diff options
authorAl Viro <viro@zeniv.linux.org.uk>2010-05-26 15:13:55 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2010-05-27 22:03:07 -0400
commitd7065da038227a4d09a244e6014e0186a6bd21d0 (patch)
parent176306f59ac7a35369cbba87aff13e14c5916074 (diff)
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: Al Viro <viro@zeniv.linux.org.uk>
4 files changed, 14 insertions, 15 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 48fdeebdb544..1ccf25cef1f0 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -527,7 +527,7 @@ static void aio_fput_routine(struct work_struct *data)
/* Complete the fput(s) */
if (req->ki_filp != NULL)
- __fput(req->ki_filp);
+ fput(req->ki_filp);
/* 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);
diff --git a/fs/file_table.c b/fs/file_table.c
index 32d12b78bac8..5c7d10ead4ad 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -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))
- __fput(file);
* 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))
+ __fput(file);
struct file *fget(unsigned int fd)
struct file *file;
diff --git a/include/linux/file.h b/include/linux/file.h
index 5555508fd517..b1e12970f617 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -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);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 85e823adcd4a..3d9ed8302402 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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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