[PATCH v21 25/30] zonefs: Provide a splice-read stub

David Howells
2023-05-20T00:02:21Z

Provide a splice_read stub for zonefs. This does some checks before
proceeding and locks the inode across the call to filemap_splice_read() and
a size check in case of truncation. Splicing from direct I/O is handled by
the caller.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Darrick J. Wong <djwong@kernel.org>
cc: linux-xfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-mm@kvack.org
---
fs/zonefs/file.c | 40 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/fs/zonefs/file.c b/fs/zonefs/file.c
index 132f01d3461f..65d4c4fe6364 100644
--- a/fs/zonefs/file.c
+++ b/fs/zonefs/file.c
@@ -752,6 +752,44 @@ static ssize_t zonefs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
return ret;
}

+static ssize_t zonefs_file_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe,
+ size_t len, unsigned int flags)
+{
+ struct inode *inode = file_inode(in);
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ struct zonefs_zone *z = zonefs_inode_zone(inode);
+ loff_t isize;
+ ssize_t ret = 0;
+
+ /* Offline zones cannot be read */
+ if (unlikely(IS_IMMUTABLE(inode) && !(inode->i_mode & 0777)))
+ return -EPERM;
+
+ if (*ppos >= z->z_capacity)
+ return 0;
+
+ inode_lock_shared(inode);
+
+ /* Limit read operations to written data */
+ mutex_lock(&zi->i_truncate_mutex);
+ isize = i_size_read(inode);
+ if (*ppos >= isize)
+ len = 0;
+ else
+ len = min_t(loff_t, len, isize - *ppos);
+ mutex_unlock(&zi->i_truncate_mutex);
+
+ if (len > 0) {
+ ret = filemap_splice_read(in, ppos, pipe, len, flags);
+ if (ret == -EIO)
+ zonefs_io_error(inode, false);
+ }
+
+ inode_unlock_shared(inode);
+ return ret;
+}
+
/*
* Write open accounting is done only for sequential files.
*/
@@ -896,7 +934,7 @@ const struct file_operations zonefs_file_operations = {
.llseek = zonefs_file_llseek,
.read_iter = zonefs_file_read_iter,
.write_iter = zonefs_file_write_iter,
- .splice_read = generic_file_splice_read,
+ .splice_read = zonefs_file_splice_read,
.splice_write = iter_file_splice_write,
.iopoll = iocb_bio_iopoll,
};