[PATCH v3 1/3] iomap: pass blocksize to iomap_truncate_page()

[Zhang Yi <yi.zhang@xxxxxxxxxxxxxxx>]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

iomap_truncate_page() always assumes the block size of the truncating
inode is i_blocksize(), this is not always true for some filesystems,
e.g. XFS does extent size alignment for realtime inodes. Drop this
assumption and pass the block size for zeroing into
iomap_truncate_page(), allow filesystems to indicate the correct block
size.

Suggested-by: Dave Chinner <david@xxxxxxxxxxxxx>
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
 fs/iomap/buffered-io.c | 13 +++++++++----
 fs/xfs/xfs_iomap.c     |  3 ++-
 include/linux/iomap.h  |  4 ++--
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 0926d216a5af..a0a0ac2c659c 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -17,6 +17,7 @@
 #include <linux/bio.h>
 #include <linux/sched/signal.h>
 #include <linux/migrate.h>
+#include <linux/math64.h>
 #include "trace.h"
 
 #include "../internal.h"
@@ -1445,11 +1446,15 @@ iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 EXPORT_SYMBOL_GPL(iomap_zero_range);
 
 int
-iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
-		const struct iomap_ops *ops)
+iomap_truncate_page(struct inode *inode, loff_t pos, unsigned int blocksize,
+		bool *did_zero, const struct iomap_ops *ops)
 {
-	unsigned int blocksize = i_blocksize(inode);
-	unsigned int off = pos & (blocksize - 1);
+	unsigned int off;
+
+	if (is_power_of_2(blocksize))
+		off = pos & (blocksize - 1);
+	else
+		div_u64_rem(pos, blocksize, &off);
 
 	/* Block boundary? Nothing to do */
 	if (!off)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 2857ef1b0272..31ac07bb8425 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1467,10 +1467,11 @@ xfs_truncate_page(
 	bool			*did_zero)
 {
 	struct inode		*inode = VFS_I(ip);
+	unsigned int		blocksize = i_blocksize(inode);
 
 	if (IS_DAX(inode))
 		return dax_truncate_page(inode, pos, did_zero,
 					&xfs_dax_write_iomap_ops);
-	return iomap_truncate_page(inode, pos, did_zero,
+	return iomap_truncate_page(inode, pos, blocksize, did_zero,
 				   &xfs_buffered_write_iomap_ops);
 }
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 6fc1c858013d..d67bf86ec582 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -273,8 +273,8 @@ int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
 		const struct iomap_ops *ops);
 int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
 		bool *did_zero, const struct iomap_ops *ops);
-int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
-		const struct iomap_ops *ops);
+int iomap_truncate_page(struct inode *inode, loff_t pos, unsigned int blocksize,
+		bool *did_zero, const struct iomap_ops *ops);
 vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf,
 			const struct iomap_ops *ops);
 int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
-- 
2.39.2