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Re: [PATCH 02/18] fs: add FL_LAYOUT lease type

To: Christoph Hellwig <hch@xxxxxx>
Subject: Re: [PATCH 02/18] fs: add FL_LAYOUT lease type
From: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
Date: Tue, 6 Jan 2015 10:46:52 -0800
Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>, linux-nfs@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1420561721-9150-3-git-send-email-hch@xxxxxx>
References: <1420561721-9150-1-git-send-email-hch@xxxxxx> <1420561721-9150-3-git-send-email-hch@xxxxxx>
On Tue,  6 Jan 2015 17:28:25 +0100
Christoph Hellwig <hch@xxxxxx> 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.
> 
> 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@xxxxxx>

So with the current code, layouts are always whole-file?

Tracking layouts as a lease-like object seems reasonable, but I'm not
100% thrilled with overloading all of the lease code with this. Perhaps
it should be its own sort of object with a separate API to manage them?
That would also make it easier to support layouts that are not for the
entire file.

To that end, it might be nice to hold off on taking this until we
deprecate the i_flock list as we can then give layouts their own
list_head in the file_lock_context. It would also make it easier to use
a new sort of object to represent layouts.

I just cleaned up that patchset last week, and will re-post it soon
once I give it a bit of testing this week.

> ---
>  fs/locks.c          | 28 +++++++++++++++++++---------
>  fs/nfsd/nfs4state.c |  2 +-
>  include/linux/fs.h  | 16 ++++++++++++++++
>  3 files changed, 36 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 735b8d3..6cf41f8 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)
> @@ -1348,6 +1348,8 @@ 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);
> @@ -1560,11 +1562,14 @@ 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;
>  
> @@ -1608,7 +1613,7 @@ generic_add_lease(struct file *filp, long arg, struct 
> file_lock **flp, void **pr
>  
>       spin_lock(&inode->i_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;
>  
> @@ -1624,10 +1629,13 @@ generic_add_lease(struct file *filp, long arg, struct 
> file_lock **flp, void **pr
>       for (before = &inode->i_flock;
>                       ((fl = *before) != NULL) && IS_LEASE(fl);
>                       before = &fl->fl_next) {
> -             if (fl->fl_file == filp) {
> +
> +             if (fl->fl_file == filp &&
> +                 fl->fl_owner == lease->fl_owner) {
>                       my_before = before;
>                       continue;
>               }
> +
>               /*
>                * No exclusive leases if someone else has a lease on
>                * this file:
> @@ -1665,7 +1673,7 @@ 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)
>               goto out_unlink;
>  
> @@ -1685,7 +1693,7 @@ out_unlink:
>       goto out;
>  }
>  
> -static int generic_delete_lease(struct file *filp)
> +static int generic_delete_lease(struct file *filp, void *priv)
>  {
>       int error = -EAGAIN;
>       struct file_lock *fl, **before;
> @@ -1698,7 +1706,8 @@ static int generic_delete_lease(struct file *filp)
>       for (before = &inode->i_flock;
>                       ((fl = *before) != NULL) && IS_LEASE(fl);
>                       before = &fl->fl_next) {
> -             if (fl->fl_file == filp)
> +             if (fl->fl_file == filp &&
> +                 priv == fl->fl_owner)
>                       break;
>       }
>       trace_generic_delete_lease(inode, fl);
> @@ -1737,13 +1746,14 @@ int generic_setlease(struct file *filp, long arg, 
> struct file_lock **flp,
>  
>       switch (arg) {
>       case F_UNLCK:
> -             return generic_delete_lease(filp);
> +             return generic_delete_lease(filp, *priv);
>       case F_RDLCK:
>       case F_WRLCK:
>               if (!(*flp)->fl_lmops->lm_break) {
>                       WARN_ON_ONCE(1);
>                       return -ENOLCK;
>               }
> +
>               return generic_add_lease(filp, arg, flp, priv);
>       default:
>               return -EINVAL;
> @@ -1816,7 +1826,7 @@ static int do_fcntl_add_lease(unsigned int fd, struct 
> file *filp, long arg)
>  int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
>  {
>       if (arg == F_UNLCK)
> -             return vfs_setlease(filp, F_UNLCK, NULL, NULL);
> +             return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
>       return do_fcntl_add_lease(fd, filp, arg);
>  }
>  
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 277f8b8..2505b68 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -693,7 +693,7 @@ static void nfs4_put_deleg_lease(struct nfs4_file *fp)
>       spin_unlock(&fp->fi_lock);
>  
>       if (filp) {
> -             vfs_setlease(filp, F_UNLCK, NULL, NULL);
> +             vfs_setlease(filp, F_UNLCK, NULL, (void **)&fp);
>               fput(filp);
>       }
>  }
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index f90c028..204cf91 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
> @@ -2017,6 +2018,16 @@ 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_flock)
> +             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)
>  {
> @@ -2072,6 +2083,11 @@ 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 */


-- 
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>

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