[f2fs-dev] [RFC PATCH 05/10] fsverity: Add call back to decide if verity check has to be performed

[Chandan Rajendra]

Ext4 and F2FS store verity metadata in data extents (beyond
inode->i_size) associated with a file. But other filesystems might
choose alternative means to store verity metadata. Hence this commit
adds a callback function pointer to 'struct fsverity_operations' to help
in deciding if verity operation needs to performed against a page-cache
page holding file data.

Signed-off-by: Chandan Rajendra <chan...@linux.ibm.com>
---
 fs/ext4/super.c          | 9 +++++++++
 fs/post_read_process.c   | 5 +++--
 include/linux/fsverity.h | 1 +
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9314dddfbf34..2d7781ab6824 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1428,10 +1428,19 @@ static struct page 
*ext4_read_verity_metadata_page(struct inode *inode,
        return read_mapping_page(inode->i_mapping, index, NULL);
 }
 
+static bool ext4_verity_required(struct inode *inode, pgoff_t index)
+{
+       if (index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT))
+               return true;
+       else
+               return false;
+}
+
 static const struct fsverity_operations ext4_verityops = {
        .set_verity             = ext4_set_verity,
        .get_metadata_end       = ext4_get_verity_metadata_end,
        .read_metadata_page     = ext4_read_verity_metadata_page,
+       .verity_required        = ext4_verity_required,
 };
 #endif /* CONFIG_FS_VERITY */
 
diff --git a/fs/post_read_process.c b/fs/post_read_process.c
index 9720eeff0160..1f8663d70247 100644
--- a/fs/post_read_process.c
+++ b/fs/post_read_process.c
@@ -79,8 +79,9 @@ struct bio_post_read_ctx *get_bio_post_read_ctx(struct inode 
*inode,
        if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
                post_read_steps |= 1 << STEP_DECRYPT;
 #ifdef CONFIG_FS_VERITY
-       if (inode->i_verity_info != NULL &&
-               (index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
+       if (inode->i_verity_info != NULL
+               && inode->i_sb->s_vop->verity_required
+               && inode->i_sb->s_vop->verity_required(inode, index))
                post_read_steps |= 1 << STEP_VERITY;
 #endif
        if (post_read_steps) {
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index 7c33b42abf1b..b83712d6c79a 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -18,6 +18,7 @@ struct fsverity_operations {
        int (*set_verity)(struct inode *inode, loff_t data_i_size);
        int (*get_metadata_end)(struct inode *inode, loff_t *metadata_end_ret);
        struct page *(*read_metadata_page)(struct inode *inode, pgoff_t index);
+       bool (*verity_required)(struct inode *inode, pgoff_t index);
 };
 
 #ifdef CONFIG_FS_VERITY
-- 
2.19.1



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