to do more
checks. The same operation must already be running. The try-lock and
unlock must pair and are a substitute for btrfs_exclop_start, thus it
must also pair with btrfs_exclop_finish to release the exclop context.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2021-05-18 21:05:52 +02:00
parent 907d2710d7
commit 578bda9e17
2 changed files with 29 additions and 0 deletions
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3
fs/btrfs/ctree.h
View File

@ -3233,6 +3233,9 @@ void btrfs_update_ioctl_balance_args(struct btrfs_fs_info *fs_info,
struct btrfs_ioctl_balance_args *bargs);
bool btrfs_exclop_start(struct btrfs_fs_info *fs_info,
enum btrfs_exclusive_operation type);
bool btrfs_exclop_start_try_lock(struct btrfs_fs_info *fs_info,
enum btrfs_exclusive_operation type);
void btrfs_exclop_start_unlock(struct btrfs_fs_info *fs_info);
void btrfs_exclop_finish(struct btrfs_fs_info *fs_info);
/* file.c */

26
fs/btrfs/ioctl.c
View File

@ -371,6 +371,32 @@ bool btrfs_exclop_start(struct btrfs_fs_info *fs_info,
return ret;
}
/*
* Conditionally allow to enter the exclusive operation in case it's compatible
* with the running one. This must be paired with btrfs_exclop_start_unlock and
* btrfs_exclop_finish.
*
* Compatibility:
* - the same type is already running
* - not BTRFS_EXCLOP_NONE - this is intentionally incompatible and the caller
* must check the condition first that would allow none -> @type
*/
bool btrfs_exclop_start_try_lock(struct btrfs_fs_info *fs_info,
enum btrfs_exclusive_operation type)
{
spin_lock(&fs_info->super_lock);
if (fs_info->exclusive_operation == type)
return true;
spin_unlock(&fs_info->super_lock);
return false;
}
void btrfs_exclop_start_unlock(struct btrfs_fs_info *fs_info)
{
spin_unlock(&fs_info->super_lock);
}
void btrfs_exclop_finish(struct btrfs_fs_info *fs_info)
{
spin_lock(&fs_info->super_lock);