5.10-stable review patch. If anyone has any objections, please let me know.
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From: Eric W. Biederman ebiederm@xmission.com
[ Upstream commit 64eb661fda0269276b4c46965832938e3f268268 ]
When discussing[1] exec and posix file locks it was realized that none of the callers of get_files_struct fundamentally needed to call get_files_struct, and that by switching them to helper functions instead it will both simplify their code and remove unnecessary increments of files_struct.count. Those unnecessary increments can result in exec unnecessarily unsharing files_struct which breaking posix locks, and it can result in fget_light having to fallback to fget reducing system performance.
Instead of manually coding finding the files struct for a task and then calling files_lookup_fd_rcu, use the helper task_lookup_fd_rcu that combines those to steps. Making the code simpler and removing the need to get a reference on a files_struct.
[1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com Suggested-by: Oleg Nesterov oleg@redhat.com Acked-by: Christian Brauner christian.brauner@ubuntu.com v1: https://lkml.kernel.org/r/20200817220425.9389-7-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-12-ebiederm@xmission.com Signed-off-by: Eric W. Biederman ebiederm@xmission.com Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/fd.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 3dec44d7c5c5c..c1a984f3c4df7 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -83,18 +83,13 @@ static const struct file_operations proc_fdinfo_file_operations = {
static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode) { - struct files_struct *files = get_files_struct(task); struct file *file;
- if (!files) - return false; - rcu_read_lock(); - file = files_lookup_fd_rcu(files, fd); + file = task_lookup_fd_rcu(task, fd); if (file) *mode = file->f_mode; rcu_read_unlock(); - put_files_struct(files); return !!file; }