[PATCH v2] fs: Add uoff_t

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

In a recent commit, I inadvertently changed a comparison from being an
unsigned comparison (on 64-bit systems) to being a signed comparison
(which it had always been on 32-bit systems).  This led to a sporadic
fstests failure.

To make sure this comparison is always unsigned, introduce a new type,
uoff_t which is the unsigned version of loff_t.  Generally file sizes
are restricted to being a signed integer, but in these two places it is
convenient to pass -1 to indicate "up to the end of the file".

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---

v2: Fix build issue caused by not converting the !CONFIG_SHMEM case
With this patch and reverting b94488503277 ("iomap: use loff_t for file
positions and offsets in writeback code"), fstets passes on next-20251121

 include/linux/mm.h                     | 8 ++++----
 include/linux/shmem_fs.h               | 2 +-
 include/linux/types.h                  | 1 +
 include/uapi/asm-generic/posix_types.h | 1 +
 mm/shmem.c                             | 6 +++---
 mm/truncate.c                          | 2 +-
 6 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6b7dfb5e6871..18656b5f329b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3716,10 +3716,10 @@ struct vm_unmapped_area_info {
 extern unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info);
 
 /* truncate.c */
-extern void truncate_inode_pages(struct address_space *, loff_t);
-extern void truncate_inode_pages_range(struct address_space *,
-				       loff_t lstart, loff_t lend);
-extern void truncate_inode_pages_final(struct address_space *);
+void truncate_inode_pages(struct address_space *mapping, loff_t lstart);
+void truncate_inode_pages_range(struct address_space *mapping, loff_t lstart,
+		uoff_t lend);
+void truncate_inode_pages_final(struct address_space *mapping);
 
 /* generic vm_area_ops exported for stackable file systems */
 extern vm_fault_t filemap_fault(struct vm_fault *vmf);
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 2f3c36d92c03..f6aa916f4d1e 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -126,7 +126,7 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 					pgoff_t index, gfp_t gfp_mask);
 int shmem_writeout(struct folio *folio, struct swap_iocb **plug,
 		struct list_head *folio_list);
-void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end);
+void shmem_truncate_range(struct inode *inode, loff_t start, uoff_t end);
 int shmem_unuse(unsigned int type);
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
diff --git a/include/linux/types.h b/include/linux/types.h
index 6dfdb8e8e4c3..d4437e9c452c 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -50,6 +50,7 @@ typedef __kernel_old_gid_t	old_gid_t;
 
 #if defined(__GNUC__)
 typedef __kernel_loff_t		loff_t;
+typedef __kernel_uoff_t		uoff_t;
 #endif
 
 /*
diff --git a/include/uapi/asm-generic/posix_types.h b/include/uapi/asm-generic/posix_types.h
index b5f7594eee7a..0a90ad92dbf3 100644
--- a/include/uapi/asm-generic/posix_types.h
+++ b/include/uapi/asm-generic/posix_types.h
@@ -86,6 +86,7 @@ typedef struct {
  */
 typedef __kernel_long_t	__kernel_off_t;
 typedef long long	__kernel_loff_t;
+typedef unsigned long long	__kernel_uoff_t;
 typedef __kernel_long_t	__kernel_old_time_t;
 #ifndef __KERNEL__
 typedef __kernel_long_t	__kernel_time_t;
diff --git a/mm/shmem.c b/mm/shmem.c
index 7950f2a3f6d7..c33e9471ec78 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1093,7 +1093,7 @@ static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
  * Remove range of pages and swap entries from page cache, and free them.
  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
  */
-static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
+static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,
 								 bool unfalloc)
 {
 	struct address_space *mapping = inode->i_mapping;
@@ -1244,7 +1244,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 	shmem_recalc_inode(inode, 0, -nr_swaps_freed);
 }
 
-void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+void shmem_truncate_range(struct inode *inode, loff_t lstart, uoff_t lend)
 {
 	shmem_undo_range(inode, lstart, lend, false);
 	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
@@ -5784,7 +5784,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
 }
 #endif
 
-void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+void shmem_truncate_range(struct inode *inode, loff_t lstart, uoff_t lend)
 {
 	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
 }
diff --git a/mm/truncate.c b/mm/truncate.c
index d08340afc768..12467c1bd711 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -364,7 +364,7 @@ long mapping_evict_folio(struct address_space *mapping, struct folio *folio)
  * page aligned properly.
  */
 void truncate_inode_pages_range(struct address_space *mapping,
-				loff_t lstart, loff_t lend)
+				loff_t lstart, uoff_t lend)
 {
 	pgoff_t		start;		/* inclusive */
 	pgoff_t		end;		/* exclusive */
-- 
2.47.2