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

1 files changed, 792 insertions, 0 deletions

diff --git a/fs/ext4/fsmap.c b/fs/ext4/fsmap.c
new file mode 100644
index 000000000..8b1138d2d
--- /dev/null
+++ b/fs/ext4/fsmap.c
@@ -0,0 +1,792 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#include "ext4.h"
+#include <linux/fsmap.h>
+#include "fsmap.h"
+#include "mballoc.h"
+#include <linux/sort.h>
+#include <linux/list_sort.h>
+#include <trace/events/ext4.h>
+
+/* Convert an ext4_fsmap to an fsmap. */
+void ext4_fsmap_from_internal(struct super_block *sb, struct fsmap *dest,
+			      struct ext4_fsmap *src)
+{
+	dest->fmr_device = src->fmr_device;
+	dest->fmr_flags = src->fmr_flags;
+	dest->fmr_physical = src->fmr_physical << sb->s_blocksize_bits;
+	dest->fmr_owner = src->fmr_owner;
+	dest->fmr_offset = 0;
+	dest->fmr_length = src->fmr_length << sb->s_blocksize_bits;
+	dest->fmr_reserved[0] = 0;
+	dest->fmr_reserved[1] = 0;
+	dest->fmr_reserved[2] = 0;
+}
+
+/* Convert an fsmap to an ext4_fsmap. */
+void ext4_fsmap_to_internal(struct super_block *sb, struct ext4_fsmap *dest,
+			    struct fsmap *src)
+{
+	dest->fmr_device = src->fmr_device;
+	dest->fmr_flags = src->fmr_flags;
+	dest->fmr_physical = src->fmr_physical >> sb->s_blocksize_bits;
+	dest->fmr_owner = src->fmr_owner;
+	dest->fmr_length = src->fmr_length >> sb->s_blocksize_bits;
+}
+
+/* getfsmap query state */
+struct ext4_getfsmap_info {
+	struct ext4_fsmap_head	*gfi_head;
+	ext4_fsmap_format_t	gfi_formatter;	/* formatting fn */
+	void			*gfi_format_arg;/* format buffer */
+	ext4_fsblk_t		gfi_next_fsblk;	/* next fsblock we expect */
+	u32			gfi_dev;	/* device id */
+	ext4_group_t		gfi_agno;	/* bg number, if applicable */
+	struct ext4_fsmap	gfi_low;	/* low rmap key */
+	struct ext4_fsmap	gfi_high;	/* high rmap key */
+	struct ext4_fsmap	gfi_lastfree;	/* free ext at end of last bg */
+	struct list_head	gfi_meta_list;	/* fixed metadata list */
+	bool			gfi_last;	/* last extent? */
+};
+
+/* Associate a device with a getfsmap handler. */
+struct ext4_getfsmap_dev {
+	int			(*gfd_fn)(struct super_block *sb,
+				      struct ext4_fsmap *keys,
+				      struct ext4_getfsmap_info *info);
+	u32			gfd_dev;
+};
+
+/* Compare two getfsmap device handlers. */
+static int ext4_getfsmap_dev_compare(const void *p1, const void *p2)
+{
+	const struct ext4_getfsmap_dev *d1 = p1;
+	const struct ext4_getfsmap_dev *d2 = p2;
+
+	return d1->gfd_dev - d2->gfd_dev;
+}
+
+/* Compare a record against our starting point */
+static bool ext4_getfsmap_rec_before_low_key(struct ext4_getfsmap_info *info,
+					     struct ext4_fsmap *rec)
+{
+	return rec->fmr_physical + rec->fmr_length <=
+	       info->gfi_low.fmr_physical;
+}
+
+/*
+ * Format a reverse mapping for getfsmap, having translated rm_startblock
+ * into the appropriate daddr units.
+ */
+static int ext4_getfsmap_helper(struct super_block *sb,
+				struct ext4_getfsmap_info *info,
+				struct ext4_fsmap *rec)
+{
+	struct ext4_fsmap fmr;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	ext4_fsblk_t rec_fsblk = rec->fmr_physical;
+	ext4_group_t agno;
+	ext4_grpblk_t cno;
+	int error;
+
+	if (fatal_signal_pending(current))
+		return -EINTR;
+
+	/*
+	 * Filter out records that start before our startpoint, if the
+	 * caller requested that.
+	 */
+	if (ext4_getfsmap_rec_before_low_key(info, rec)) {
+		rec_fsblk += rec->fmr_length;
+		if (info->gfi_next_fsblk < rec_fsblk)
+			info->gfi_next_fsblk = rec_fsblk;
+		return EXT4_QUERY_RANGE_CONTINUE;
+	}
+
+	/* Are we just counting mappings? */
+	if (info->gfi_head->fmh_count == 0) {
+		if (info->gfi_head->fmh_entries == UINT_MAX)
+			return EXT4_QUERY_RANGE_ABORT;
+
+		if (rec_fsblk > info->gfi_next_fsblk)
+			info->gfi_head->fmh_entries++;
+
+		if (info->gfi_last)
+			return EXT4_QUERY_RANGE_CONTINUE;
+
+		info->gfi_head->fmh_entries++;
+
+		rec_fsblk += rec->fmr_length;
+		if (info->gfi_next_fsblk < rec_fsblk)
+			info->gfi_next_fsblk = rec_fsblk;
+		return EXT4_QUERY_RANGE_CONTINUE;
+	}
+
+	/*
+	 * If the record starts past the last physical block we saw,
+	 * then we've found a gap.  Report the gap as being owned by
+	 * whatever the caller specified is the missing owner.
+	 */
+	if (rec_fsblk > info->gfi_next_fsblk) {
+		if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
+			return EXT4_QUERY_RANGE_ABORT;
+
+		ext4_get_group_no_and_offset(sb, info->gfi_next_fsblk,
+				&agno, &cno);
+		trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno,
+				EXT4_C2B(sbi, cno),
+				rec_fsblk - info->gfi_next_fsblk,
+				EXT4_FMR_OWN_UNKNOWN);
+
+		fmr.fmr_device = info->gfi_dev;
+		fmr.fmr_physical = info->gfi_next_fsblk;
+		fmr.fmr_owner = EXT4_FMR_OWN_UNKNOWN;
+		fmr.fmr_length = rec_fsblk - info->gfi_next_fsblk;
+		fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
+		error = info->gfi_formatter(&fmr, info->gfi_format_arg);
+		if (error)
+			return error;
+		info->gfi_head->fmh_entries++;
+	}
+
+	if (info->gfi_last)
+		goto out;
+
+	/* Fill out the extent we found */
+	if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
+		return EXT4_QUERY_RANGE_ABORT;
+
+	ext4_get_group_no_and_offset(sb, rec_fsblk, &agno, &cno);
+	trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno, EXT4_C2B(sbi, cno),
+			rec->fmr_length, rec->fmr_owner);
+
+	fmr.fmr_device = info->gfi_dev;
+	fmr.fmr_physical = rec_fsblk;
+	fmr.fmr_owner = rec->fmr_owner;
+	fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
+	fmr.fmr_length = rec->fmr_length;
+	error = info->gfi_formatter(&fmr, info->gfi_format_arg);
+	if (error)
+		return error;
+	info->gfi_head->fmh_entries++;
+
+out:
+	rec_fsblk += rec->fmr_length;
+	if (info->gfi_next_fsblk < rec_fsblk)
+		info->gfi_next_fsblk = rec_fsblk;
+	return EXT4_QUERY_RANGE_CONTINUE;
+}
+
+static inline ext4_fsblk_t ext4_fsmap_next_pblk(struct ext4_fsmap *fmr)
+{
+	return fmr->fmr_physical + fmr->fmr_length;
+}
+
+static int ext4_getfsmap_meta_helper(struct super_block *sb,
+				     ext4_group_t agno, ext4_grpblk_t start,
+				     ext4_grpblk_t len, void *priv)
+{
+	struct ext4_getfsmap_info *info = priv;
+	struct ext4_fsmap *p;
+	struct ext4_fsmap *tmp;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	ext4_fsblk_t fsb, fs_start, fs_end;
+	int error;
+
+	fs_start = fsb = (EXT4_C2B(sbi, start) +
+			  ext4_group_first_block_no(sb, agno));
+	fs_end = fs_start + EXT4_C2B(sbi, len);
+
+	/*
+	 * Return relevant extents from the meta_list. We emit all extents that
+	 * partially/fully overlap with the query range
+	 */
+	list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
+		if (p->fmr_physical + p->fmr_length <= info->gfi_next_fsblk) {
+			list_del(&p->fmr_list);
+			kfree(p);
+			continue;
+		}
+		if (p->fmr_physical <= fs_end &&
+		    p->fmr_physical + p->fmr_length > fs_start) {
+			/* Emit the retained free extent record if present */
+			if (info->gfi_lastfree.fmr_owner) {
+				error = ext4_getfsmap_helper(sb, info,
+							&info->gfi_lastfree);
+				if (error)
+					return error;
+				info->gfi_lastfree.fmr_owner = 0;
+			}
+			error = ext4_getfsmap_helper(sb, info, p);
+			if (error)
+				return error;
+			fsb = p->fmr_physical + p->fmr_length;
+			if (info->gfi_next_fsblk < fsb)
+				info->gfi_next_fsblk = fsb;
+			list_del(&p->fmr_list);
+			kfree(p);
+			continue;
+		}
+	}
+	if (info->gfi_next_fsblk < fsb)
+		info->gfi_next_fsblk = fsb;
+
+	return 0;
+}
+
+
+/* Transform a blockgroup's free record into a fsmap */
+static int ext4_getfsmap_datadev_helper(struct super_block *sb,
+					ext4_group_t agno, ext4_grpblk_t start,
+					ext4_grpblk_t len, void *priv)
+{
+	struct ext4_fsmap irec;
+	struct ext4_getfsmap_info *info = priv;
+	struct ext4_fsmap *p;
+	struct ext4_fsmap *tmp;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	ext4_fsblk_t fsb;
+	ext4_fsblk_t fslen;
+	int error;
+
+	fsb = (EXT4_C2B(sbi, start) + ext4_group_first_block_no(sb, agno));
+	fslen = EXT4_C2B(sbi, len);
+
+	/* If the retained free extent record is set... */
+	if (info->gfi_lastfree.fmr_owner) {
+		/* ...and abuts this one, lengthen it and return. */
+		if (ext4_fsmap_next_pblk(&info->gfi_lastfree) == fsb) {
+			info->gfi_lastfree.fmr_length += fslen;
+			return 0;
+		}
+
+		/*
+		 * There's a gap between the two free extents; emit the
+		 * retained extent prior to merging the meta_list.
+		 */
+		error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
+		if (error)
+			return error;
+		info->gfi_lastfree.fmr_owner = 0;
+	}
+
+	/* Merge in any relevant extents from the meta_list */
+	list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
+		if (p->fmr_physical + p->fmr_length <= info->gfi_next_fsblk) {
+			list_del(&p->fmr_list);
+			kfree(p);
+		} else if (p->fmr_physical < fsb) {
+			error = ext4_getfsmap_helper(sb, info, p);
+			if (error)
+				return error;
+
+			list_del(&p->fmr_list);
+			kfree(p);
+		}
+	}
+
+	irec.fmr_device = 0;
+	irec.fmr_physical = fsb;
+	irec.fmr_length = fslen;
+	irec.fmr_owner = EXT4_FMR_OWN_FREE;
+	irec.fmr_flags = 0;
+
+	/* If this is a free extent at the end of a bg, buffer it. */
+	if (ext4_fsmap_next_pblk(&irec) ==
+			ext4_group_first_block_no(sb, agno + 1)) {
+		info->gfi_lastfree = irec;
+		return 0;
+	}
+
+	/* Otherwise, emit it */
+	return ext4_getfsmap_helper(sb, info, &irec);
+}
+
+/* Execute a getfsmap query against the log device. */
+static int ext4_getfsmap_logdev(struct super_block *sb, struct ext4_fsmap *keys,
+				struct ext4_getfsmap_info *info)
+{
+	journal_t *journal = EXT4_SB(sb)->s_journal;
+	struct ext4_fsmap irec;
+
+	/* Set up search keys */
+	info->gfi_low = keys[0];
+	info->gfi_low.fmr_length = 0;
+
+	memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
+
+	trace_ext4_fsmap_low_key(sb, info->gfi_dev, 0,
+			info->gfi_low.fmr_physical,
+			info->gfi_low.fmr_length,
+			info->gfi_low.fmr_owner);
+
+	trace_ext4_fsmap_high_key(sb, info->gfi_dev, 0,
+			info->gfi_high.fmr_physical,
+			info->gfi_high.fmr_length,
+			info->gfi_high.fmr_owner);
+
+	if (keys[0].fmr_physical > 0)
+		return 0;
+
+	/* Fabricate an rmap entry for the external log device. */
+	irec.fmr_physical = journal->j_blk_offset;
+	irec.fmr_length = journal->j_total_len;
+	irec.fmr_owner = EXT4_FMR_OWN_LOG;
+	irec.fmr_flags = 0;
+
+	return ext4_getfsmap_helper(sb, info, &irec);
+}
+
+/* Helper to fill out an ext4_fsmap. */
+static inline int ext4_getfsmap_fill(struct list_head *meta_list,
+				     ext4_fsblk_t fsb, ext4_fsblk_t len,
+				     uint64_t owner)
+{
+	struct ext4_fsmap *fsm;
+
+	fsm = kmalloc_obj(*fsm, GFP_NOFS);
+	if (!fsm)
+		return -ENOMEM;
+	fsm->fmr_device = 0;
+	fsm->fmr_flags = 0;
+	fsm->fmr_physical = fsb;
+	fsm->fmr_owner = owner;
+	fsm->fmr_length = len;
+	list_add_tail(&fsm->fmr_list, meta_list);
+
+	return 0;
+}
+
+/*
+ * This function returns the number of file system metadata blocks at
+ * the beginning of a block group, including the reserved gdt blocks.
+ */
+static unsigned int ext4_getfsmap_find_sb(struct super_block *sb,
+					  ext4_group_t agno,
+					  struct list_head *meta_list)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	ext4_fsblk_t fsb = ext4_group_first_block_no(sb, agno);
+	ext4_fsblk_t len;
+	unsigned long first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);
+	unsigned long metagroup = agno / EXT4_DESC_PER_BLOCK(sb);
+	int error;
+
+	/* Record the superblock. */
+	if (ext4_bg_has_super(sb, agno)) {
+		error = ext4_getfsmap_fill(meta_list, fsb, 1, EXT4_FMR_OWN_FS);
+		if (error)
+			return error;
+		fsb++;
+	}
+
+	/* Record the group descriptors. */
+	len = ext4_bg_num_gdb(sb, agno);
+	if (!len)
+		return 0;
+	error = ext4_getfsmap_fill(meta_list, fsb, len,
+				   EXT4_FMR_OWN_GDT);
+	if (error)
+		return error;
+	fsb += len;
+
+	/* Reserved GDT blocks */
+	if (!ext4_has_feature_meta_bg(sb) || metagroup < first_meta_bg) {
+		len = le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
+
+		/*
+		 * mkfs.ext4 can set s_reserved_gdt_blocks as 0 in some cases,
+		 * check for that.
+		 */
+		if (!len)
+			return 0;
+
+		error = ext4_getfsmap_fill(meta_list, fsb, len,
+					   EXT4_FMR_OWN_RESV_GDT);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+/* Compare two fsmap items. */
+static int ext4_getfsmap_compare(void *priv,
+				 const struct list_head *a,
+				 const struct list_head *b)
+{
+	struct ext4_fsmap *fa;
+	struct ext4_fsmap *fb;
+
+	fa = container_of(a, struct ext4_fsmap, fmr_list);
+	fb = container_of(b, struct ext4_fsmap, fmr_list);
+	if (fa->fmr_physical < fb->fmr_physical)
+		return -1;
+	else if (fa->fmr_physical > fb->fmr_physical)
+		return 1;
+	return 0;
+}
+
+/* Merge adjacent extents of fixed metadata. */
+static void ext4_getfsmap_merge_fixed_metadata(struct list_head *meta_list)
+{
+	struct ext4_fsmap *p;
+	struct ext4_fsmap *prev = NULL;
+	struct ext4_fsmap *tmp;
+
+	list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
+		if (!prev) {
+			prev = p;
+			continue;
+		}
+
+		if (prev->fmr_owner == p->fmr_owner &&
+		    prev->fmr_physical + prev->fmr_length == p->fmr_physical) {
+			prev->fmr_length += p->fmr_length;
+			list_del(&p->fmr_list);
+			kfree(p);
+		} else
+			prev = p;
+	}
+}
+
+/* Free a list of fixed metadata. */
+static void ext4_getfsmap_free_fixed_metadata(struct list_head *meta_list)
+{
+	struct ext4_fsmap *p;
+	struct ext4_fsmap *tmp;
+
+	list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
+		list_del(&p->fmr_list);
+		kfree(p);
+	}
+}
+
+/* Find all the fixed metadata in the filesystem. */
+static int ext4_getfsmap_find_fixed_metadata(struct super_block *sb,
+					     struct list_head *meta_list)
+{
+	struct ext4_group_desc *gdp;
+	ext4_group_t agno;
+	int error;
+
+	INIT_LIST_HEAD(meta_list);
+
+	/* Collect everything. */
+	for (agno = 0; agno < EXT4_SB(sb)->s_groups_count; agno++) {
+		gdp = ext4_get_group_desc(sb, agno, NULL);
+		if (!gdp) {
+			error = -EFSCORRUPTED;
+			goto err;
+		}
+
+		/* Superblock & GDT */
+		error = ext4_getfsmap_find_sb(sb, agno, meta_list);
+		if (error)
+			goto err;
+
+		/* Block bitmap */
+		error = ext4_getfsmap_fill(meta_list,
+					   ext4_block_bitmap(sb, gdp), 1,
+					   EXT4_FMR_OWN_BLKBM);
+		if (error)
+			goto err;
+
+		/* Inode bitmap */
+		error = ext4_getfsmap_fill(meta_list,
+					   ext4_inode_bitmap(sb, gdp), 1,
+					   EXT4_FMR_OWN_INOBM);
+		if (error)
+			goto err;
+
+		/* Inodes */
+		error = ext4_getfsmap_fill(meta_list,
+					   ext4_inode_table(sb, gdp),
+					   EXT4_SB(sb)->s_itb_per_group,
+					   EXT4_FMR_OWN_INODES);
+		if (error)
+			goto err;
+	}
+
+	/* Sort the list */
+	list_sort(NULL, meta_list, ext4_getfsmap_compare);
+
+	/* Merge adjacent extents */
+	ext4_getfsmap_merge_fixed_metadata(meta_list);
+
+	return 0;
+err:
+	ext4_getfsmap_free_fixed_metadata(meta_list);
+	return error;
+}
+
+/* Execute a getfsmap query against the buddy bitmaps */
+static int ext4_getfsmap_datadev(struct super_block *sb,
+				 struct ext4_fsmap *keys,
+				 struct ext4_getfsmap_info *info)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	ext4_fsblk_t start_fsb;
+	ext4_fsblk_t end_fsb;
+	ext4_fsblk_t bofs;
+	ext4_fsblk_t eofs;
+	ext4_group_t start_ag;
+	ext4_group_t end_ag;
+	ext4_grpblk_t first_cluster;
+	ext4_grpblk_t last_cluster;
+	struct ext4_fsmap irec;
+	int error = 0;
+
+	bofs = le32_to_cpu(sbi->s_es->s_first_data_block);
+	eofs = ext4_blocks_count(sbi->s_es);
+	if (keys[0].fmr_physical >= eofs)
+		return 0;
+	else if (keys[0].fmr_physical < bofs)
+		keys[0].fmr_physical = bofs;
+	if (keys[1].fmr_physical >= eofs)
+		keys[1].fmr_physical = eofs - 1;
+	if (keys[1].fmr_physical < keys[0].fmr_physical)
+		return 0;
+	start_fsb = keys[0].fmr_physical;
+	end_fsb = keys[1].fmr_physical;
+
+	/* Determine first and last group to examine based on start and end */
+	ext4_get_group_no_and_offset(sb, start_fsb, &start_ag, &first_cluster);
+	ext4_get_group_no_and_offset(sb, end_fsb, &end_ag, &last_cluster);
+
+	/*
+	 * Convert the fsmap low/high keys to bg based keys.  Initialize
+	 * low to the fsmap low key and max out the high key to the end
+	 * of the bg.
+	 */
+	info->gfi_low = keys[0];
+	info->gfi_low.fmr_physical = EXT4_C2B(sbi, first_cluster);
+	info->gfi_low.fmr_length = 0;
+
+	memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
+
+	/* Assemble a list of all the fixed-location metadata. */
+	error = ext4_getfsmap_find_fixed_metadata(sb, &info->gfi_meta_list);
+	if (error)
+		goto err;
+
+	/* Query each bg */
+	for (info->gfi_agno = start_ag;
+	     info->gfi_agno <= end_ag;
+	     info->gfi_agno++) {
+		/*
+		 * Set the bg high key from the fsmap high key if this
+		 * is the last bg that we're querying.
+		 */
+		if (info->gfi_agno == end_ag) {
+			info->gfi_high = keys[1];
+			info->gfi_high.fmr_physical = EXT4_C2B(sbi,
+					last_cluster);
+			info->gfi_high.fmr_length = 0;
+		}
+
+		trace_ext4_fsmap_low_key(sb, info->gfi_dev, info->gfi_agno,
+				info->gfi_low.fmr_physical,
+				info->gfi_low.fmr_length,
+				info->gfi_low.fmr_owner);
+
+		trace_ext4_fsmap_high_key(sb, info->gfi_dev, info->gfi_agno,
+				info->gfi_high.fmr_physical,
+				info->gfi_high.fmr_length,
+				info->gfi_high.fmr_owner);
+
+		error = ext4_mballoc_query_range(sb, info->gfi_agno,
+				EXT4_B2C(sbi, info->gfi_low.fmr_physical),
+				EXT4_B2C(sbi, info->gfi_high.fmr_physical),
+				ext4_getfsmap_meta_helper,
+				ext4_getfsmap_datadev_helper, info);
+		if (error)
+			goto err;
+
+		/*
+		 * Set the bg low key to the start of the bg prior to
+		 * moving on to the next bg.
+		 */
+		if (info->gfi_agno == start_ag)
+			memset(&info->gfi_low, 0, sizeof(info->gfi_low));
+	}
+
+	/* Do we have a retained free extent? */
+	if (info->gfi_lastfree.fmr_owner) {
+		error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
+		if (error)
+			goto err;
+	}
+
+	/*
+	 * The dummy record below will cause ext4_getfsmap_helper() to report
+	 * any allocated blocks at the end of the range.
+	 */
+	irec.fmr_device = 0;
+	irec.fmr_physical = end_fsb + 1;
+	irec.fmr_length = 0;
+	irec.fmr_owner = EXT4_FMR_OWN_FREE;
+	irec.fmr_flags = 0;
+
+	info->gfi_last = true;
+	error = ext4_getfsmap_helper(sb, info, &irec);
+	if (error)
+		goto err;
+
+err:
+	ext4_getfsmap_free_fixed_metadata(&info->gfi_meta_list);
+	return error;
+}
+
+/* Do we recognize the device? */
+static bool ext4_getfsmap_is_valid_device(struct super_block *sb,
+					  struct ext4_fsmap *fm)
+{
+	if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
+	    fm->fmr_device == new_encode_dev(sb->s_bdev->bd_dev))
+		return true;
+	if (EXT4_SB(sb)->s_journal_bdev_file &&
+	    fm->fmr_device ==
+	    new_encode_dev(file_bdev(EXT4_SB(sb)->s_journal_bdev_file)->bd_dev))
+		return true;
+	return false;
+}
+
+/* Ensure that the low key is less than the high key. */
+static bool ext4_getfsmap_check_keys(struct ext4_fsmap *low_key,
+				     struct ext4_fsmap *high_key)
+{
+	if (low_key->fmr_device > high_key->fmr_device)
+		return false;
+	if (low_key->fmr_device < high_key->fmr_device)
+		return true;
+
+	if (low_key->fmr_physical > high_key->fmr_physical)
+		return false;
+	if (low_key->fmr_physical < high_key->fmr_physical)
+		return true;
+
+	if (low_key->fmr_owner > high_key->fmr_owner)
+		return false;
+	if (low_key->fmr_owner < high_key->fmr_owner)
+		return true;
+
+	return false;
+}
+
+#define EXT4_GETFSMAP_DEVS	2
+/*
+ * Get filesystem's extents as described in head, and format for
+ * output.  Calls formatter to fill the user's buffer until all
+ * extents are mapped, until the passed-in head->fmh_count slots have
+ * been filled, or until the formatter short-circuits the loop, if it
+ * is tracking filled-in extents on its own.
+ *
+ * Key to Confusion
+ * ----------------
+ * There are multiple levels of keys and counters at work here:
+ * _fsmap_head.fmh_keys		-- low and high fsmap keys passed in;
+ * 				   these reflect fs-wide block addrs.
+ * dkeys			-- fmh_keys used to query each device;
+ * 				   these are fmh_keys but w/ the low key
+ * 				   bumped up by fmr_length.
+ * _getfsmap_info.gfi_next_fsblk-- next fs block we expect to see; this
+ *				   is how we detect gaps in the fsmap
+ *				   records and report them.
+ * _getfsmap_info.gfi_low/high	-- per-bg low/high keys computed from
+ * 				   dkeys; used to query the free space.
+ */
+int ext4_getfsmap(struct super_block *sb, struct ext4_fsmap_head *head,
+		  ext4_fsmap_format_t formatter, void *arg)
+{
+	struct ext4_fsmap dkeys[2];	/* per-dev keys */
+	struct ext4_getfsmap_dev handlers[EXT4_GETFSMAP_DEVS];
+	struct ext4_getfsmap_info info = { NULL };
+	int i;
+	int error = 0;
+
+	if (head->fmh_iflags & ~FMH_IF_VALID)
+		return -EINVAL;
+	if (!ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[0]) ||
+	    !ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[1]))
+		return -EINVAL;
+
+	head->fmh_entries = 0;
+
+	/* Set up our device handlers. */
+	memset(handlers, 0, sizeof(handlers));
+	handlers[0].gfd_dev = new_encode_dev(sb->s_bdev->bd_dev);
+	handlers[0].gfd_fn = ext4_getfsmap_datadev;
+	if (EXT4_SB(sb)->s_journal_bdev_file) {
+		handlers[1].gfd_dev = new_encode_dev(
+			file_bdev(EXT4_SB(sb)->s_journal_bdev_file)->bd_dev);
+		handlers[1].gfd_fn = ext4_getfsmap_logdev;
+	}
+
+	sort(handlers, EXT4_GETFSMAP_DEVS, sizeof(struct ext4_getfsmap_dev),
+			ext4_getfsmap_dev_compare, NULL);
+
+	/*
+	 * To continue where we left off, we allow userspace to use the
+	 * last mapping from a previous call as the low key of the next.
+	 * This is identified by a non-zero length in the low key. We
+	 * have to increment the low key in this scenario to ensure we
+	 * don't return the same mapping again, and instead return the
+	 * very next mapping.
+	 *
+	 * Bump the physical offset as there can be no other mapping for
+	 * the same physical block range.
+	 */
+	dkeys[0] = head->fmh_keys[0];
+	dkeys[0].fmr_physical += dkeys[0].fmr_length;
+	dkeys[0].fmr_owner = 0;
+	dkeys[0].fmr_length = 0;
+	memset(&dkeys[1], 0xFF, sizeof(struct ext4_fsmap));
+
+	if (!ext4_getfsmap_check_keys(dkeys, &head->fmh_keys[1]))
+		return -EINVAL;
+
+	info.gfi_next_fsblk = head->fmh_keys[0].fmr_physical +
+			  head->fmh_keys[0].fmr_length;
+	info.gfi_formatter = formatter;
+	info.gfi_format_arg = arg;
+	info.gfi_head = head;
+
+	/* For each device we support... */
+	for (i = 0; i < EXT4_GETFSMAP_DEVS; i++) {
+		/* Is this device within the range the user asked for? */
+		if (!handlers[i].gfd_fn)
+			continue;
+		if (head->fmh_keys[0].fmr_device > handlers[i].gfd_dev)
+			continue;
+		if (head->fmh_keys[1].fmr_device < handlers[i].gfd_dev)
+			break;
+
+		/*
+		 * If this device number matches the high key, we have
+		 * to pass the high key to the handler to limit the
+		 * query results.  If the device number exceeds the
+		 * low key, zero out the low key so that we get
+		 * everything from the beginning.
+		 */
+		if (handlers[i].gfd_dev == head->fmh_keys[1].fmr_device)
+			dkeys[1] = head->fmh_keys[1];
+		if (handlers[i].gfd_dev > head->fmh_keys[0].fmr_device)
+			memset(&dkeys[0], 0, sizeof(struct ext4_fsmap));
+
+		info.gfi_dev = handlers[i].gfd_dev;
+		info.gfi_last = false;
+		info.gfi_agno = -1;
+		error = handlers[i].gfd_fn(sb, dkeys, &info);
+		if (error)
+			break;
+		info.gfi_next_fsblk = 0;
+	}
+
+	head->fmh_oflags = FMH_OF_DEV_T;
+	return error;
+}