Commit d7065da0 authored by Al Viro's avatar Al Viro

get rid of the magic around f_count in aio

__aio_put_req() plays sick games with file refcount.  What
it wants is fput() from atomic context; it's almost always
done with f_count > 1, so they only have to deal with delayed
work in rare cases when their reference happens to be the
last one.  Current code decrements f_count and if it hasn't
hit 0, everything is fine.  Otherwise it keeps a pointer
to struct file (with zero f_count!) around and has delayed
work do __fput() on it.

Better way to do it: use atomic_long_add_unless( , -1, 1)
instead of !atomic_long_dec_and_test().  IOW, decrement it
only if it's not the last reference, leave refcount alone
if it was.  And use normal fput() in delayed work.

I've made that atomic_long_add_unless call a new helper -
fput_atomic().  Drops a reference to file if it's safe to
do in atomic (i.e. if that's not the last one), tells if
it had been able to do that.  aio.c converted to it, __fput()
use is gone.  req->ki_file *always* contributes to refcount
now.  And __fput() became static.
Signed-off-by: default avatarAl Viro <>
parent 176306f5
......@@ -527,7 +527,7 @@ static void aio_fput_routine(struct work_struct *data)
/* Complete the fput(s) */
if (req->ki_filp != NULL)
/* Link the iocb into the context's free list */
......@@ -560,11 +560,11 @@ static int __aio_put_req(struct kioctx *ctx, struct kiocb *req)
* Try to optimize the aio and eventfd file* puts, by avoiding to
* schedule work in case it is not __fput() time. In normal cases,
* schedule work in case it is not final fput() time. In normal cases,
* we would not be holding the last reference to the file*, so
* this function will be executed w/out any aio kthread wakeup.
if (unlikely(atomic_long_dec_and_test(&req->ki_filp->f_count))) {
if (unlikely(!fput_atomic(req->ki_filp))) {
list_add(&req->ki_list, &fput_head);
......@@ -194,14 +194,6 @@ struct file *alloc_file(struct path *path, fmode_t mode,
void fput(struct file *file)
if (atomic_long_dec_and_test(&file->f_count))
* drop_file_write_access - give up ability to write to a file
* @file: the file to which we will stop writing
......@@ -227,10 +219,9 @@ void drop_file_write_access(struct file *file)
/* __fput is called from task context when aio completion releases the last
* last use of a struct file *. Do not use otherwise.
/* the real guts of fput() - releasing the last reference to file
void __fput(struct file *file)
static void __fput(struct file *file)
struct dentry *dentry = file->f_path.dentry;
struct vfsmount *mnt = file->f_path.mnt;
......@@ -268,6 +259,14 @@ void __fput(struct file *file)
void fput(struct file *file)
if (atomic_long_dec_and_test(&file->f_count))
struct file *fget(unsigned int fd)
struct file *file;
......@@ -11,7 +11,6 @@
struct file;
extern void __fput(struct file *);
extern void fput(struct file *);
extern void drop_file_write_access(struct file *file);
......@@ -954,6 +954,7 @@ extern spinlock_t files_lock;
#define file_list_unlock() spin_unlock(&files_lock);
#define get_file(x) atomic_long_inc(&(x)->f_count)
#define fput_atomic(x) atomic_long_add_unless(&(x)->f_count, -1, 1)
#define file_count(x) atomic_long_read(&(x)->f_count)
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