[PATCH 2/3] bcachefs: Refactor the handling logic of fallocate mode in bch2_fallocate_dispatch()

[Youling Tang <youling.tang@linux.dev>]

From: Youling Tang <tangyouling@kylinos.cn>

The mode parameter of the fallocate system call is divided into exclusive
mode (FALLOC_FL_MODE_MASK) and optional flag (FALLOC_FL_KEEP_SIZE).

Use FALLOC_FL_MODE_MASK and FALLOC_FL_ALLOCATE_RANGE makes the code more
readable.

Some of the logic has been handled in vfs_fallocate:
- FALLOC_FL_PUNCH_HOLE must exist simultaneously with FALLOC_FL_KEEP_SIZE.
- FALLOC_FL_COLLAPSE_RANGE and FALLOC_FL_INSERT_RANGE cannot exist
  simultaneously with FALLOC_FL_KEEP_SIZE.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 fs/bcachefs/fs-io.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/fs/bcachefs/fs-io.c b/fs/bcachefs/fs-io.c
index 74841b1dc8ca..69d3ddd4c6a1 100644
--- a/fs/bcachefs/fs-io.c
+++ b/fs/bcachefs/fs-io.c
@@ -814,6 +814,12 @@ static noinline long bchfs_fallocate(struct bch_inode_info *inode, int mode,
 	return ret ?: ret2;
 }
 
+#define BCH2_FALLOC_FL_SUPPORTED					\
+		(FALLOC_FL_KEEP_SIZE |					\
+		 FALLOC_FL_ALLOCATE_RANGE | FALLOC_FL_PUNCH_HOLE |	\
+		 FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |	\
+		 FALLOC_FL_INSERT_RANGE)
+
 long bch2_fallocate_dispatch(struct file *file, int mode,
 			     loff_t offset, loff_t len)
 {
@@ -824,6 +830,9 @@ long bch2_fallocate_dispatch(struct file *file, int mode,
 	if (!enumerated_ref_tryget(&c->writes, BCH_WRITE_REF_fallocate))
 		return -EROFS;
 
+	if (mode & ~BCH2_FALLOC_FL_SUPPORTED)
+		return bch2_err_class(bch_err_throw(c, unsupported_fallocate_mode));
+
 	inode_lock(&inode->v);
 	inode_dio_wait(&inode->v);
 	bch2_pagecache_block_get(inode);
@@ -832,16 +841,24 @@ long bch2_fallocate_dispatch(struct file *file, int mode,
 	if (ret)
 		goto err;
 
-	if (!(mode & ~(FALLOC_FL_KEEP_SIZE|FALLOC_FL_ZERO_RANGE)))
+	switch (mode & FALLOC_FL_MODE_MASK) {
+	case FALLOC_FL_ALLOCATE_RANGE:
+	case FALLOC_FL_ZERO_RANGE:
 		ret = bchfs_fallocate(inode, mode, offset, len);
-	else if (mode == (FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE))
+		break;
+	case FALLOC_FL_PUNCH_HOLE:
 		ret = bchfs_fpunch(inode, offset, len);
-	else if (mode == FALLOC_FL_INSERT_RANGE)
+		break;
+	case FALLOC_FL_INSERT_RANGE:
 		ret = bchfs_fcollapse_finsert(inode, offset, len, true);
-	else if (mode == FALLOC_FL_COLLAPSE_RANGE)
+		break;
+	case FALLOC_FL_COLLAPSE_RANGE:
 		ret = bchfs_fcollapse_finsert(inode, offset, len, false);
-	else
+		break;
+	default:
 		ret = bch_err_throw(c, unsupported_fallocate_mode);
+		break;
+	}
 err:
 	bch2_pagecache_block_put(inode);
 	inode_unlock(&inode->v);
-- 
2.34.1