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authorOleg Nesterov <oleg@redhat.com>2014-01-11 19:19:53 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2014-01-25 03:14:37 -0500
commitce08b62d18b3f97cd4e5a39bd5898872b9201875 (patch)
treec5fc6f39a15131e28954cdb7fea7f8e181bc5eee
parenta8d4b8345e0ee48b732126d980efaf0dc373e2b0 (diff)
change close_files() to use rcu_dereference_raw(files->fdt)
put_files_struct() and close_files() do rcu_read_lock() to make rcu_dereference_check_fdtable() happy. This looks a bit ugly, files_fdtable() just reads the pointer, we can simply use rcu_dereference_raw() to avoid the warning. The patch also changes close_files() to return fdt, this avoids another rcu_read_lock()/files_fdtable() in put_files_struct(). I think close_files() needs more cleanups: - we do not need xchg() exactly because we are the last user of this files_struct - "if (file)" should be turned into WARN_ON(!file) Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/file.c26
1 files changed, 9 insertions, 17 deletions
diff --git a/fs/file.c b/fs/file.c
index 957cbc09b0db..d34e59e51743 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -348,21 +348,16 @@ out:
return NULL;
}
-static void close_files(struct files_struct * files)
+static struct fdtable *close_files(struct files_struct * files)
{
- int i, j;
- struct fdtable *fdt;
-
- j = 0;
-
/*
* It is safe to dereference the fd table without RCU or
* ->file_lock because this is the last reference to the
- * files structure. But use RCU to shut RCU-lockdep up.
+ * files structure.
*/
- rcu_read_lock();
- fdt = files_fdtable(files);
- rcu_read_unlock();
+ struct fdtable *fdt = rcu_dereference_raw(files->fdt);
+ int i, j = 0;
+
for (;;) {
unsigned long set;
i = j * BITS_PER_LONG;
@@ -381,6 +376,8 @@ static void close_files(struct files_struct * files)
set >>= 1;
}
}
+
+ return fdt;
}
struct files_struct *get_files_struct(struct task_struct *task)
@@ -398,14 +395,9 @@ struct files_struct *get_files_struct(struct task_struct *task)
void put_files_struct(struct files_struct *files)
{
- struct fdtable *fdt;
-
if (atomic_dec_and_test(&files->count)) {
- close_files(files);
- /* not really needed, since nobody can see us */
- rcu_read_lock();
- fdt = files_fdtable(files);
- rcu_read_unlock();
+ struct fdtable *fdt = close_files(files);
+
/* free the arrays if they are not embedded */
if (fdt != &files->fdtab)
__free_fdtable(fdt);