Once upon a time, predecessors of those used to do file lookup
without bumping a refcount, provided that caller held rcu_read_lock()
across the lookup and whatever it wanted to read from the struct
file found. When struct file allocation switched to SLAB_TYPESAFE_BY_RCU,
that stopped being feasible and these primitives started to bump the
file refcount for lookup result, requiring the caller to call fput()
afterwards.
But that turned them pointless - e.g.
rcu_read_lock();
file = lookup_fdget_rcu(fd);
rcu_read_unlock();
is equivalent to
file = fget_raw(fd);
and all callers of lookup_fdget_rcu() are of that form. Similarly,
task_lookup_fdget_rcu() calls can be replaced with calling fget_task().
task_lookup_next_fdget_rcu() doesn't have direct counterparts, but
its callers would be happier if we replaced it with an analogue that
deals with RCU internally.
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/platforms/cell/spufs/coredump.c | 4 +--
fs/file.c | 28 +++-----------------
fs/gfs2/glock.c | 12 ++-------
fs/notify/dnotify/dnotify.c | 5 +---
fs/proc/fd.c | 12 +++------
include/linux/fdtable.h | 4 ---
include/linux/file.h | 1 +
kernel/bpf/task_iter.c | 6 +----
kernel/kcmp.c | 4 +--
9 files changed, 14 insertions(+), 62 deletions(-)
diff --git a/arch/powerpc/platforms/cell/spufs/coredump.c b/arch/powerpc/platforms/cell/spufs/coredump.c
index 18daafbe2e65..301ee7d8b7df 100644
--- a/arch/powerpc/platforms/cell/spufs/coredump.c
+++ b/arch/powerpc/platforms/cell/spufs/coredump.c
@@ -73,9 +73,7 @@ static struct spu_context *coredump_next_context(int *fd)
return NULL;
*fd = n - 1;
- rcu_read_lock();
- file = lookup_fdget_rcu(*fd);
- rcu_read_unlock();
+ file = fget_raw(*fd);
if (file) {
ctx = SPUFS_I(file_inode(file))->i_ctx;
get_spu_context(ctx);
diff --git a/fs/file.c b/fs/file.c
index eb093e736972..991860ee7848 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1037,29 +1037,7 @@ struct file *fget_task(struct task_struct *task, unsigned int fd)
return file;
}
-struct file *lookup_fdget_rcu(unsigned int fd)
-{
- return __fget_files_rcu(current->files, fd, 0);
-
-}
-EXPORT_SYMBOL_GPL(lookup_fdget_rcu);
-
-struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd)
-{
- /* Must be called with rcu_read_lock held */
- struct files_struct *files;
- struct file *file = NULL;
-
- task_lock(task);
- files = task->files;
- if (files)
- file = __fget_files_rcu(files, fd, 0);
- task_unlock(task);
-
- return file;
-}
-
-struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *ret_fd)
+struct file *fget_task_next(struct task_struct *task, unsigned int *ret_fd)
{
/* Must be called with rcu_read_lock held */
struct files_struct *files;
@@ -1069,17 +1047,19 @@ struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *
task_lock(task);
files = task->files;
if (files) {
+ rcu_read_lock();
for (; fd < files_fdtable(files)->max_fds; fd++) {
file = __fget_files_rcu(files, fd, 0);
if (file)
break;
}
+ rcu_read_unlock();
}
task_unlock(task);
*ret_fd = fd;
return file;
}
-EXPORT_SYMBOL(task_lookup_next_fdget_rcu);
+EXPORT_SYMBOL(fget_task_next);
/*
* Lightweight file lookup - no refcnt increment if fd table isn't shared.
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 269c3bc7fced..4701c4aafbf4 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -34,7 +34,6 @@
#include <linux/lockref.h>
#include <linux/rhashtable.h>
#include <linux/pid_namespace.h>
-#include <linux/fdtable.h>
#include <linux/file.h>
#include "gfs2.h"
@@ -2768,25 +2767,18 @@ static struct file *gfs2_glockfd_next_file(struct gfs2_glockfd_iter *i)
i->file = NULL;
}
- rcu_read_lock();
for(;; i->fd++) {
- struct inode *inode;
-
- i->file = task_lookup_next_fdget_rcu(i->task, &i->fd);
+ i->file = fget_task_next(i->task, &i->fd);
if (!i->file) {
i->fd = 0;
break;
}
- inode = file_inode(i->file);
- if (inode->i_sb == i->sb)
+ if (file_inode(i->file)->i_sb == i->sb)
break;
- rcu_read_unlock();
fput(i->file);
- rcu_read_lock();
}
- rcu_read_unlock();
return i->file;
}
diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index d5dbef7f5c95..6004dfdfdf0f 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -16,7 +16,6 @@
#include <linux/security.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
-#include <linux/fdtable.h>
#include <linux/fsnotify_backend.h>
static int dir_notify_enable __read_mostly = 1;
@@ -347,9 +346,7 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned int arg)
new_fsn_mark = NULL;
}
- rcu_read_lock();
- f = lookup_fdget_rcu(fd);
- rcu_read_unlock();
+ f = fget_raw(fd);
/* if (f != filp) means that we lost a race and another task/thread
* actually closed the fd we are still playing with before we grabbed
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 1f54a54bfb91..18d0dddc8e2f 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -116,9 +116,7 @@ static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
{
struct file *file;
- rcu_read_lock();
- file = task_lookup_fdget_rcu(task, fd);
- rcu_read_unlock();
+ file = fget_task(task, fd);
if (file) {
*mode = file->f_mode;
fput(file);
@@ -258,19 +256,17 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx,
if (!dir_emit_dots(file, ctx))
goto out;
- rcu_read_lock();
for (fd = ctx->pos - 2;; fd++) {
struct file *f;
struct fd_data data;
char name[10 + 1];
unsigned int len;
- f = task_lookup_next_fdget_rcu(p, &fd);
+ f = fget_task_next(p, &fd);
ctx->pos = fd + 2LL;
if (!f)
break;
data.mode = f->f_mode;
- rcu_read_unlock();
fput(f);
data.fd = fd;
@@ -278,11 +274,9 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx,
if (!proc_fill_cache(file, ctx,
name, len, instantiate, p,
&data))
- goto out;
+ break;
cond_resched();
- rcu_read_lock();
}
- rcu_read_unlock();
out:
put_task_struct(p);
return 0;
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index b1c5722f2b3c..e25e2cb65d30 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -92,10 +92,6 @@ static inline struct file *files_lookup_fd_locked(struct files_struct *files, un
return files_lookup_fd_raw(files, fd);
}
-struct file *lookup_fdget_rcu(unsigned int fd);
-struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd);
-struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *fd);
-
static inline bool close_on_exec(unsigned int fd, const struct files_struct *files)
{
return test_bit(fd, files_fdtable(files)->close_on_exec);
diff --git a/include/linux/file.h b/include/linux/file.h
index f98de143245a..ec4ad5e6a061 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -72,6 +72,7 @@ static inline void fdput(struct fd fd)
extern struct file *fget(unsigned int fd);
extern struct file *fget_raw(unsigned int fd);
extern struct file *fget_task(struct task_struct *task, unsigned int fd);
+extern struct file *fget_task_next(struct task_struct *task, unsigned int *fd);
extern void __f_unlock_pos(struct file *);
struct fd fdget(unsigned int fd);
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index 02aa9db8d796..7fe602ca74a0 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -5,7 +5,6 @@
#include <linux/namei.h>
#include <linux/pid_namespace.h>
#include <linux/fs.h>
-#include <linux/fdtable.h>
#include <linux/filter.h>
#include <linux/bpf_mem_alloc.h>
#include <linux/btf_ids.h>
@@ -286,17 +285,14 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)
curr_fd = 0;
}
- rcu_read_lock();
- f = task_lookup_next_fdget_rcu(curr_task, &curr_fd);
+ f = fget_task_next(curr_task, &curr_fd);
if (f) {
/* set info->fd */
info->fd = curr_fd;
- rcu_read_unlock();
return f;
}
/* the current task is done, go to the next task */
- rcu_read_unlock();
put_task_struct(curr_task);
if (info->common.type == BPF_TASK_ITER_TID) {
diff --git a/kernel/kcmp.c b/kernel/kcmp.c
index b0639f21041f..2c596851f8a9 100644
--- a/kernel/kcmp.c
+++ b/kernel/kcmp.c
@@ -63,9 +63,7 @@ get_file_raw_ptr(struct task_struct *task, unsigned int idx)
{
struct file *file;
- rcu_read_lock();
- file = task_lookup_fdget_rcu(task, idx);
- rcu_read_unlock();
+ file = fget_task(task, idx);
if (file)
fput(file);
--
2.39.5
