Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/locks.c | 24 +++++++++++++++++++-----
include/linux/fs.h | 6 ++++++
2 files changed, 25 insertions(+), 5 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index e3140b8..a7d2253 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -150,6 +150,16 @@ static int target_leasetype(struct file_lock *fl)
int leases_enable = 1;
int lease_break_time = 45;
+/*
+ * The i_flock list is ordered by:
+ *
+ * 1) lock type -- FL_LEASEs first, then FL_FLOCK, and finally FL_POSIX
+ * 2) lock owner
+ * 3) lock range start
+ * 4) lock range end
+ *
+ * Obviously, the last two criteria only matter for POSIX locks.
+ */
#define for_each_lock(inode, lockp) \
for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
@@ -806,6 +816,11 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
}
lock_flocks();
+ /*
+ * New lock request. Walk all POSIX locks and look for conflicts. If
+ * there are any, either return -EAGAIN or put the request on the
+ * blocker's list of waiters.
+ */
if (request->fl_type != F_UNLCK) {
for_each_lock(inode, before) {
fl = *before;
@@ -844,7 +859,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
before = &fl->fl_next;
}
- /* Process locks with this owner. */
+ /* Process locks with this owner. */
while ((fl = *before) && posix_same_owner(request, fl)) {
/* Detect adjacent or overlapping regions (if same lock type)
*/
@@ -930,10 +945,9 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
}
/*
- * The above code only modifies existing locks in case of
- * merging or replacing. If new lock(s) need to be inserted
- * all modifications are done bellow this, so it's safe yet to
- * bail out.
+ * The above code only modifies existing locks in case of merging or
+ * replacing. If new lock(s) need to be inserted all modifications are
+ * done below this, so it's safe yet to bail out.
*/
error = -ENOLCK; /* "no luck" */
if (right && left == right && !new_fl2)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b9d7816..ae377e9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -926,6 +926,12 @@ int locks_in_grace(struct net *);
/* that will die - we need it for nfs_lock_info */
#include <linux/nfs_fs_i.h>
+/*
+ * struct file_lock represents a generic "file lock". It's used to represent
+ * POSIX byte range locks, BSD (flock) locks, and leases. It's important to
+ * note that the same struct is used to represent both a request for a lock and
+ * the lock itself, but the same object is never used for both.
+ */
struct file_lock {
struct file_lock *fl_next; /* singly linked list for this inode */
struct list_head fl_link; /* doubly linked list of all locks */
--
1.7.1
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