Implement splice-read for overlayfs by passing the request down a layer
rather than going through generic_file_splice_read() which is going to be
changed to assume that ->read_folio() is present on buffered files.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Christoph Hellwig <hch@xxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
cc: John Hubbard <jhubbard@xxxxxxxxxx>
cc: David Hildenbrand <david@xxxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: Miklos Szeredi <miklos@xxxxxxxxxx>
cc: linux-unionfs@xxxxxxxxxxxxxxx
cc: linux-block@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
---
Notes:
ver #17)
- Use vfs_splice_read() helper rather than open-coding checks.
ver #15)
- Remove redundant FMODE_CAN_ODIRECT check on real file.
- Do rw_verify_area() on the real file, not the overlay file.
- Fix a file leak.
fs/overlayfs/file.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 7c04f033aadd..86197882ff35 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -419,6 +419,27 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
return ret;
}
+static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len,
+ unsigned int flags)
+{
+ const struct cred *old_cred;
+ struct fd real;
+ ssize_t ret;
+
+ ret = ovl_real_fdget(in, &real);
+ if (ret)
+ return ret;
+
+ old_cred = ovl_override_creds(file_inode(in)->i_sb);
+ ret = vfs_splice_read(real.file, ppos, pipe, len, flags);
+ revert_creds(old_cred);
+ ovl_file_accessed(in);
+
+ fdput(real);
+ return ret;
+}
+
/*
* Calling iter_file_splice_write() directly from overlay's f_op may deadlock
* due to lock order inversion between pipe->mutex in iter_file_splice_write()
@@ -695,7 +716,7 @@ const struct file_operations ovl_file_operations = {
.fallocate = ovl_fallocate,
.fadvise = ovl_fadvise,
.flush = ovl_flush,
- .splice_read = generic_file_splice_read,
+ .splice_read = ovl_splice_read,
.splice_write = ovl_splice_write,
.copy_file_range = ovl_copy_file_range,
