[PATCH 1/2] btrfs: Make btrfs_start_delalloc_root's nr argument a long

[Nikolay Borisov <nborisov@suse.com>]

It's currently u64 which gets instantly translated either to LONG_MAX
(if U64_MAX is passed) or casted to an unsigned long (which is in fact,
wrong because iwriteback_control::nr_to_write is a signed, long type).

Just convert the function's argument to be long time which obviates the
need to manually convert u64 value to a long. Adjust all call sites
which pass U64_MAX to pass LONG_MAX. Finally ensure that in
shrink_delalloc the u64 is converted to a long without overflowing,
resulting in a negative number.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
David,

Here are 2 patches which I believe should be folded into
"btrfs: shrink delalloc pages instead of full inodes" so as to avoid needless
casts and a possible overflow, resulting in negative nr_to_write value.

 fs/btrfs/ctree.h       | 2 +-
 fs/btrfs/dev-replace.c | 2 +-
 fs/btrfs/inode.c       | 6 +++---
 fs/btrfs/ioctl.c       | 2 +-
 fs/btrfs/space-info.c  | 3 ++-
 5 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 05f009fbbd55..3dc67f241919 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3101,7 +3101,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 			       u32 min_type);

 int btrfs_start_delalloc_snapshot(struct btrfs_root *root);
-int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, u64 nr,
+int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, long nr,
 			       bool in_reclaim_context);
 int btrfs_set_extent_delalloc(struct btrfs_inode *inode, u64 start, u64 end,
 			      unsigned int extra_bits,
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 324f646d6e5e..bc73f798ce3a 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -715,7 +715,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 	 * flush all outstanding I/O and inode extent mappings before the
 	 * copy operation is declared as being finished
 	 */
-	ret = btrfs_start_delalloc_roots(fs_info, U64_MAX, false);
+	ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
 	if (ret) {
 		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 		return ret;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5c173a30a97a..69e24341afc0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9474,11 +9474,11 @@ int btrfs_start_delalloc_snapshot(struct btrfs_root *root)
 	return start_delalloc_inodes(root, &wbc, true, false);
 }

-int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, u64 nr,
+int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, long nr,
 			       bool in_reclaim_context)
 {
 	struct writeback_control wbc = {
-		.nr_to_write = (nr == U64_MAX) ? LONG_MAX : (unsigned long)nr,
+		.nr_to_write = nr,
 		.sync_mode = WB_SYNC_NONE,
 		.range_start = 0,
 		.range_end = LLONG_MAX,
@@ -9500,7 +9500,7 @@ int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, u64 nr,
 		 * Reset nr_to_write here so we know that we're doing a full
 		 * flush.
 		 */
-		if (nr == U64_MAX)
+		if (nr == LONG_MAX)
 			wbc.nr_to_write = LONG_MAX;

 		root = list_first_entry(&splice, struct btrfs_root,
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index db29c1b54daa..998ea561d934 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4973,7 +4973,7 @@ long btrfs_ioctl(struct file *file, unsigned int
 	case BTRFS_IOC_SYNC: {
 		int ret;

-		ret = btrfs_start_delalloc_roots(fs_info, U64_MAX, false);
+		ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
 		if (ret)
 			return ret;
 		ret = btrfs_sync_fs(inode->i_sb, 1);
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index e8347461c8dd..84fb94e78a8f 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -532,7 +532,8 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info,

 	loops = 0;
 	while ((delalloc_bytes || dio_bytes) && loops < 3) {
-		u64 nr_pages = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;
+		u64 temp = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;
+		long nr_pages = min_t(u64, temp, LONG_MAX);

 		btrfs_start_delalloc_roots(fs_info, nr_pages, true);

--
2.25.1