fuse: fix wrong ff->iomode state changes from parallel dio write

There is a confusion with fuse_file_uncached_io_{start,end} interface.
These helpers do two things when called from passthrough open()/release():
1. Take/drop negative refcount of fi->iocachectr (inode uncached io mode)
2. State change ff->iomode IOM_NONE <-> IOM_UNCACHED (file uncached open)

The calls from parallel dio write path need to take a reference on
fi->iocachectr, but they should not be changing ff->iomode state, because
in this case, the fi->iocachectr reference does not stick around until file
release().

Factor out helpers fuse_inode_uncached_io_{start,end}, to be used from
parallel dio write path and rename fuse_file_*cached_io_{start,end} helpers
to fuse_file_*cached_io_{open,release} to clarify the difference.

Fixes: 205c1d802683 ("fuse: allow parallel dio writes with FUSE_DIRECT_IO_ALLOW_MMAP")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a56e7bffd000..b57ce4157640 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1362,7 +1362,7 @@ static void fuse_dio_lock(struct kiocb *iocb, struct iov_iter *from,
 			  bool *exclusive)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
-	struct fuse_file *ff = iocb->ki_filp->private_data;
+	struct fuse_inode *fi = get_fuse_inode(inode);
 
 	*exclusive = fuse_dio_wr_exclusive_lock(iocb, from);
 	if (*exclusive) {
@@ -1377,7 +1377,7 @@ static void fuse_dio_lock(struct kiocb *iocb, struct iov_iter *from,
 		 * have raced, so check it again.
 		 */
 		if (fuse_io_past_eof(iocb, from) ||
-		    fuse_file_uncached_io_start(inode, ff, NULL) != 0) {
+		    fuse_inode_uncached_io_start(fi, NULL) != 0) {
 			inode_unlock_shared(inode);
 			inode_lock(inode);
 			*exclusive = true;
@@ -1388,13 +1388,13 @@ static void fuse_dio_lock(struct kiocb *iocb, struct iov_iter *from,
 static void fuse_dio_unlock(struct kiocb *iocb, bool exclusive)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
-	struct fuse_file *ff = iocb->ki_filp->private_data;
+	struct fuse_inode *fi = get_fuse_inode(inode);
 
 	if (exclusive) {
 		inode_unlock(inode);
 	} else {
 		/* Allow opens in caching mode after last parallel dio end */
-		fuse_file_uncached_io_end(inode, ff);
+		fuse_inode_uncached_io_end(fi);
 		inode_unlock_shared(inode);
 	}
 }
@@ -2574,8 +2574,10 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
 		 * First mmap of direct_io file enters caching inode io mode.
 		 * Also waits for parallel dio writers to go into serial mode
 		 * (exclusive instead of shared lock).
+		 * After first mmap, the inode stays in caching io mode until
+		 * the direct_io file release.
 		 */
-		rc = fuse_file_cached_io_start(inode, ff);
+		rc = fuse_file_cached_io_open(inode, ff);
 		if (rc)
 			return rc;
 	}