f2fs: add new ioctl F2FS_IOC_GARBAGE_COLLECT

When background gc is off, the only way to trigger gc is executing
a force gc in some operations who wants to grab space in disk.

The executing condition is limited: to execute force gc, we should
wait for the time when there is almost no more free section for LFS
allocation. This seems not reasonable for our user who wants to
control triggering gc by himself.

This patch introduces F2FS_IOC_GARBAGE_COLLECT interface for
triggering garbage collection by using ioctl. It provides our users
one more option to trigger gc.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -228,6 +228,7 @@ static inline bool __has_cursum_space(struct f2fs_summary_block *sum, int size,
 #define F2FS_IOC_START_VOLATILE_WRITE	_IO(F2FS_IOCTL_MAGIC, 3)
 #define F2FS_IOC_RELEASE_VOLATILE_WRITE	_IO(F2FS_IOCTL_MAGIC, 4)
 #define F2FS_IOC_ABORT_VOLATILE_WRITE	_IO(F2FS_IOCTL_MAGIC, 5)
+#define F2FS_IOC_GARBAGE_COLLECT	_IO(F2FS_IOCTL_MAGIC, 6)
 
 #define F2FS_IOC_SET_ENCRYPTION_POLICY					\
 		_IOR('f', 19, struct f2fs_encryption_policy)

fs/f2fs/file.c

@@ -27,6 +27,7 @@
 #include "segment.h"
 #include "xattr.h"
 #include "acl.h"
+#include "gc.h"
 #include "trace.h"
 #include <trace/events/f2fs.h>
 
@@ -1558,6 +1559,35 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
 	return 0;
 }
 
+static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	__u32 i, count;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (get_user(count, (__u32 __user *)arg))
+		return -EFAULT;
+
+	if (!count || count > F2FS_BATCH_GC_MAX_NUM)
+		return -EINVAL;
+
+	for (i = 0; i < count; i++) {
+		if (!mutex_trylock(&sbi->gc_mutex))
+			break;
+
+		if (f2fs_gc(sbi))
+			break;
+	}
+
+	if (put_user(i, (__u32 __user *)arg))
+		return -EFAULT;
+
+	return 0;
+}
+
 long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	switch (cmd) {
@@ -1587,6 +1617,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return f2fs_ioc_get_encryption_policy(filp, arg);
 	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
 		return f2fs_ioc_get_encryption_pwsalt(filp, arg);
+	case F2FS_IOC_GARBAGE_COLLECT:
+		return f2fs_ioc_gc(filp, arg);
 	default:
 		return -ENOTTY;
 	}

fs/f2fs/gc.h

@@ -19,6 +19,12 @@
 #define LIMIT_INVALID_BLOCK	40 /* percentage over total user space */
 #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
 
+/*
+ * with this macro, we can control the max time we do garbage collection,
+ * when user triggers batch mode gc by ioctl.
+ */
+#define F2FS_BATCH_GC_MAX_NUM		16
+
 /* Search max. number of dirty segments to select a victim segment */
 #define DEF_MAX_VICTIM_SEARCH 4096 /* covers 8GB */