Re: [PATCH 03/20] fs: add FL_LAYOUT lease type

J. Bruce Fields
2015-01-22T20:14:46Z

On Thu, Jan 22, 2015 at 12:09:49PM +0100, Christoph Hellwig wrote:
> This (ab-)uses the file locking code to allow filesystems to recall
> outstanding pNFS layouts on a file. This new lease type is similar but
> not quite the same as FL_DELEG. A FL_LAYOUT lease can always be granted,
> an a per-filesystem lock (XFS iolock for the initial implementation)
> ensures not FL_LAYOUT leases granted when we would need to recall them.

So when there's a conflicting operation it's xfs's responsibility to
call break_layout and wait for the recall?

(And what roughly is the set of conflicting operations?)

--b.

>
> Also included are changes that allow multiple outstanding read
> leases of different types on the same file as long as they have a
> differnt owner. This wasn't a problem until now as nfsd never set
> FL_LEASE leases, and no one else used FL_DELEG leases, but given that
> nfsd will also issues FL_LAYOUT leases we will have to handle it now.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/locks.c | 14 ++++++++++----
> include/linux/fs.h | 16 ++++++++++++++++
> 2 files changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/fs/locks.c b/fs/locks.c
> index 65350a23..6b9772d1 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -137,7 +137,7 @@
>
> #define IS_POSIX(fl) (fl->fl_flags & FL_POSIX)
> #define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK)
> -#define IS_LEASE(fl) (fl->fl_flags & (FL_LEASE|FL_DELEG))
> +#define IS_LEASE(fl) (fl->fl_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
> #define IS_OFDLCK(fl) (fl->fl_flags & FL_OFDLCK)
>
> static bool lease_breaking(struct file_lock *fl)
> @@ -1371,6 +1371,8 @@ static void time_out_leases(struct inode *inode, struct list_head *dispose)
>
> static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker)
> {
> + if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT))
> + return false;
> if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE))
> return false;
> return locks_conflict(breaker, lease);
> @@ -1594,11 +1596,14 @@ int fcntl_getlease(struct file *filp)
> * conflict with the lease we're trying to set.
> */
> static int
> -check_conflicting_open(const struct dentry *dentry, const long arg)
> +check_conflicting_open(const struct dentry *dentry, const long arg, int flags)
> {
> int ret = 0;
> struct inode *inode = dentry->d_inode;
>
> + if (flags & FL_LAYOUT)
> + return 0;
> +
> if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
> return -EAGAIN;
>
> @@ -1647,7 +1652,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
>
> spin_lock(&ctx->flc_lock);
> time_out_leases(inode, &dispose);
> - error = check_conflicting_open(dentry, arg);
> + error = check_conflicting_open(dentry, arg, lease->fl_flags);
> if (error)
> goto out;
>
> @@ -1703,7 +1708,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
> * precedes these checks.
> */
> smp_mb();
> - error = check_conflicting_open(dentry, arg);
> + error = check_conflicting_open(dentry, arg, lease->fl_flags);
> if (error) {
> locks_unlink_lock_ctx(lease, &ctx->flc_lease_cnt);
> goto out;
> @@ -1787,6 +1792,7 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp,
> WARN_ON_ONCE(1);
> return -ENOLCK;
> }
> +
> return generic_add_lease(filp, arg, flp, priv);
> default:
> return -EINVAL;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index f87cb2f..d5658f4 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -875,6 +875,7 @@ static inline struct file *get_file(struct file *f)
> #define FL_DOWNGRADE_PENDING 256 /* Lease is being downgraded */
> #define FL_UNLOCK_PENDING 512 /* Lease is being broken */
> #define FL_OFDLCK 1024 /* lock is "owned" by struct file */
> +#define FL_LAYOUT 2048 /* outstanding pNFS layout */
>
> /*
> * Special return value from posix_lock_file() and vfs_lock_file() for
> @@ -2036,6 +2037,16 @@ static inline int break_deleg_wait(struct inode **delegated_inode)
> return ret;
> }
>
> +static inline int break_layout(struct inode *inode, bool wait)
> +{
> + smp_mb();
> + if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
> + return __break_lease(inode,
> + wait ? O_WRONLY : O_WRONLY | O_NONBLOCK,
> + FL_LAYOUT);
> + return 0;
> +}
> +
> #else /* !CONFIG_FILE_LOCKING */
> static inline int locks_mandatory_locked(struct file *file)
> {
> @@ -2091,6 +2102,11 @@ static inline int break_deleg_wait(struct inode **delegated_inode)
> return 0;
> }
>
> +static inline int break_layout(struct inode *inode, bool wait)
> +{
> + return 0;
> +}
> +
> #endif /* CONFIG_FILE_LOCKING */
>
> /* fs/open.c */
> --
> 1.9.1