[PATCH v21 22/30] ocfs2: Provide a splice-read stub

David Howells
2023-05-20T00:02:19Z

Provide a splice_read stub for ocfs2. This emits trace lines and does an
atime lock/update before calling filemap_splice_read(). Splicing from
direct I/O is handled by the caller.

A couple of new tracepoints are added for this purpose.

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: Mark Fasheh <mark@fasheh.com>
cc: Joel Becker <jlbec@evilplan.org>
cc: Joseph Qi <joseph.qi@linux.alibaba.com>
cc: ocfs2-devel@oss.oracle.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-mm@kvack.org
---
fs/ocfs2/file.c | 39 ++++++++++++++++++++++++++++++++++++++-
fs/ocfs2/ocfs2_trace.h | 3 +++
2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index efb09de4343d..f7e00b5689d5 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2581,6 +2581,43 @@ static ssize_t ocfs2_file_read_iter(struct kiocb *iocb,
return ret;
}

+static ssize_t ocfs2_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);
+ ssize_t ret = 0;
+ int lock_level = 0;
+
+ trace_ocfs2_file_splice_read(inode, in, in->f_path.dentry,
+ (unsigned long long)OCFS2_I(inode)->ip_blkno,
+ in->f_path.dentry->d_name.len,
+ in->f_path.dentry->d_name.name,
+ 0);
+
+ /*
+ * We're fine letting folks race truncates and extending writes with
+ * read across the cluster, just like they can locally. Hence no
+ * rw_lock during read.
+ *
+ * Take and drop the meta data lock to update inode fields like i_size.
+ * This allows the checks down below generic_file_splice_read() a
+ * chance of actually working.
+ */
+ ret = ocfs2_inode_lock_atime(inode, in->f_path.mnt, &lock_level, true);
+ if (ret < 0) {
+ if (ret != -EAGAIN)
+ mlog_errno(ret);
+ goto bail;
+ }
+ ocfs2_inode_unlock(inode, lock_level);
+
+ ret = filemap_splice_read(in, ppos, pipe, len, flags);
+ trace_filemap_splice_read_ret(ret);
+bail:
+ return ret;
+}
+
/* Refer generic_file_llseek_unlocked() */
static loff_t ocfs2_file_llseek(struct file *file, loff_t offset, int whence)
{
@@ -2744,7 +2781,7 @@ const struct file_operations ocfs2_fops = {
#endif
.lock = ocfs2_lock,
.flock = ocfs2_flock,
- .splice_read = generic_file_splice_read,
+ .splice_read = ocfs2_file_splice_read,
.splice_write = iter_file_splice_write,
.fallocate = ocfs2_fallocate,
.remap_file_range = ocfs2_remap_file_range,
diff --git a/fs/ocfs2/ocfs2_trace.h b/fs/ocfs2/ocfs2_trace.h
index dc4bce1649c1..b8c3d1702076 100644
--- a/fs/ocfs2/ocfs2_trace.h
+++ b/fs/ocfs2/ocfs2_trace.h
@@ -1319,6 +1319,8 @@ DEFINE_OCFS2_FILE_OPS(ocfs2_file_splice_write);

DEFINE_OCFS2_FILE_OPS(ocfs2_file_read_iter);

+DEFINE_OCFS2_FILE_OPS(ocfs2_file_splice_read);
+
DEFINE_OCFS2_ULL_ULL_ULL_EVENT(ocfs2_truncate_file);

DEFINE_OCFS2_ULL_ULL_EVENT(ocfs2_truncate_file_error);
@@ -1470,6 +1472,7 @@ TRACE_EVENT(ocfs2_prepare_inode_for_write,
);

DEFINE_OCFS2_INT_EVENT(generic_file_read_iter_ret);
+DEFINE_OCFS2_INT_EVENT(filemap_splice_read_ret);

/* End of trace events for fs/ocfs2/file.c. */