[PATCH v7 06/22] fsverity: hoist pagecache_read from f2fs/ext4 to fsverity

Andrey Albershteyn
2026-04-09T13:14:29Z

This is the same function to read from pageache. XFS will also need
this, so move this to core fsverity.

Note that f2fs and ext4 functions diverged a bit, as ext4 operated over
folios and f2fs operated over pages. The common one will operate over
folios.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
---
fs/ext4/verity.c | 32 +++-----------------------------
fs/f2fs/verity.c | 30 +-----------------------------
fs/verity/pagecache.c | 33 +++++++++++++++++++++++++++++++++
include/linux/fsverity.h | 2 ++
4 files changed, 39 insertions(+), 58 deletions(-)

diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
index 347945ac23a4..ac5c133f5529 100644
--- a/fs/ext4/verity.c
+++ b/fs/ext4/verity.c
@@ -34,32 +34,6 @@ static inline loff_t ext4_verity_metadata_pos(const struct inode *inode)
return round_up(inode->i_size, 65536);
}

-/*
- * Read some verity metadata from the inode. __vfs_read() can't be used because
- * we need to read beyond i_size.
- */
-static int pagecache_read(struct inode *inode, void *buf, size_t count,
- loff_t pos)
-{
- while (count) {
- struct folio *folio;
- size_t n;
-
- folio = read_mapping_folio(inode->i_mapping, pos >> PAGE_SHIFT,
- NULL);
- if (IS_ERR(folio))
- return PTR_ERR(folio);
-
- n = memcpy_from_file_folio(buf, folio, pos, count);
- folio_put(folio);
-
- buf += n;
- pos += n;
- count -= n;
- }
- return 0;
-}
-
/*
* Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
* kernel_write() can't be used because the file descriptor is readonly.
@@ -311,8 +285,8 @@ static int ext4_get_verity_descriptor_location(struct inode *inode,
goto bad;
desc_size_pos -= sizeof(desc_size_disk);

- err = pagecache_read(inode, &desc_size_disk, sizeof(desc_size_disk),
- desc_size_pos);
+ err = fsverity_pagecache_read(inode, &desc_size_disk,
+ sizeof(desc_size_disk), desc_size_pos);
if (err)
return err;
desc_size = le32_to_cpu(desc_size_disk);
@@ -352,7 +326,7 @@ static int ext4_get_verity_descriptor(struct inode *inode, void *buf,
if (buf_size) {
if (desc_size > buf_size)
return -ERANGE;
- err = pagecache_read(inode, buf, desc_size, desc_pos);
+ err = fsverity_pagecache_read(inode, buf, desc_size, desc_pos);
if (err)
return err;
}
diff --git a/fs/f2fs/verity.c b/fs/f2fs/verity.c
index b3b3e71604ac..5ea0a9b40443 100644
--- a/fs/f2fs/verity.c
+++ b/fs/f2fs/verity.c
@@ -36,34 +36,6 @@ static inline loff_t f2fs_verity_metadata_pos(const struct inode *inode)
return round_up(inode->i_size, 65536);
}

-/*
- * Read some verity metadata from the inode. __vfs_read() can't be used because
- * we need to read beyond i_size.
- */
-static int pagecache_read(struct inode *inode, void *buf, size_t count,
- loff_t pos)
-{
- while (count) {
- size_t n = min_t(size_t, count,
- PAGE_SIZE - offset_in_page(pos));
- struct page *page;
-
- page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
- NULL);
- if (IS_ERR(page))
- return PTR_ERR(page);
-
- memcpy_from_page(buf, page, offset_in_page(pos), n);
-
- put_page(page);
-
- buf += n;
- pos += n;
- count -= n;
- }
- return 0;
-}
-
/*
* Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
* kernel_write() can't be used because the file descriptor is readonly.
@@ -248,7 +220,7 @@ static int f2fs_get_verity_descriptor(struct inode *inode, void *buf,
if (buf_size) {
if (size > buf_size)
return -ERANGE;
- res = pagecache_read(inode, buf, size, pos);
+ res = fsverity_pagecache_read(inode, buf, size, pos);
if (res)
return res;
}
diff --git a/fs/verity/pagecache.c b/fs/verity/pagecache.c
index 99f5f53eea98..9d82e6b74ba1 100644
--- a/fs/verity/pagecache.c
+++ b/fs/verity/pagecache.c
@@ -78,3 +78,36 @@ void fsverity_fill_zerohash(struct folio *folio, size_t offset, size_t len,
vi->tree_params.digest_size);
}
EXPORT_SYMBOL_GPL(fsverity_fill_zerohash);
+
+/**
+ * fsverity_pagecache_read() - read page and copy data to buffer
+ * @inode: copy from this inode's address space
+ * @buf: buffer to copy to
+ * @count: number of bytes to copy
+ * @pos: position of the folio to copy from
+ *
+ * Read some verity metadata from the inode. __vfs_read() can't be used because
+ * we need to read beyond i_size.
+ */
+int fsverity_pagecache_read(struct inode *inode, void *buf, size_t count,
+ loff_t pos)
+{
+ while (count) {
+ struct folio *folio;
+ size_t n;
+
+ folio = read_mapping_folio(inode->i_mapping, pos >> PAGE_SHIFT,
+ NULL);
+ if (IS_ERR(folio))
+ return PTR_ERR(folio);
+
+ n = memcpy_from_file_folio(buf, folio, pos, count);
+ folio_put(folio);
+
+ buf += n;
+ pos += n;
+ count -= n;
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(fsverity_pagecache_read);
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index a5645ec07aa8..a2ae5cc649ad 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -328,5 +328,7 @@ void fsverity_cleanup_inode(struct inode *inode);
struct page *generic_read_merkle_tree_page(struct inode *inode, pgoff_t index);
void generic_readahead_merkle_tree(struct inode *inode, pgoff_t index,
unsigned long nr_pages);
+int fsverity_pagecache_read(struct inode *inode, void *buf, size_t count,
+ loff_t pos);

#endif /* _LINUX_FSVERITY_H */
--
2.51.2