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Subject[patch 4/6] ocfs2: fix i_mutex locking in ocfs2_splice_to_file()
Rearrange locking of i_mutex on destination and call to
ocfs2_rw_lock() so locks are only held while buffers are copied with
the pipe_to_file() actor, and not while waiting for more data on the
pipe.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/ocfs2/file.c | 96 ++++++++++++++++++++++++++++++++++++++-----------
fs/splice.c | 5 +-
include/linux/splice.h | 2 +
3 files changed, 80 insertions(+), 23 deletions(-)

Index: linux-2.6/fs/ocfs2/file.c
===================================================================
--- linux-2.6.orig/fs/ocfs2/file.c 2009-04-14 16:35:15.000000000 +0200
+++ linux-2.6/fs/ocfs2/file.c 2009-04-14 18:29:58.000000000 +0200
@@ -1912,6 +1912,22 @@ out_sems:
return written ? written : ret;
}

+static int ocfs2_splice_to_file(struct pipe_inode_info *pipe,
+ struct file *out,
+ struct splice_desc *sd)
+{
+ int ret;
+
+ ret = ocfs2_prepare_inode_for_write(out->f_path.dentry, &sd->pos,
+ sd->total_len, 0, NULL);
+ if (ret < 0) {
+ mlog_errno(ret);
+ return ret;
+ }
+
+ return splice_from_pipe_feed(pipe, sd, pipe_to_file);
+}
+
static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
struct file *out,
loff_t *ppos,
@@ -1919,38 +1935,76 @@ static ssize_t ocfs2_file_splice_write(s
unsigned int flags)
{
int ret;
- struct inode *inode = out->f_path.dentry->d_inode;
+ struct address_space *mapping = out->f_mapping;
+ struct inode *inode = mapping->host;
+ struct splice_desc sd = {
+ .total_len = len,
+ .flags = flags,
+ .pos = *ppos,
+ .u.file = out,
+ };

mlog_entry("(0x%p, 0x%p, %u, '%.*s')\n", out, pipe,
(unsigned int)len,
out->f_path.dentry->d_name.len,
out->f_path.dentry->d_name.name);

- mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
-
- ret = ocfs2_rw_lock(inode, 1);
- if (ret < 0) {
- mlog_errno(ret);
- goto out;
- }
+ if (pipe->inode)
+ mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_PARENT);

- ret = ocfs2_prepare_inode_for_write(out->f_path.dentry, ppos, len, 0,
- NULL);
- if (ret < 0) {
- mlog_errno(ret);
- goto out_unlock;
- }
+ splice_from_pipe_begin(&sd);
+ do {
+ ret = splice_from_pipe_next(pipe, &sd);
+ if (ret <= 0)
+ break;
+
+ mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
+ ret = ocfs2_rw_lock(inode, 1);
+ if (ret < 0)
+ mlog_errno(ret);
+ else {
+ ret = ocfs2_splice_to_file(pipe, out, &sd);
+ ocfs2_rw_unlock(inode, 1);
+ }
+ mutex_unlock(&inode->i_mutex);
+ } while (ret > 0);
+ splice_from_pipe_end(pipe, &sd);

if (pipe->inode)
- mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_CHILD);
- ret = generic_file_splice_write_nolock(pipe, out, ppos, len, flags);
- if (pipe->inode)
mutex_unlock(&pipe->inode->i_mutex);

-out_unlock:
- ocfs2_rw_unlock(inode, 1);
-out:
- mutex_unlock(&inode->i_mutex);
+ if (sd.num_spliced)
+ ret = sd.num_spliced;
+
+ if (ret > 0) {
+ unsigned long nr_pages;
+
+ *ppos += ret;
+ nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+
+ /*
+ * If file or inode is SYNC and we actually wrote some data,
+ * sync it.
+ */
+ if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
+ int err;
+
+ mutex_lock(&inode->i_mutex);
+ err = ocfs2_rw_lock(inode, 1);
+ if (err < 0) {
+ mlog_errno(err);
+ } else {
+ err = generic_osync_inode(inode, mapping,
+ OSYNC_METADATA|OSYNC_DATA);
+ ocfs2_rw_unlock(inode, 1);
+ }
+ mutex_unlock(&inode->i_mutex);
+
+ if (err)
+ ret = err;
+ }
+ balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
+ }

mlog_exit(ret);
return ret;
Index: linux-2.6/fs/splice.c
===================================================================
--- linux-2.6.orig/fs/splice.c 2009-04-14 18:25:13.000000000 +0200
+++ linux-2.6/fs/splice.c 2009-04-14 18:29:58.000000000 +0200
@@ -555,8 +555,8 @@ static int pipe_to_sendpage(struct pipe_
* SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
* a new page in the output file page cache and fill/dirty that.
*/
-static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
- struct splice_desc *sd)
+int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
+ struct splice_desc *sd)
{
struct file *file = sd->u.file;
struct address_space *mapping = file->f_mapping;
@@ -600,6 +600,7 @@ static int pipe_to_file(struct pipe_inod
out:
return ret;
}
+EXPORT_SYMBOL(pipe_to_file);

static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
{
Index: linux-2.6/include/linux/splice.h
===================================================================
--- linux-2.6.orig/include/linux/splice.h 2009-04-14 17:37:47.000000000 +0200
+++ linux-2.6/include/linux/splice.h 2009-04-14 18:29:58.000000000 +0200
@@ -75,6 +75,8 @@ extern int splice_from_pipe_next(struct
extern void splice_from_pipe_begin(struct splice_desc *);
extern void splice_from_pipe_end(struct pipe_inode_info *,
struct splice_desc *);
+extern int pipe_to_file(struct pipe_inode_info *, struct pipe_buffer *,
+ struct splice_desc *);

extern ssize_t splice_to_pipe(struct pipe_inode_info *,
struct splice_pipe_desc *);
--


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