From: NeilBrown <neilb@suse.com>
To: Jeff Layton <jlayton@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
Martin Wilck <mwilck@suse.de>,
linux-fsdevel@vger.kernel.org,
Frank Filz <ffilzlnx@mindspring.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 3/5] fs/locks: change all *_conflict() functions to return a new enum.
Date: Thu, 09 Aug 2018 12:04:41 +1000 [thread overview]
Message-ID: <153378028114.1220.3708291796442871726.stgit@noble> (raw)
In-Reply-To: <153378012255.1220.6754153662007899557.stgit@noble>
In a future patch we will need to differentiate between conflicts that
are "transitive" and those that aren't.
A "transitive" conflict is defined as one where any lock that
conflicts with the first (newly requested) lock would conflict with
the existing lock.
So change posix_locks_conflict(), flock_locks_conflict() (both
currently returning int) and leases_conflict() (currently returning
bool) to return "enum conflict".
Add locks_transitive_overlap() to make it possible to compute the
correct conflict for posix locks.
The FL_NO_CONFLICT value is zero, so current code which only tests the
truth value of these functions will still work the same way.
And convert some
return (foo);
to
return foo;
Signed-off-by: NeilBrown <neilb@suse.com>
---
fs/locks.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 49 insertions(+), 15 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index b4812da2a374..d06658b2dc7a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -139,6 +139,16 @@
#define IS_OFDLCK(fl) (fl->fl_flags & FL_OFDLCK)
#define IS_REMOTELCK(fl) (fl->fl_pid <= 0)
+/* A transitive conflict is one where the first lock conflicts with
+ * the second lock, and any other lock that conflicts with the
+ * first lock, also conflicts with the second lock.
+ */
+enum conflict {
+ FL_NO_CONFLICT = 0,
+ FL_CONFLICT,
+ FL_TRANSITIVE_CONFLICT,
+};
+
static inline bool is_remote_lock(struct file *filp)
{
return likely(!(filp->f_path.dentry->d_sb->s_flags & SB_NOREMOTELOCK));
@@ -612,6 +622,15 @@ static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
(fl2->fl_end >= fl1->fl_start));
}
+/* Check for transitive-overlap - true if any lock that overlaps
+ * the first lock must overlap the seconds
+ */
+static inline bool locks_transitive_overlap(struct file_lock *fl1,
+ struct file_lock *fl2)
+{
+ return (fl1->fl_start >= fl2->fl_start) &&
+ (fl1->fl_end <= fl2->fl_end);
+}
/*
* Check whether two locks have the same owner.
*/
@@ -793,47 +812,61 @@ locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose)
/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
* checks for shared/exclusive status of overlapping locks.
*/
-static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+static enum conflict locks_conflict(struct file_lock *caller_fl,
+ struct file_lock *sys_fl)
{
if (sys_fl->fl_type == F_WRLCK)
- return 1;
+ return FL_TRANSITIVE_CONFLICT;
if (caller_fl->fl_type == F_WRLCK)
- return 1;
- return 0;
+ return FL_CONFLICT;
+ return FL_NO_CONFLICT;
}
/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
* checking before calling the locks_conflict().
*/
-static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+static enum conflict posix_locks_conflict(struct file_lock *caller_fl,
+ struct file_lock *sys_fl)
{
/* POSIX locks owned by the same process do not conflict with
* each other.
*/
if (posix_same_owner(caller_fl, sys_fl))
- return (0);
+ return FL_NO_CONFLICT;
/* Check whether they overlap */
if (!locks_overlap(caller_fl, sys_fl))
- return 0;
+ return FL_NO_CONFLICT;
- return (locks_conflict(caller_fl, sys_fl));
+ switch (locks_conflict(caller_fl, sys_fl)) {
+ default:
+ case FL_NO_CONFLICT:
+ return FL_NO_CONFLICT;
+ case FL_CONFLICT:
+ return FL_CONFLICT;
+ case FL_TRANSITIVE_CONFLICT:
+ if (locks_transitive_overlap(caller_fl, sys_fl))
+ return FL_TRANSITIVE_CONFLICT;
+ else
+ return FL_CONFLICT;
+ }
}
/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
* checking before calling the locks_conflict().
*/
-static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+static enum conflict flock_locks_conflict(struct file_lock *caller_fl,
+ struct file_lock *sys_fl)
{
/* FLOCK locks referring to the same filp do not conflict with
* each other.
*/
if (caller_fl->fl_file == sys_fl->fl_file)
- return (0);
+ return FL_NO_CONFLICT;
if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
- return 0;
+ return FL_NO_CONFLICT;
- return (locks_conflict(caller_fl, sys_fl));
+ return locks_conflict(caller_fl, sys_fl);
}
void
@@ -1435,12 +1468,13 @@ static void time_out_leases(struct inode *inode, struct list_head *dispose)
}
}
-static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker)
+static enum conflict leases_conflict(struct file_lock *lease,
+ struct file_lock *breaker)
{
if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT))
- return false;
+ return FL_NO_CONFLICT;
if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE))
- return false;
+ return FL_NO_CONFLICT;
return locks_conflict(breaker, lease);
}
next prev parent reply other threads:[~2018-08-09 2:07 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-09 2:04 [PATCH 0/5 - V2] locks: avoid thundering-herd wake-ups NeilBrown
2018-08-09 2:04 ` [PATCH 1/5] fs/locks: rename some lists and pointers NeilBrown
2018-08-09 2:04 ` [PATCH 2/5] fs/locks: allow a lock request to block other requests NeilBrown
2018-08-09 2:04 ` NeilBrown [this message]
2018-08-09 11:09 ` [PATCH 3/5] fs/locks: change all *_conflict() functions to return a new enum Jeff Layton
2018-08-09 13:09 ` J. Bruce Fields
2018-08-09 23:40 ` NeilBrown
2018-08-10 0:56 ` J. Bruce Fields
2018-08-09 2:04 ` [PATCH 4/5] fs/locks: split out __locks_wake_one() NeilBrown
2018-08-09 2:04 ` [PATCH 5/5] fs/locks: create a tree of dependent requests NeilBrown
2018-08-09 11:17 ` Jeff Layton
2018-08-09 23:25 ` NeilBrown
2018-08-09 14:13 ` J. Bruce Fields
2018-08-09 22:19 ` NeilBrown
2018-08-10 0:36 ` J. Bruce Fields
2018-08-09 17:32 ` [PATCH 0/5 - V2] locks: avoid thundering-herd wake-ups J. Bruce Fields
2018-08-09 22:12 ` NeilBrown
2018-08-10 0:29 ` J. Bruce Fields
2018-08-10 1:50 ` NeilBrown
2018-08-10 2:52 ` J. Bruce Fields
2018-08-10 3:17 ` NeilBrown
2018-08-10 15:47 ` J. Bruce Fields
2018-08-11 11:56 ` Jeff Layton
2018-08-11 12:35 ` J. Bruce Fields
2018-08-11 11:51 ` Jeff Layton
2018-08-11 12:21 ` J. Bruce Fields
2018-08-11 13:15 ` Jeff Layton
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