[PATCH] f2fs: separate NOCoW and pinfile semantics

[Chao Yu]

Pinning a file is heavy, because skipping pinned files make GC
running with heavy load or no effect.

So that this patch propose to separate nocow and pinfile semantics:
- NOCoW flag can only be set on regular file.
- NOCoW file will only trigger IPU at common writeback/flush.
- NOCow file will do OPU during GC.

For the demand of 1) avoid fragment of file's physical block and
2) userspace don't care about file's specific physical address,
tagging file as NOCoW will be cheaper than pinned one.

Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
 fs/f2fs/data.c |  3 ++-
 fs/f2fs/f2fs.h |  1 +
 fs/f2fs/file.c | 20 +++++++++++++++++---
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index a2a28bb269bf..15fb8954c363 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1884,7 +1884,8 @@ static inline bool check_inplace_update_policy(struct inode *inode,
 
 bool f2fs_should_update_inplace(struct inode *inode, struct f2fs_io_info *fio)
 {
-	if (f2fs_is_pinned_file(inode))
+	if (f2fs_is_pinned_file(inode) ||
+			F2FS_I(inode)->i_flags & F2FS_NOCOW_FL)
 		return true;
 
 	/* if this is cold file, we should overwrite to avoid fragmentation */
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 596ab3e1dd7b..f6c5a3d2e659 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2374,6 +2374,7 @@ static inline void f2fs_change_bit(unsigned int nr, char *addr)
 #define F2FS_NOATIME_FL			0x00000080 /* do not update atime */
 #define F2FS_INDEX_FL			0x00001000 /* hash-indexed directory */
 #define F2FS_DIRSYNC_FL			0x00010000 /* dirsync behaviour (directories only) */
+#define F2FS_NOCOW_FL			0x00800000 /* Do not cow file */
 #define F2FS_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
 
 /* Flags that should be inherited by new inodes from their parent. */
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 7ca545874060..ed6556f4cba7 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1659,6 +1659,20 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
 	if (IS_NOQUOTA(inode))
 		return -EPERM;
 
+	if ((iflags ^ oldflags) & F2FS_NOCOW_FL) {
+		int err;
+
+		if (!S_ISREG(inode->i_mode))
+			return -EINVAL;
+
+		if (f2fs_should_update_outplace(inode, NULL))
+			return -EINVAL;
+
+		err = f2fs_convert_inline_inode(inode);
+		if (err)
+			return err;
+	}
+
 	fi->i_flags = iflags | (fi->i_flags & ~mask);
 
 	if (fi->i_flags & F2FS_PROJINHERIT_FL)
@@ -1692,6 +1706,7 @@ static const struct {
 	{ F2FS_NOATIME_FL,	FS_NOATIME_FL },
 	{ F2FS_INDEX_FL,	FS_INDEX_FL },
 	{ F2FS_DIRSYNC_FL,	FS_DIRSYNC_FL },
+	{ F2FS_NOCOW_FL,	FS_NOCOW_FL },
 	{ F2FS_PROJINHERIT_FL,	FS_PROJINHERIT_FL },
 };
 
@@ -1715,7 +1730,8 @@ static const struct {
 		FS_NODUMP_FL |		\
 		FS_NOATIME_FL |		\
 		FS_DIRSYNC_FL |		\
-		FS_PROJINHERIT_FL)
+		FS_PROJINHERIT_FL |	\
+		FS_NOCOW_FL)
 
 /* Convert f2fs on-disk i_flags to FS_IOC_{GET,SET}FLAGS flags */
 static inline u32 f2fs_iflags_to_fsflags(u32 iflags)
@@ -1753,8 +1769,6 @@ static int f2fs_ioc_getflags(struct file *filp, unsigned long arg)
 		fsflags |= FS_ENCRYPT_FL;
 	if (f2fs_has_inline_data(inode) || f2fs_has_inline_dentry(inode))
 		fsflags |= FS_INLINE_DATA_FL;
-	if (is_inode_flag_set(inode, FI_PIN_FILE))
-		fsflags |= FS_NOCOW_FL;
 
 	fsflags &= F2FS_GETTABLE_FS_FL;
 
-- 
2.18.0.rc1