From ce08b62d18b3f97cd4e5a39bd5898872b9201875 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sat, 11 Jan 2014 19:19:53 +0100 Subject: [PATCH] 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 Signed-off-by: Al Viro --- fs/file.c | 26 +++++++++----------------- 1 file 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); -- 2.39.5