Pollable asynchronous fsync() using a global workqueue. Maybe a sync_file_range
in the future.
Signed-off-by: Davi E. M. Arnaut <[EMAIL PROTECTED]>
---
Index: linux-2.6/fs/pollfs/Makefile
===================================================================
--- linux-2.6.orig/fs/pollfs/Makefile
+++ linux-2.6/fs/pollfs/Makefile
@@ -5,3 +5,4 @@ pollfs-$(CONFIG_POLLFS_SIGNAL) += signal
pollfs-$(CONFIG_POLLFS_TIMER) += timer.o
pollfs-$(CONFIG_POLLFS_FUTEX) += futex.o
pollfs-$(CONFIG_POLLFS_AIO) += aio.o
+pollfs-$(CONFIG_POLLFS_SYNC) += sync.o
Index: linux-2.6/fs/pollfs/sync.c
===================================================================
--- /dev/null
+++ linux-2.6/fs/pollfs/sync.c
@@ -0,0 +1,173 @@
+/*
+ * pollable fsync
+ *
+ * Copyright (C) 2007 Davi E. M. Arnaut
+ *
+ * Licensed under the GNU GPL. See the file COPYING for details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/wait.h>
+#include <linux/poll.h>
+#include <linux/pollfs_fs.h>
+#include <linux/workqueue.h>
+#include <linux/file.h>
+
+struct sync_file {
+ int fd;
+ int datasync;
+ long result;
+};
+
+struct pfs_sync {
+ struct file *filp;
+ struct sync_file sync;
+ struct work_struct work;
+ struct mutex mutex;
+ enum {
+ WORK_REST,
+ WORK_BUSY,
+ WORK_DONE,
+ } status;
+ wait_queue_head_t wait;
+ struct pfs_file file;
+};
+
+static struct workqueue_struct *sync_wq;
+
+static void sync_file_work(struct work_struct *work)
+{
+ struct pfs_sync *evs = container_of(work, struct pfs_sync, work);
+
+ evs->sync.result = do_fsync(evs->filp, evs->sync.datasync);
+
+ fput(evs->filp);
+ evs->status = WORK_DONE;
+
+ wake_up_all(&evs->wait);
+}
+
+static ssize_t read(struct pfs_sync *evs, struct sync_file __user *usync)
+{
+ int ret = 0;
+ struct sync_file sync = {};
+
+ mutex_lock(&evs->mutex);
+ switch (evs->status) {
+ case WORK_REST:
+ ret = -EINVAL; break;
+ case WORK_BUSY:
+ ret = -EAGAIN; break;
+ case WORK_DONE:
+ evs->status = WORK_REST;
+ sync = evs->sync;
+ break;
+ }
+ mutex_unlock(&evs->mutex);
+
+ if (ret)
+ return ret;
+
+ if (copy_to_user(usync, &sync, sizeof(sync)))
+ return -EFAULT;
+
+ return 0;
+}
+
+static ssize_t write(struct pfs_sync *evs, const struct sync_file __user
*usync)
+{
+ int ret = 0;
+ struct file *filp;
+ struct sync_file sync;
+
+ if (copy_from_user(&sync, usync, sizeof(sync)))
+ return -EFAULT;
+
+ filp = fget(sync.fd);
+ if (!filp)
+ return -EINVAL;
+
+ mutex_lock(&evs->mutex);
+ if (evs->status != WORK_REST)
+ ret = -EAGAIN;
+ else {
+ evs->filp = filp;
+ evs->status = WORK_BUSY;
+ queue_async_work(sync_wq, &evs->work);
+ }
+ mutex_unlock(&evs->mutex);
+
+ return ret;
+}
+
+static int poll(struct pfs_sync *evs)
+{
+ int ret = 0;
+
+ if (evs->status == WORK_DONE)
+ ret = POLLIN;
+ else if (evs->status == WORK_REST)
+ ret = POLLOUT;
+
+ return ret;
+}
+
+static int release(struct pfs_sync *evs)
+{
+ wait_event(evs->wait, evs->status != WORK_BUSY);
+
+ kfree(evs);
+
+ return 0;
+}
+
+static const struct pfs_operations sync_ops = {
+ .read = PFS_READ(read, struct pfs_sync, struct sync_file),
+ .write = PFS_WRITE(write, struct pfs_sync, struct sync_file),
+ .poll = PFS_POLL(poll, struct pfs_sync),
+ .release = PFS_RELEASE(release, struct pfs_sync),
+ .rsize = sizeof(struct sync_file),
+ .wsize = sizeof(struct sync_file),
+};
+
+asmlinkage long sys_plsync(void)
+{
+ long error;
+ struct pfs_sync *evs;
+
+ if (!sync_wq)
+ return -ENOSYS;
+
+ evs = kzalloc(sizeof(*evs), GFP_KERNEL);
+ if (!evs)
+ return -ENOMEM;
+
+ evs->status = WORK_REST;
+ mutex_init(&evs->mutex);
+ init_waitqueue_head(&evs->wait);
+ INIT_WORK(&evs->work, sync_file_work);
+
+ evs->file.data = evs;
+ evs->file.fops = &sync_ops;
+ evs->file.wait = &evs->wait;
+
+ error = pfs_open(&evs->file);
+
+ if (error < 0)
+ release(evs);
+
+ return error;
+}
+
+static int __init init(void)
+{
+ sync_wq = create_workqueue("syncd");
+ WARN_ON(!sync_wq);
+ return 0;
+}
+
+__initcall(init);
Index: linux-2.6/init/Kconfig
===================================================================
--- linux-2.6.orig/init/Kconfig
+++ linux-2.6/init/Kconfig
@@ -497,6 +497,13 @@ config POLLFS_AIO
help
Pollable aio support
+config POLLFS_SYNC
+ bool "Enable pollfs file sync" if EMBEDDED
+ default y
+ depends on POLLFS
+ help
+ Pollable file sync support
+
config SHMEM
bool "Use full shmem filesystem" if EMBEDDED
default y
--
-
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