On 26/05/24 09:02AM, Dave Chinner wrote:

On Mon, May 20, 2024 at 03:50:18PM +0530, Nitesh Shetty wrote:

quoted

From: Anuj Gupta <redacted>

This is a prep patch. Allow copy_file_range to work for block devices.
Relaxing generic_copy_file_checks allows us to reuse the existing infra,
instead of adding a new user interface for block copy offload.
Change generic_copy_file_checks to use ->f_mapping->host for both inode_in
and inode_out. Allow block device in generic_file_rw_checks.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Anuj Gupta <redacted>
Signed-off-by: Nitesh Shetty <redacted>
---
 fs/read_write.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index ef6339391351..31645ca5ed58 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c

@@ -1413,8 +1413,8 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
 				    struct file *file_out, loff_t pos_out,
 				    size_t *req_count, unsigned int flags)
 {
-	struct inode *inode_in = file_inode(file_in);
-	struct inode *inode_out = file_inode(file_out);
+	struct inode *inode_in = file_in->f_mapping->host;
+	struct inode *inode_out = file_out->f_mapping->host;
 	uint64_t count = *req_count;
 	loff_t size_in;
 	int ret;

Ok, so this changes from file->f_inode to file->mapping->host. No
doubt this is because of how bdev inode mappings are munged.
However, the first code that is run here is:

ret = generic_file_rw_checks(file_in, file_out);

and that function still uses file_inode().

Hence there checks:

quoted

@@ -1726,7 +1726,9 @@ int generic_file_rw_checks(struct file *file_in, struct file *file_out)
 	/* Don't copy dirs, pipes, sockets... */
 	if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
 		return -EISDIR;
-	if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
+	if (!S_ISREG(inode_in->i_mode) && !S_ISBLK(inode_in->i_mode))
+		return -EINVAL;
+	if ((inode_in->i_mode & S_IFMT) != (inode_out->i_mode & S_IFMT))
 		return -EINVAL;

.... are being done on different inodes to the rest of
generic_copy_file_checks() when block devices are used.

Is this correct? If so, this needs a pair of comments (one for each
function) to explain why the specific inode used for these functions
is correct for block devices....

We were getting wrong size with file_inode() for block device, but we
missed to do it here in generic_file_rw_checks.
We will change the generic_file_rw_checks to use file->mapping->host
to make it consistent.

Thank You,
Nitesh Shetty