diff options
| author | Jeff Layton <jlayton@redhat.com> | 2013-06-21 08:58:19 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2013-06-29 12:57:45 +0400 |
| commit | 3999e49364193f7dbbba66e2be655fe91ba1fced (patch) | |
| tree | 5971637ac3b15d5d72797d4050ee35216b9fede1 /Documentation/filesystems | |
| parent | 48f74186546cd5929397856eab209ebcb5692d11 (diff) | |
locks: add a new "lm_owner_key" lock operation
Currently, the hashing that the locking code uses to add these values
to the blocked_hash is simply calculated using fl_owner field. That's
valid in most cases except for server-side lockd, which validates the
owner of a lock based on fl_owner and fl_pid.
In the case where you have a small number of NFS clients doing a lot
of locking between different processes, you could end up with all
the blocked requests sitting in a very small number of hash buckets.
Add a new lm_owner_key operation to the lock_manager_operations that
will generate an unsigned long to use as the key in the hashtable.
That function is only implemented for server-side lockd, and simply
XORs the fl_owner and fl_pid.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/Locking | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index c2963a74fbc3..2db7c9e492e9 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -349,6 +349,7 @@ fl_release_private: maybe no ----------------------- lock_manager_operations --------------------------- prototypes: int (*lm_compare_owner)(struct file_lock *, struct file_lock *); + unsigned long (*lm_owner_key)(struct file_lock *); void (*lm_notify)(struct file_lock *); /* unblock callback */ int (*lm_grant)(struct file_lock *, struct file_lock *, int); void (*lm_break)(struct file_lock *); /* break_lease callback */ @@ -358,16 +359,21 @@ locking rules: inode->i_lock file_lock_lock may block lm_compare_owner: yes[1] maybe no +lm_owner_key yes[1] yes no lm_notify: yes yes no lm_grant: no no no lm_break: yes no no lm_change yes no no -[1]: ->lm_compare_owner is generally called with *an* inode->i_lock held. It -may not be the i_lock of the inode for either file_lock being compared! This is -the case with deadlock detection, since the code has to chase down the owners -of locks that may be entirely unrelated to the one on which the lock is being -acquired. When doing a search for deadlocks, the file_lock_lock is also held. +[1]: ->lm_compare_owner and ->lm_owner_key are generally called with +*an* inode->i_lock held. It may not be the i_lock of the inode +associated with either file_lock argument! This is the case with deadlock +detection, since the code has to chase down the owners of locks that may +be entirely unrelated to the one on which the lock is being acquired. +For deadlock detection however, the file_lock_lock is also held. The +fact that these locks are held ensures that the file_locks do not +disappear out from under you while doing the comparison or generating an +owner key. --------------------------- buffer_head ----------------------------------- prototypes: |