David Howells
2023-May-22 13:50 UTC
[Ocfs2-devel] [PATCH v22 22/31] ocfs2: Provide a splice-read wrapper
Provide a splice_read wrapper 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 at redhat.com>
Reviewed-by: Joseph Qi <joseph.qi at linux.alibaba.com>
cc: Christoph Hellwig <hch at lst.de>
cc: Al Viro <viro at zeniv.linux.org.uk>
cc: Jens Axboe <axboe at kernel.dk>
cc: Mark Fasheh <mark at fasheh.com>
cc: Joel Becker <jlbec at evilplan.org>
cc: ocfs2-devel at oss.oracle.com
cc: linux-fsdevel at vger.kernel.org
cc: linux-block at vger.kernel.org
cc: linux-mm at kvack.org
---
Notes:
ver #22:
- Adjust a couple of comments mentioning generic_file_splice_read().
- Pass 1 to ocfs2_inode_lock_atomic() rather than true.
- Pass the splice flags into the tracepoint.
fs/ocfs2/file.c | 41 +++++++++++++++++++++++++++++++++++++++--
fs/ocfs2/ocfs2_trace.h | 3 +++
2 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index efb09de4343d..86add13b5f23 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2552,7 +2552,7 @@ static ssize_t ocfs2_file_read_iter(struct kiocb *iocb,
*
* Take and drop the meta data lock to update inode fields
* like i_size. This allows the checks down below
- * generic_file_read_iter() a chance of actually working.
+ * copy_splice_read() a chance of actually working.
*/
ret = ocfs2_inode_lock_atime(inode, filp->f_path.mnt, &lock_level,
!nowait);
@@ -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,
+ flags);
+
+ /*
+ * 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 filemap_splice_read() a chance of
+ * actually working.
+ */
+ ret = ocfs2_inode_lock_atime(inode, in->f_path.mnt, &lock_level, 1);
+ 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. */