Merge tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse update from Miklos Szeredi:

 - Allow some write requests to proceed in parallel

 - Fix a performance problem with allow_sys_admin_access

 - Add a special kind of invalidation that doesn't immediately purge
   submounts

 - On revalidation treat the target of rename(RENAME_NOREPLACE) the same
   as open(O_EXCL)

 - Use type safe helpers for some mnt_userns transformations

* tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: Rearrange fuse_allow_current_process checks
  fuse: allow non-extending parallel direct writes on the same file
  fuse: remove the unneeded result variable
  fuse: port to vfs{g,u}id_t and associated helpers
  fuse: Remove user_ns check for FUSE_DEV_IOC_CLONE
  fuse: always revalidate rename target dentry
  fuse: add "expire only" mode to FUSE_NOTIFY_INVAL_ENTRY
  fs/fuse: Replace kmap() with kmap_local_page()

1 files changed, 40 insertions, 3 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index c996c0ef8c63..875314ee6f59 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1563,14 +1563,47 @@ static ssize_t fuse_direct_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	return res;
 }
 
+static bool fuse_direct_write_extending_i_size(struct kiocb *iocb,
+					       struct iov_iter *iter)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	return iocb->ki_pos + iov_iter_count(iter) > i_size_read(inode);
+}
+
 static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
 	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
 	ssize_t res;
+	bool exclusive_lock =
+		!(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES) ||
+		iocb->ki_flags & IOCB_APPEND ||
+		fuse_direct_write_extending_i_size(iocb, from);
+
+	/*
+	 * Take exclusive lock if
+	 * - Parallel direct writes are disabled - a user space decision
+	 * - Parallel direct writes are enabled and i_size is being extended.
+	 *   This might not be needed at all, but needs further investigation.
+	 */
+	if (exclusive_lock)
+		inode_lock(inode);
+	else {
+		inode_lock_shared(inode);
+
+		/* A race with truncate might have come up as the decision for
+		 * the lock type was done without holding the lock, check again.
+		 */
+		if (fuse_direct_write_extending_i_size(iocb, from)) {
+			inode_unlock_shared(inode);
+			inode_lock(inode);
+			exclusive_lock = true;
+		}
+	}
 
-	/* Don't allow parallel writes to the same file */
-	inode_lock(inode);
 	res = generic_write_checks(iocb, from);
 	if (res > 0) {
 		if (!is_sync_kiocb(iocb) && iocb->ki_flags & IOCB_DIRECT) {
@@ -1581,7 +1614,10 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			fuse_write_update_attr(inode, iocb->ki_pos, res);
 		}
 	}
-	inode_unlock(inode);
+	if (exclusive_lock)
+		inode_unlock(inode);
+	else
+		inode_unlock_shared(inode);
 
 	return res;
 }
@@ -2931,6 +2967,7 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 
 	if (iov_iter_rw(iter) == WRITE) {
 		fuse_write_update_attr(inode, pos, ret);
+		/* For extending writes we already hold exclusive lock */
 		if (ret < 0 && offset + count > i_size)
 			fuse_do_truncate(file);
 	}