Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

7 files changed, 807 insertions, 0 deletions

diff --git a/fs/qnx4/Kconfig b/fs/qnx4/Kconfig
new file mode 100644
index 000000000..a2eb826e7
--- /dev/null
+++ b/fs/qnx4/Kconfig
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config QNX4FS_FS
+	tristate "QNX4 file system support (read only)"
+	depends on BLOCK
+	select BUFFER_HEAD
+	help
+	  This is the file system used by the real-time operating systems
+	  QNX 4 and QNX 6 (the latter is also called QNX RTP).
+	  Further information is available at <http://www.qnx.com/>.
+	  Say Y if you intend to mount QNX hard disks or floppies.
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called qnx4.
+
+	  If you don't know whether you need it, then you don't need it:
+	  answer N.
diff --git a/fs/qnx4/Makefile b/fs/qnx4/Makefile
new file mode 100644
index 000000000..42d4fc263
--- /dev/null
+++ b/fs/qnx4/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the linux qnx4-filesystem routines.
+#
+
+obj-$(CONFIG_QNX4FS_FS) += qnx4.o
+
+qnx4-objs := inode.o dir.o namei.o bitmap.o
diff --git a/fs/qnx4/bitmap.c b/fs/qnx4/bitmap.c
new file mode 100644
index 000000000..163afc4ba
--- /dev/null
+++ b/fs/qnx4/bitmap.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * QNX4 file system, Linux implementation.
+ *
+ * Version : 0.2.1
+ *
+ * Using parts of the xiafs filesystem.
+ *
+ * History :
+ *
+ * 28-05-1998 by Richard Frowijn : first release.
+ * 20-06-1998 by Frank Denis : basic optimisations.
+ * 25-06-1998 by Frank Denis : qnx4_is_free, qnx4_set_bitmap, qnx4_bmap .
+ * 28-06-1998 by Frank Denis : qnx4_free_inode (to be fixed) .
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/bitops.h>
+#include "qnx4.h"
+
+unsigned long qnx4_count_free_blocks(struct super_block *sb)
+{
+	int start = le32_to_cpu(qnx4_sb(sb)->BitMap->di_first_xtnt.xtnt_blk) - 1;
+	int total = 0;
+	int total_free = 0;
+	int offset = 0;
+	int size = le32_to_cpu(qnx4_sb(sb)->BitMap->di_size);
+	struct buffer_head *bh;
+
+	while (total < size) {
+		int bytes = min(size - total, QNX4_BLOCK_SIZE);
+
+		if ((bh = sb_bread(sb, start + offset)) == NULL) {
+			printk(KERN_ERR "qnx4: I/O error in counting free blocks\n");
+			break;
+		}
+		total_free += bytes * BITS_PER_BYTE -
+				memweight(bh->b_data, bytes);
+		brelse(bh);
+		total += bytes;
+		offset++;
+	}
+
+	return total_free;
+}
diff --git a/fs/qnx4/dir.c b/fs/qnx4/dir.c
new file mode 100644
index 000000000..a9038d231
--- /dev/null
+++ b/fs/qnx4/dir.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * QNX4 file system, Linux implementation.
+ *
+ * Version : 0.2.1
+ *
+ * Using parts of the xiafs filesystem.
+ *
+ * History :
+ *
+ * 28-05-1998 by Richard Frowijn : first release.
+ * 20-06-1998 by Frank Denis : Linux 2.1.99+ & dcache support.
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/filelock.h>
+#include "qnx4.h"
+
+static int qnx4_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct inode *inode = file_inode(file);
+	unsigned int offset;
+	struct buffer_head *bh;
+	unsigned long blknum;
+	int ix, ino;
+	int size;
+
+	QNX4DEBUG((KERN_INFO "qnx4_readdir:i_size = %ld\n", (long) inode->i_size));
+	QNX4DEBUG((KERN_INFO "pos                 = %ld\n", (long) ctx->pos));
+
+	while (ctx->pos < inode->i_size) {
+		blknum = qnx4_block_map(inode, ctx->pos >> QNX4_BLOCK_SIZE_BITS);
+		bh = sb_bread(inode->i_sb, blknum);
+		if (bh == NULL) {
+			printk(KERN_ERR "qnx4_readdir: bread failed (%ld)\n", blknum);
+			return 0;
+		}
+		ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK;
+		for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) {
+			union qnx4_directory_entry *de;
+			const char *fname;
+
+			offset = ix * QNX4_DIR_ENTRY_SIZE;
+			de = (union qnx4_directory_entry *) (bh->b_data + offset);
+
+			fname = get_entry_fname(de, &size);
+			if (!fname)
+				continue;
+
+			if (!(de->de_status & QNX4_FILE_LINK)) {
+				ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1;
+			} else {
+				ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) *
+					QNX4_INODES_PER_BLOCK +
+					de->link.dl_inode_ndx;
+			}
+
+			QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, fname));
+			if (!dir_emit(ctx, fname, size, ino, DT_UNKNOWN)) {
+				brelse(bh);
+				return 0;
+			}
+		}
+		brelse(bh);
+	}
+	return 0;
+}
+
+const struct file_operations qnx4_dir_operations =
+{
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= qnx4_readdir,
+	.fsync		= simple_fsync,
+	.setlease	= generic_setlease,
+};
+
+const struct inode_operations qnx4_dir_inode_operations =
+{
+	.lookup		= qnx4_lookup,
+};
diff --git a/fs/qnx4/inode.c b/fs/qnx4/inode.c
new file mode 100644
index 000000000..42fcd500f
--- /dev/null
+++ b/fs/qnx4/inode.c
@@ -0,0 +1,436 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * QNX4 file system, Linux implementation.
+ *
+ * Version : 0.2.1
+ *
+ * Using parts of the xiafs filesystem.
+ *
+ * History :
+ *
+ * 01-06-1998 by Richard Frowijn : first release.
+ * 20-06-1998 by Frank Denis : Linux 2.1.99+ support, boot signature, misc.
+ * 30-06-1998 by Frank Denis : first step to write inodes.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/highuid.h>
+#include <linux/pagemap.h>
+#include <linux/buffer_head.h>
+#include <linux/writeback.h>
+#include <linux/statfs.h>
+#include <linux/fs_context.h>
+#include "qnx4.h"
+
+#define QNX4_VERSION  4
+#define QNX4_BMNAME   ".bitmap"
+
+static const struct super_operations qnx4_sops;
+
+static struct inode *qnx4_alloc_inode(struct super_block *sb);
+static void qnx4_free_inode(struct inode *inode);
+static int qnx4_statfs(struct dentry *, struct kstatfs *);
+static int qnx4_get_tree(struct fs_context *fc);
+
+static const struct super_operations qnx4_sops =
+{
+	.alloc_inode	= qnx4_alloc_inode,
+	.free_inode	= qnx4_free_inode,
+	.statfs		= qnx4_statfs,
+};
+
+static int qnx4_reconfigure(struct fs_context *fc)
+{
+	struct super_block *sb = fc->root->d_sb;
+	struct qnx4_sb_info *qs;
+
+	sync_filesystem(sb);
+	qs = qnx4_sb(sb);
+	qs->Version = QNX4_VERSION;
+	fc->sb_flags |= SB_RDONLY;
+	return 0;
+}
+
+static const struct fs_context_operations qnx4_context_opts = {
+	.get_tree	= qnx4_get_tree,
+	.reconfigure	= qnx4_reconfigure,
+};
+
+static int qnx4_get_block( struct inode *inode, sector_t iblock, struct buffer_head *bh, int create )
+{
+	unsigned long phys;
+
+	QNX4DEBUG((KERN_INFO "qnx4: qnx4_get_block inode=[%llu] iblock=[%ld]\n", inode->i_ino, iblock));
+
+	phys = qnx4_block_map( inode, iblock );
+	if ( phys ) {
+		// logical block is before EOF
+		map_bh(bh, inode->i_sb, phys);
+	}
+	return 0;
+}
+
+static inline u32 try_extent(qnx4_xtnt_t *extent, u32 *offset)
+{
+	u32 size = le32_to_cpu(extent->xtnt_size);
+	if (*offset < size)
+		return le32_to_cpu(extent->xtnt_blk) + *offset - 1;
+	*offset -= size;
+	return 0;
+}
+
+unsigned long qnx4_block_map( struct inode *inode, long iblock )
+{
+	int ix;
+	long i_xblk;
+	struct buffer_head *bh = NULL;
+	struct qnx4_xblk *xblk = NULL;
+	struct qnx4_inode_entry *qnx4_inode = qnx4_raw_inode(inode);
+	u16 nxtnt = le16_to_cpu(qnx4_inode->di_num_xtnts);
+	u32 offset = iblock;
+	u32 block = try_extent(&qnx4_inode->di_first_xtnt, &offset);
+
+	if (block) {
+		// iblock is in the first extent. This is easy.
+	} else {
+		// iblock is beyond first extent. We have to follow the extent chain.
+		i_xblk = le32_to_cpu(qnx4_inode->di_xblk);
+		ix = 0;
+		while ( --nxtnt > 0 ) {
+			if ( ix == 0 ) {
+				// read next xtnt block.
+				bh = sb_bread(inode->i_sb, i_xblk - 1);
+				if ( !bh ) {
+					QNX4DEBUG((KERN_ERR "qnx4: I/O error reading xtnt block [%ld])\n", i_xblk - 1));
+					return -EIO;
+				}
+				xblk = (struct qnx4_xblk*)bh->b_data;
+				if ( memcmp( xblk->xblk_signature, "IamXblk", 7 ) ) {
+					QNX4DEBUG((KERN_ERR "qnx4: block at %ld is not a valid xtnt\n", qnx4_inode->i_xblk));
+					return -EIO;
+				}
+			}
+			block = try_extent(&xblk->xblk_xtnts[ix], &offset);
+			if (block) {
+				// got it!
+				break;
+			}
+			if ( ++ix >= xblk->xblk_num_xtnts ) {
+				i_xblk = le32_to_cpu(xblk->xblk_next_xblk);
+				ix = 0;
+				brelse( bh );
+				bh = NULL;
+			}
+		}
+		if ( bh )
+			brelse( bh );
+	}
+
+	QNX4DEBUG((KERN_INFO "qnx4: mapping block %ld of inode %llu = %ld\n", iblock, inode->i_ino, block));
+	return block;
+}
+
+static int qnx4_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct super_block *sb = dentry->d_sb;
+	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
+
+	buf->f_type    = sb->s_magic;
+	buf->f_bsize   = sb->s_blocksize;
+	buf->f_blocks  = le32_to_cpu(qnx4_sb(sb)->BitMap->di_size) * 8;
+	buf->f_bfree   = qnx4_count_free_blocks(sb);
+	buf->f_bavail  = buf->f_bfree;
+	buf->f_namelen = QNX4_NAME_MAX;
+	buf->f_fsid    = u64_to_fsid(id);
+
+	return 0;
+}
+
+/*
+ * Check the root directory of the filesystem to make sure
+ * it really _is_ a qnx4 filesystem, and to check the size
+ * of the directory entry.
+ */
+static const char *qnx4_checkroot(struct super_block *sb,
+				  struct qnx4_super_block *s)
+{
+	struct buffer_head *bh;
+	struct qnx4_inode_entry *rootdir;
+	int rd, rl;
+	int i, j;
+
+	if (s->RootDir.di_fname[0] != '/' || s->RootDir.di_fname[1] != '\0')
+		return "no qnx4 filesystem (no root dir).";
+	QNX4DEBUG((KERN_NOTICE "QNX4 filesystem found on dev %s.\n", sb->s_id));
+	rd = le32_to_cpu(s->RootDir.di_first_xtnt.xtnt_blk) - 1;
+	rl = le32_to_cpu(s->RootDir.di_first_xtnt.xtnt_size);
+	for (j = 0; j < rl; j++) {
+		bh = sb_bread(sb, rd + j);	/* root dir, first block */
+		if (bh == NULL)
+			return "unable to read root entry.";
+		rootdir = (struct qnx4_inode_entry *) bh->b_data;
+		for (i = 0; i < QNX4_INODES_PER_BLOCK; i++, rootdir++) {
+			QNX4DEBUG((KERN_INFO "rootdir entry found : [%s]\n", rootdir->di_fname));
+			if (strcmp(rootdir->di_fname, QNX4_BMNAME) != 0)
+				continue;
+			qnx4_sb(sb)->BitMap = kmemdup(rootdir,
+						      sizeof(struct qnx4_inode_entry),
+						      GFP_KERNEL);
+			brelse(bh);
+			if (!qnx4_sb(sb)->BitMap)
+				return "not enough memory for bitmap inode";
+			/* keep bitmap inode known */
+			return NULL;
+		}
+		brelse(bh);
+	}
+	return "bitmap file not found.";
+}
+
+static int qnx4_fill_super(struct super_block *s, struct fs_context *fc)
+{
+	struct buffer_head *bh;
+	struct inode *root;
+	const char *errmsg;
+	struct qnx4_sb_info *qs;
+	int silent = fc->sb_flags & SB_SILENT;
+
+	qs = kzalloc_obj(struct qnx4_sb_info);
+	if (!qs)
+		return -ENOMEM;
+	s->s_fs_info = qs;
+
+	if (!sb_set_blocksize(s, QNX4_BLOCK_SIZE))
+		return -EINVAL;
+
+	s->s_op = &qnx4_sops;
+	s->s_magic = QNX4_SUPER_MAGIC;
+	s->s_flags |= SB_RDONLY;	/* Yup, read-only yet */
+	s->s_time_min = 0;
+	s->s_time_max = U32_MAX;
+
+	/* Check the superblock signature. Since the qnx4 code is
+	   dangerous, we should leave as quickly as possible
+	   if we don't belong here... */
+	bh = sb_bread(s, 1);
+	if (!bh) {
+		printk(KERN_ERR "qnx4: unable to read the superblock\n");
+		return -EINVAL;
+	}
+
+ 	/* check before allocating dentries, inodes, .. */
+	errmsg = qnx4_checkroot(s, (struct qnx4_super_block *) bh->b_data);
+	brelse(bh);
+	if (errmsg != NULL) {
+		if (!silent)
+			printk(KERN_ERR "qnx4: %s\n", errmsg);
+		return -EINVAL;
+	}
+
+ 	/* does root not have inode number QNX4_ROOT_INO ?? */
+	root = qnx4_iget(s, QNX4_ROOT_INO * QNX4_INODES_PER_BLOCK);
+	if (IS_ERR(root)) {
+		printk(KERN_ERR "qnx4: get inode failed\n");
+		return PTR_ERR(root);
+ 	}
+
+ 	s->s_root = d_make_root(root);
+ 	if (s->s_root == NULL)
+ 		return -ENOMEM;
+
+	return 0;
+}
+
+static int qnx4_get_tree(struct fs_context *fc)
+{
+	return get_tree_bdev(fc, qnx4_fill_super);
+}
+
+static int qnx4_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &qnx4_context_opts;
+
+	return 0;
+}
+
+static void qnx4_kill_sb(struct super_block *sb)
+{
+	struct qnx4_sb_info *qs = qnx4_sb(sb);
+	kill_block_super(sb);
+	if (qs) {
+		kfree(qs->BitMap);
+		kfree(qs);
+	}
+}
+
+static int qnx4_read_folio(struct file *file, struct folio *folio)
+{
+	return block_read_full_folio(folio, qnx4_get_block);
+}
+
+static sector_t qnx4_bmap(struct address_space *mapping, sector_t block)
+{
+	return generic_block_bmap(mapping,block,qnx4_get_block);
+}
+
+static const struct address_space_operations qnx4_aops = {
+	.read_folio	= qnx4_read_folio,
+	.bmap		= qnx4_bmap
+};
+
+struct inode *qnx4_iget(struct super_block *sb, unsigned long ino)
+{
+	struct buffer_head *bh;
+	struct qnx4_inode_entry *raw_inode;
+	int block;
+	struct qnx4_inode_entry *qnx4_inode;
+	struct inode *inode;
+
+	inode = iget_locked(sb, ino);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+	if (!(inode_state_read_once(inode) & I_NEW))
+		return inode;
+
+	qnx4_inode = qnx4_raw_inode(inode);
+	inode->i_mode = 0;
+
+	QNX4DEBUG((KERN_INFO "reading inode : [%d]\n", ino));
+	if (!ino) {
+		printk(KERN_ERR "qnx4: bad inode number on dev %s: %lu is "
+				"out of range\n",
+		       sb->s_id, ino);
+		iget_failed(inode);
+		return ERR_PTR(-EIO);
+	}
+	block = ino / QNX4_INODES_PER_BLOCK;
+
+	if (!(bh = sb_bread(sb, block))) {
+		printk(KERN_ERR "qnx4: major problem: unable to read inode from dev "
+		       "%s\n", sb->s_id);
+		iget_failed(inode);
+		return ERR_PTR(-EIO);
+	}
+	raw_inode = ((struct qnx4_inode_entry *) bh->b_data) +
+	    (ino % QNX4_INODES_PER_BLOCK);
+
+	inode->i_mode    = le16_to_cpu(raw_inode->di_mode);
+	i_uid_write(inode, (uid_t)le16_to_cpu(raw_inode->di_uid));
+	i_gid_write(inode, (gid_t)le16_to_cpu(raw_inode->di_gid));
+	set_nlink(inode, le16_to_cpu(raw_inode->di_nlink));
+	inode->i_size    = le32_to_cpu(raw_inode->di_size);
+	inode_set_mtime(inode, le32_to_cpu(raw_inode->di_mtime), 0);
+	inode_set_atime(inode, le32_to_cpu(raw_inode->di_atime), 0);
+	inode_set_ctime(inode, le32_to_cpu(raw_inode->di_ctime), 0);
+	inode->i_blocks  = le32_to_cpu(raw_inode->di_first_xtnt.xtnt_size);
+
+	memcpy(qnx4_inode, raw_inode, QNX4_DIR_ENTRY_SIZE);
+	if (S_ISREG(inode->i_mode)) {
+		inode->i_fop = &generic_ro_fops;
+		inode->i_mapping->a_ops = &qnx4_aops;
+		qnx4_i(inode)->mmu_private = inode->i_size;
+	} else if (S_ISDIR(inode->i_mode)) {
+		inode->i_op = &qnx4_dir_inode_operations;
+		inode->i_fop = &qnx4_dir_operations;
+	} else if (S_ISLNK(inode->i_mode)) {
+		inode->i_op = &page_symlink_inode_operations;
+		inode_nohighmem(inode);
+		inode->i_mapping->a_ops = &qnx4_aops;
+		qnx4_i(inode)->mmu_private = inode->i_size;
+	} else {
+		printk(KERN_ERR "qnx4: bad inode %lu on dev %s\n",
+			ino, sb->s_id);
+		iget_failed(inode);
+		brelse(bh);
+		return ERR_PTR(-EIO);
+	}
+	brelse(bh);
+	unlock_new_inode(inode);
+	return inode;
+}
+
+static struct kmem_cache *qnx4_inode_cachep;
+
+static struct inode *qnx4_alloc_inode(struct super_block *sb)
+{
+	struct qnx4_inode_info *ei;
+	ei = alloc_inode_sb(sb, qnx4_inode_cachep, GFP_KERNEL);
+	if (!ei)
+		return NULL;
+	return &ei->vfs_inode;
+}
+
+static void qnx4_free_inode(struct inode *inode)
+{
+	kmem_cache_free(qnx4_inode_cachep, qnx4_i(inode));
+}
+
+static void init_once(void *foo)
+{
+	struct qnx4_inode_info *ei = (struct qnx4_inode_info *) foo;
+
+	inode_init_once(&ei->vfs_inode);
+}
+
+static int init_inodecache(void)
+{
+	qnx4_inode_cachep = kmem_cache_create("qnx4_inode_cache",
+					     sizeof(struct qnx4_inode_info),
+					     0, (SLAB_RECLAIM_ACCOUNT|
+						SLAB_ACCOUNT),
+					     init_once);
+	if (qnx4_inode_cachep == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+static void destroy_inodecache(void)
+{
+	/*
+	 * Make sure all delayed rcu free inodes are flushed before we
+	 * destroy cache.
+	 */
+	rcu_barrier();
+	kmem_cache_destroy(qnx4_inode_cachep);
+}
+
+static struct file_system_type qnx4_fs_type = {
+	.owner			= THIS_MODULE,
+	.name			= "qnx4",
+	.kill_sb		= qnx4_kill_sb,
+	.fs_flags		= FS_REQUIRES_DEV,
+	.init_fs_context	= qnx4_init_fs_context,
+};
+MODULE_ALIAS_FS("qnx4");
+
+static int __init init_qnx4_fs(void)
+{
+	int err;
+
+	err = init_inodecache();
+	if (err)
+		return err;
+
+	err = register_filesystem(&qnx4_fs_type);
+	if (err) {
+		destroy_inodecache();
+		return err;
+	}
+
+	printk(KERN_INFO "QNX4 filesystem 0.2.3 registered.\n");
+	return 0;
+}
+
+static void __exit exit_qnx4_fs(void)
+{
+	unregister_filesystem(&qnx4_fs_type);
+	destroy_inodecache();
+}
+
+module_init(init_qnx4_fs)
+module_exit(exit_qnx4_fs)
+MODULE_DESCRIPTION("QNX4 file system");
+MODULE_LICENSE("GPL");
+
diff --git a/fs/qnx4/namei.c b/fs/qnx4/namei.c
new file mode 100644
index 000000000..bb8db6550
--- /dev/null
+++ b/fs/qnx4/namei.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0
+/* 
+ * QNX4 file system, Linux implementation.
+ * 
+ * Version : 0.2.1
+ * 
+ * Using parts of the xiafs filesystem.
+ * 
+ * History :
+ * 
+ * 01-06-1998 by Richard Frowijn : first release.
+ * 21-06-1998 by Frank Denis : dcache support, fixed error codes.
+ * 04-07-1998 by Frank Denis : first step for rmdir/unlink.
+ */
+
+#include <linux/buffer_head.h>
+#include "qnx4.h"
+
+
+/*
+ * check if the filename is correct. For some obscure reason, qnx writes a
+ * new file twice in the directory entry, first with all possible options at 0
+ * and for a second time the way it is, they want us not to access the qnx
+ * filesystem when whe are using linux.
+ */
+static int qnx4_match(int len, const char *name,
+		      struct buffer_head *bh, unsigned long *offset)
+{
+	union qnx4_directory_entry *de;
+	const char *fname;
+	int fnamelen;
+
+	if (bh == NULL) {
+		printk(KERN_WARNING "qnx4: matching unassigned buffer !\n");
+		return 0;
+	}
+	de = (union qnx4_directory_entry *) (bh->b_data + *offset);
+	*offset += QNX4_DIR_ENTRY_SIZE;
+
+	fname = get_entry_fname(de, &fnamelen);
+	if (!fname || len != fnamelen)
+		return 0;
+
+	if (strncmp(name, fname, len) == 0)
+		return 1;
+
+	return 0;
+}
+
+static struct buffer_head *qnx4_find_entry(int len, struct inode *dir,
+	   const char *name, struct qnx4_inode_entry **res_dir, int *ino)
+{
+	unsigned long block, offset, blkofs;
+	struct buffer_head *bh;
+
+	*res_dir = NULL;
+	bh = NULL;
+	block = offset = blkofs = 0;
+	while (blkofs * QNX4_BLOCK_SIZE + offset < dir->i_size) {
+		if (!bh) {
+			block = qnx4_block_map(dir, blkofs);
+			if (block)
+				bh = sb_bread(dir->i_sb, block);
+			if (!bh) {
+				blkofs++;
+				continue;
+			}
+		}
+		*res_dir = (struct qnx4_inode_entry *) (bh->b_data + offset);
+		if (qnx4_match(len, name, bh, &offset)) {
+			*ino = block * QNX4_INODES_PER_BLOCK +
+			    (offset / QNX4_DIR_ENTRY_SIZE) - 1;
+			return bh;
+		}
+		if (offset < bh->b_size) {
+			continue;
+		}
+		brelse(bh);
+		bh = NULL;
+		offset = 0;
+		blkofs++;
+	}
+	brelse(bh);
+	*res_dir = NULL;
+	return NULL;
+}
+
+struct dentry * qnx4_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	int ino;
+	struct qnx4_inode_entry *de;
+	struct qnx4_link_info *lnk;
+	struct buffer_head *bh;
+	const char *name = dentry->d_name.name;
+	int len = dentry->d_name.len;
+	struct inode *foundinode = NULL;
+
+	if (!(bh = qnx4_find_entry(len, dir, name, &de, &ino)))
+		goto out;
+	/* The entry is linked, let's get the real info */
+	if ((de->di_status & QNX4_FILE_LINK) == QNX4_FILE_LINK) {
+		lnk = (struct qnx4_link_info *) de;
+		ino = (le32_to_cpu(lnk->dl_inode_blk) - 1) *
+                    QNX4_INODES_PER_BLOCK +
+		    lnk->dl_inode_ndx;
+	}
+	brelse(bh);
+
+	foundinode = qnx4_iget(dir->i_sb, ino);
+	if (IS_ERR(foundinode))
+		QNX4DEBUG((KERN_ERR "qnx4: lookup->iget -> error %ld\n",
+			   PTR_ERR(foundinode)));
+out:
+	return d_splice_alias(foundinode, dentry);
+}
diff --git a/fs/qnx4/qnx4.h b/fs/qnx4/qnx4.h
new file mode 100644
index 000000000..5c2b1fb6b
--- /dev/null
+++ b/fs/qnx4/qnx4.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/fs.h>
+#include <linux/qnx4_fs.h>
+
+#define QNX4_DEBUG 0
+
+#if QNX4_DEBUG
+#define QNX4DEBUG(X) printk X
+#else
+#define QNX4DEBUG(X) (void) 0
+#endif
+
+struct qnx4_sb_info {
+	unsigned int		Version;	/* may be useful */
+	struct qnx4_inode_entry	*BitMap;	/* useful */
+};
+
+struct qnx4_inode_info {
+	struct qnx4_inode_entry raw;
+	loff_t mmu_private;
+	struct inode vfs_inode;
+};
+
+extern struct inode *qnx4_iget(struct super_block *, unsigned long);
+extern struct dentry *qnx4_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags);
+extern unsigned long qnx4_count_free_blocks(struct super_block *sb);
+extern unsigned long qnx4_block_map(struct inode *inode, long iblock);
+
+extern const struct inode_operations qnx4_dir_inode_operations;
+extern const struct file_operations qnx4_dir_operations;
+extern int qnx4_is_free(struct super_block *sb, long block);
+
+static inline struct qnx4_sb_info *qnx4_sb(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+static inline struct qnx4_inode_info *qnx4_i(struct inode *inode)
+{
+	return container_of(inode, struct qnx4_inode_info, vfs_inode);
+}
+
+static inline struct qnx4_inode_entry *qnx4_raw_inode(struct inode *inode)
+{
+	return &qnx4_i(inode)->raw;
+}
+
+/*
+ * A qnx4 directory entry is an inode entry or link info
+ * depending on the status field in the last byte. The
+ * first byte is where the name start either way, and a
+ * zero means it's empty.
+ *
+ * Also, due to a bug in gcc, we don't want to use the
+ * real (differently sized) name arrays in the inode and
+ * link entries, but always the 'de_name[]' one in the
+ * fake struct entry.
+ *
+ * See
+ *
+ *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
+ *
+ * for details, but basically gcc will take the size of the
+ * 'name' array from one of the used union entries randomly.
+ *
+ * This use of 'de_name[]' (48 bytes) avoids the false positive
+ * warnings that would happen if gcc decides to use 'inode.di_name'
+ * (16 bytes) even when the pointer and size were to come from
+ * 'link.dl_name' (48 bytes).
+ *
+ * In all cases the actual name pointer itself is the same, it's
+ * only the gcc internal 'what is the size of this field' logic
+ * that can get confused.
+ */
+union qnx4_directory_entry {
+	struct {
+		const char de_name[48];
+		u8 de_pad[15];
+		u8 de_status;
+	};
+	struct qnx4_inode_entry inode;
+	struct qnx4_link_info link;
+};
+
+static inline const char *get_entry_fname(union qnx4_directory_entry *de,
+					  int *size)
+{
+	/* Make sure the status byte is in the same place for all structs. */
+	BUILD_BUG_ON(offsetof(struct qnx4_inode_entry, di_status) !=
+			offsetof(struct qnx4_link_info, dl_status));
+	BUILD_BUG_ON(offsetof(struct qnx4_inode_entry, di_status) !=
+			offsetof(union qnx4_directory_entry, de_status));
+
+	if (!de->de_name[0])
+		return NULL;
+	if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
+		return NULL;
+	if (!(de->de_status & QNX4_FILE_LINK))
+		*size = sizeof(de->inode.di_fname);
+	else
+		*size = sizeof(de->link.dl_fname);
+
+	*size = strnlen(de->de_name, *size);
+
+	return de->de_name;
+}