1 files changed, 61 insertions, 25 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 1a3afd469e3a..875314ee6f59 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1313,7 +1313,7 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			return err;
 
 		if (fc->handle_killpriv_v2 &&
-		    should_remove_suid(file_dentry(file))) {
+		    setattr_should_drop_suidgid(&init_user_ns, file_inode(file))) {
 			goto writethrough;
 		}
 
@@ -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);
 	}
@@ -2963,11 +3000,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
 		.mode = mode
 	};
 	int err;
-	bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) ||
-			   (mode & (FALLOC_FL_PUNCH_HOLE |
-				    FALLOC_FL_ZERO_RANGE));
-
-	bool block_faults = FUSE_IS_DAX(inode) && lock_inode;
+	bool block_faults = FUSE_IS_DAX(inode) &&
+		(!(mode & FALLOC_FL_KEEP_SIZE) ||
+		 (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)));
 
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
 		     FALLOC_FL_ZERO_RANGE))
@@ -2976,22 +3011,20 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
 	if (fm->fc->no_fallocate)
 		return -EOPNOTSUPP;
 
-	if (lock_inode) {
-		inode_lock(inode);
-		if (block_faults) {
-			filemap_invalidate_lock(inode->i_mapping);
-			err = fuse_dax_break_layouts(inode, 0, 0);
-			if (err)
-				goto out;
-		}
+	inode_lock(inode);
+	if (block_faults) {
+		filemap_invalidate_lock(inode->i_mapping);
+		err = fuse_dax_break_layouts(inode, 0, 0);
+		if (err)
+			goto out;
+	}
 
-		if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) {
-			loff_t endbyte = offset + length - 1;
+	if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) {
+		loff_t endbyte = offset + length - 1;
 
-			err = fuse_writeback_range(inode, offset, endbyte);
-			if (err)
-				goto out;
-		}
+		err = fuse_writeback_range(inode, offset, endbyte);
+		if (err)
+			goto out;
 	}
 
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
@@ -3001,6 +3034,10 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
 			goto out;
 	}
 
+	err = file_modified(file);
+	if (err)
+		goto out;
+
 	if (!(mode & FALLOC_FL_KEEP_SIZE))
 		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
 
@@ -3035,8 +3072,7 @@ out:
 	if (block_faults)
 		filemap_invalidate_unlock(inode->i_mapping);
 
-	if (lock_inode)
-		inode_unlock(inode);
+	inode_unlock(inode);
 
 	fuse_flush_time_update(inode);