[PATCH 1/4] locks: don't allocate a lock context for an F_UNLCK request

From: Jeff Layton
Date: Sat Mar 07 2015 - 11:11:10 EST


In the event that we get an F_UNLCK request on an inode that has no lock
context, there is no reason to allocate one. Change
locks_get_lock_context to take a "type" pointer and avoid allocating a
new context if it's F_UNLCK.

Then, fix the callers to return appropriately if that function returns
NULL.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
---
fs/locks.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 0915a3ead897..7be49ad1c902 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -203,11 +203,11 @@ static struct kmem_cache *flctx_cache __read_mostly;
static struct kmem_cache *filelock_cache __read_mostly;

static struct file_lock_context *
-locks_get_lock_context(struct inode *inode)
+locks_get_lock_context(struct inode *inode, int type)
{
struct file_lock_context *new;

- if (likely(inode->i_flctx))
+ if (likely(inode->i_flctx) || type == F_UNLCK)
goto out;

new = kmem_cache_alloc(flctx_cache, GFP_KERNEL);
@@ -877,9 +877,12 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
bool found = false;
LIST_HEAD(dispose);

- ctx = locks_get_lock_context(inode);
- if (!ctx)
- return -ENOMEM;
+ ctx = locks_get_lock_context(inode, request->fl_type);
+ if (!ctx) {
+ if (request->fl_type != F_UNLCK)
+ return -ENOMEM;
+ return (request->fl_flags & FL_EXISTS) ? -ENOENT : 0;
+ }

if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
new_fl = locks_alloc_lock();
@@ -945,9 +948,9 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
bool added = false;
LIST_HEAD(dispose);

- ctx = locks_get_lock_context(inode);
+ ctx = locks_get_lock_context(inode, request->fl_type);
if (!ctx)
- return -ENOMEM;
+ return (request->fl_type == F_UNLCK) ? 0 : -ENOMEM;

/*
* We may need two file_lock structures for this operation,
@@ -1610,9 +1613,9 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
lease = *flp;
trace_generic_add_lease(inode, lease);

- ctx = locks_get_lock_context(inode);
+ ctx = locks_get_lock_context(inode, arg);
if (!ctx)
- return -ENOMEM;
+ return (arg == F_UNLCK) ? 0 : -ENOMEM;

/*
* In the delegation case we need mutual exclusion with
--
2.1.0

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