[PATCH] f2fs: fix defragment writeback range truncation on 32-bit

[PATCH] f2fs: fix defragment writeback range truncation on 32-bit

[Zhan Xusheng]

f2fs_defragment_range() flushes the range it is about to defragment:

	filemap_write_and_wait_range(inode->i_mapping,
				pg_start << PAGE_SHIFT,
				(pg_end << PAGE_SHIFT) - 1);

pg_start and pg_end are pgoff_t, 32 bits on 32-bit kernels, so both
shifts are evaluated in 32 bits and truncated before they are widened to
the loff_t parameters.  pg_end is only capped by the file's page count,
so for a file larger than 4 GiB the shift wraps.

For a 5 GiB file pg_end is 1310720 and the range collapses from
[0, 5 GiB) to [0, 1 GiB), leaving the rest of the dirty pages unwritten
before the blocks are moved.  For 8 GiB the shift yields 0, the minus one
makes it (loff_t)-1, and the range becomes [0, LLONG_MAX].

The matching call in f2fs_collapse_range() already casts:

	filemap_write_and_wait_range(inode->i_mapping,
				(loff_t)index << PAGE_SHIFT,
				((loff_t)pg_end << PAGE_SHIFT) - 1);

Do the same here.  On i386 the shift changes from "shl $0xc,%ecx" to
"shld", i.e. from a 32-bit shift to a double-precision one.

Fixes: d323d005ac4a ("f2fs: support file defragment")
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
---
 fs/f2fs/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index ef4d218e694b..0d9919d89d93 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3036,8 +3036,8 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
 
 	/* writeback all dirty pages in the range */
 	err = filemap_write_and_wait_range(inode->i_mapping,
-						pg_start << PAGE_SHIFT,
-						(pg_end << PAGE_SHIFT) - 1);
+						(loff_t)pg_start << PAGE_SHIFT,
+						((loff_t)pg_end << PAGE_SHIFT) - 1);
 	if (err)
 		goto out;
 

base-commit: caae4bfcf5b5794fdf6299eb6c4fbf3d149db000
-- 
2.43.0