Merge tag 'xfs-6.10-merge-6' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull xfs updates from Chandan Babu:
 "Online repair feature continues to be expanded. Also, we now support
  delayed allocation for realtime devices which have an extent size that
  is equal to filesystem's block size.

  New code:

   - Introduce Parent Pointer extended attribute for inodes

   - Bring back delalloc support for realtime devices which have an
     extent size that is equal to filesystem's block size

   - Improve performance of log incompat feature handling

  Online Repair:

   - Implement atomic file content exchanges i.e. exchange ranges of
     bytes between two files atomically

   - Create temporary files to repair file-based metadata. This uses
     atomic file content exchange facility to swap file fork mappings
     between the temporary file and the metadata inode

   - Allow callers of directory/xattr code to set an explicit owner
     number to be written into the header fields of any new blocks that
     are created. This is required to avoid walking every block of the
     new structure and modify their ownership during online repair

   - Repair more data structures:
       - Extended attributes
       - Inode unlinked state
       - Directories
       - Symbolic links
       - AGI's unlinked inode list
       - Parent pointers

   - Move Orphan files to lost and found directory

   - Fixes for Inode repair functionality

   - Introduce a new sub-AG FITRIM implementation to reduce the duration
     for which the AGF lock is held

   - Updates for the design documentation

   - Use Parent Pointers to assist in checking directories, parent
     pointers, extended attributes, and link counts

  Fixes:

   - Prevent userspace from reading invalid file data due to incorrect.
     updation of file size when performing a non-atomic clone operation

   - Minor fixes to online repair

   - Fix confusing return values from xfs_bmapi_write()

   - Fix an out of bounds access due to incorrect h_size during log
     recovery

   - Defer upgrading the extent counters in xfs_reflink_end_cow_extent()
     until we know we are going to modify the extent mapping

   - Remove racy access to if_bytes check in
     xfs_reflink_end_cow_extent()

   - Fix sparse warnings

  Cleanups:

   - Hold inode locks on all files involved in a rename until the
     completion of the operation. This is in preparation for the parent
     pointers patchset where parent pointers are applied in a separate
     chained update from the actual directory update

   - Compile out v4 support when disabled

   - Cleanup xfs_extent_busy_clear()

   - Remove unused flags and fields from struct xfs_da_args

   - Remove definitions of unused functions

   - Improve extended attribute validation

   - Add higher level directory operations helpers to remove duplication
     of code

   - Cleanup quota (un)reservation interfaces"

* tag 'xfs-6.10-merge-6' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (221 commits)
  xfs: simplify iext overflow checking and upgrade
  xfs: remove a racy if_bytes check in xfs_reflink_end_cow_extent
  xfs: upgrade the extent counters in xfs_reflink_end_cow_extent later
  xfs: xfs_quota_unreserve_blkres can't fail
  xfs: consolidate the xfs_quota_reserve_blkres definitions
  xfs: clean up buffer allocation in xlog_do_recovery_pass
  xfs: fix log recovery buffer allocation for the legacy h_size fixup
  xfs: widen flags argument to the xfs_iflags_* helpers
  xfs: minor cleanups of xfs_attr3_rmt_blocks
  xfs: create a helper to compute the blockcount of a max sized remote value
  xfs: turn XFS_ATTR3_RMT_BUF_SPACE into a function
  xfs: use unsigned ints for non-negative quantities in xfs_attr_remote.c
  xfs: do not allocate the entire delalloc extent in xfs_bmapi_write
  xfs: fix xfs_bmap_add_extent_delay_real for partial conversions
  xfs: remove the xfs_iext_peek_prev_extent call in xfs_bmapi_allocate
  xfs: pass the actual offset and len to allocate to xfs_bmapi_allocate
  xfs: don't open code XFS_FILBLKS_MIN in xfs_bmapi_write
  xfs: lift a xfs_valid_startblock into xfs_bmapi_allocate
  xfs: remove the unusued tmp_logflags variable in xfs_bmapi_allocate
  xfs: fix error returns from xfs_bmapi_write
  ...

1 files changed, 804 insertions, 0 deletions

diff --git a/fs/xfs/xfs_exchrange.c b/fs/xfs/xfs_exchrange.c
new file mode 100644
index 0000000000000..c8a655c92c92f
--- /dev/null
+++ b/fs/xfs/xfs_exchrange.c
@@ -0,0 +1,804 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2020-2024 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#include "xfs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_log_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_inode.h"
+#include "xfs_trans.h"
+#include "xfs_quota.h"
+#include "xfs_bmap_util.h"
+#include "xfs_reflink.h"
+#include "xfs_trace.h"
+#include "xfs_exchrange.h"
+#include "xfs_exchmaps.h"
+#include "xfs_sb.h"
+#include "xfs_icache.h"
+#include "xfs_log.h"
+#include "xfs_rtbitmap.h"
+#include <linux/fsnotify.h>
+
+/* Lock (and optionally join) two inodes for a file range exchange. */
+void
+xfs_exchrange_ilock(
+	struct xfs_trans	*tp,
+	struct xfs_inode	*ip1,
+	struct xfs_inode	*ip2)
+{
+	if (ip1 != ip2)
+		xfs_lock_two_inodes(ip1, XFS_ILOCK_EXCL,
+				    ip2, XFS_ILOCK_EXCL);
+	else
+		xfs_ilock(ip1, XFS_ILOCK_EXCL);
+	if (tp) {
+		xfs_trans_ijoin(tp, ip1, 0);
+		if (ip2 != ip1)
+			xfs_trans_ijoin(tp, ip2, 0);
+	}
+
+}
+
+/* Unlock two inodes after a file range exchange operation. */
+void
+xfs_exchrange_iunlock(
+	struct xfs_inode	*ip1,
+	struct xfs_inode	*ip2)
+{
+	if (ip2 != ip1)
+		xfs_iunlock(ip2, XFS_ILOCK_EXCL);
+	xfs_iunlock(ip1, XFS_ILOCK_EXCL);
+}
+
+/*
+ * Estimate the resource requirements to exchange file contents between the two
+ * files.  The caller is required to hold the IOLOCK and the MMAPLOCK and to
+ * have flushed both inodes' pagecache and active direct-ios.
+ */
+int
+xfs_exchrange_estimate(
+	struct xfs_exchmaps_req	*req)
+{
+	int			error;
+
+	xfs_exchrange_ilock(NULL, req->ip1, req->ip2);
+	error = xfs_exchmaps_estimate(req);
+	xfs_exchrange_iunlock(req->ip1, req->ip2);
+	return error;
+}
+
+#define QRETRY_IP1	(0x1)
+#define QRETRY_IP2	(0x2)
+
+/*
+ * Obtain a quota reservation to make sure we don't hit EDQUOT.  We can skip
+ * this if quota enforcement is disabled or if both inodes' dquots are the
+ * same.  The qretry structure must be initialized to zeroes before the first
+ * call to this function.
+ */
+STATIC int
+xfs_exchrange_reserve_quota(
+	struct xfs_trans		*tp,
+	const struct xfs_exchmaps_req	*req,
+	unsigned int			*qretry)
+{
+	int64_t				ddelta, rdelta;
+	int				ip1_error = 0;
+	int				error;
+
+	/*
+	 * Don't bother with a quota reservation if we're not enforcing them
+	 * or the two inodes have the same dquots.
+	 */
+	if (!XFS_IS_QUOTA_ON(tp->t_mountp) || req->ip1 == req->ip2 ||
+	    (req->ip1->i_udquot == req->ip2->i_udquot &&
+	     req->ip1->i_gdquot == req->ip2->i_gdquot &&
+	     req->ip1->i_pdquot == req->ip2->i_pdquot))
+		return 0;
+
+	*qretry = 0;
+
+	/*
+	 * For each file, compute the net gain in the number of regular blocks
+	 * that will be mapped into that file and reserve that much quota.  The
+	 * quota counts must be able to absorb at least that much space.
+	 */
+	ddelta = req->ip2_bcount - req->ip1_bcount;
+	rdelta = req->ip2_rtbcount - req->ip1_rtbcount;
+	if (ddelta > 0 || rdelta > 0) {
+		error = xfs_trans_reserve_quota_nblks(tp, req->ip1,
+				ddelta > 0 ? ddelta : 0,
+				rdelta > 0 ? rdelta : 0,
+				false);
+		if (error == -EDQUOT || error == -ENOSPC) {
+			/*
+			 * Save this error and see what happens if we try to
+			 * reserve quota for ip2.  Then report both.
+			 */
+			*qretry |= QRETRY_IP1;
+			ip1_error = error;
+			error = 0;
+		}
+		if (error)
+			return error;
+	}
+	if (ddelta < 0 || rdelta < 0) {
+		error = xfs_trans_reserve_quota_nblks(tp, req->ip2,
+				ddelta < 0 ? -ddelta : 0,
+				rdelta < 0 ? -rdelta : 0,
+				false);
+		if (error == -EDQUOT || error == -ENOSPC)
+			*qretry |= QRETRY_IP2;
+		if (error)
+			return error;
+	}
+	if (ip1_error)
+		return ip1_error;
+
+	/*
+	 * For each file, forcibly reserve the gross gain in mapped blocks so
+	 * that we don't trip over any quota block reservation assertions.
+	 * We must reserve the gross gain because the quota code subtracts from
+	 * bcount the number of blocks that we unmap; it does not add that
+	 * quantity back to the quota block reservation.
+	 */
+	error = xfs_trans_reserve_quota_nblks(tp, req->ip1, req->ip1_bcount,
+			req->ip1_rtbcount, true);
+	if (error)
+		return error;
+
+	return xfs_trans_reserve_quota_nblks(tp, req->ip2, req->ip2_bcount,
+			req->ip2_rtbcount, true);
+}
+
+/* Exchange the mappings (and hence the contents) of two files' forks. */
+STATIC int
+xfs_exchrange_mappings(
+	const struct xfs_exchrange	*fxr,
+	struct xfs_inode		*ip1,
+	struct xfs_inode		*ip2)
+{
+	struct xfs_mount		*mp = ip1->i_mount;
+	struct xfs_exchmaps_req		req = {
+		.ip1			= ip1,
+		.ip2			= ip2,
+		.startoff1		= XFS_B_TO_FSBT(mp, fxr->file1_offset),
+		.startoff2		= XFS_B_TO_FSBT(mp, fxr->file2_offset),
+		.blockcount		= XFS_B_TO_FSB(mp, fxr->length),
+	};
+	struct xfs_trans		*tp;
+	unsigned int			qretry;
+	bool				retried = false;
+	int				error;
+
+	trace_xfs_exchrange_mappings(fxr, ip1, ip2);
+
+	if (fxr->flags & XFS_EXCHANGE_RANGE_TO_EOF)
+		req.flags |= XFS_EXCHMAPS_SET_SIZES;
+	if (fxr->flags & XFS_EXCHANGE_RANGE_FILE1_WRITTEN)
+		req.flags |= XFS_EXCHMAPS_INO1_WRITTEN;
+
+	/*
+	 * Round the request length up to the nearest file allocation unit.
+	 * The prep function already checked that the request offsets and
+	 * length in @fxr are safe to round up.
+	 */
+	if (xfs_inode_has_bigrtalloc(ip2))
+		req.blockcount = xfs_rtb_roundup_rtx(mp, req.blockcount);
+
+	error = xfs_exchrange_estimate(&req);
+	if (error)
+		return error;
+
+retry:
+	/* Allocate the transaction, lock the inodes, and join them. */
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, req.resblks, 0,
+			XFS_TRANS_RES_FDBLKS, &tp);
+	if (error)
+		return error;
+
+	xfs_exchrange_ilock(tp, ip1, ip2);
+
+	trace_xfs_exchrange_before(ip2, 2);
+	trace_xfs_exchrange_before(ip1, 1);
+
+	error = xfs_exchmaps_check_forks(mp, &req);
+	if (error)
+		goto out_trans_cancel;
+
+	/*
+	 * Reserve ourselves some quota if any of them are in enforcing mode.
+	 * In theory we only need enough to satisfy the change in the number
+	 * of blocks between the two ranges being remapped.
+	 */
+	error = xfs_exchrange_reserve_quota(tp, &req, &qretry);
+	if ((error == -EDQUOT || error == -ENOSPC) && !retried) {
+		xfs_trans_cancel(tp);
+		xfs_exchrange_iunlock(ip1, ip2);
+		if (qretry & QRETRY_IP1)
+			xfs_blockgc_free_quota(ip1, 0);
+		if (qretry & QRETRY_IP2)
+			xfs_blockgc_free_quota(ip2, 0);
+		retried = true;
+		goto retry;
+	}
+	if (error)
+		goto out_trans_cancel;
+
+	/* If we got this far on a dry run, all parameters are ok. */
+	if (fxr->flags & XFS_EXCHANGE_RANGE_DRY_RUN)
+		goto out_trans_cancel;
+
+	/* Update the mtime and ctime of both files. */
+	if (fxr->flags & __XFS_EXCHANGE_RANGE_UPD_CMTIME1)
+		xfs_trans_ichgtime(tp, ip1, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
+	if (fxr->flags & __XFS_EXCHANGE_RANGE_UPD_CMTIME2)
+		xfs_trans_ichgtime(tp, ip2, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
+
+	xfs_exchange_mappings(tp, &req);
+
+	/*
+	 * Force the log to persist metadata updates if the caller or the
+	 * administrator requires this.  The generic prep function already
+	 * flushed the relevant parts of the page cache.
+	 */
+	if (xfs_has_wsync(mp) || (fxr->flags & XFS_EXCHANGE_RANGE_DSYNC))
+		xfs_trans_set_sync(tp);
+
+	error = xfs_trans_commit(tp);
+
+	trace_xfs_exchrange_after(ip2, 2);
+	trace_xfs_exchrange_after(ip1, 1);
+
+	if (error)
+		goto out_unlock;
+
+	/*
+	 * If the caller wanted us to exchange the contents of two complete
+	 * files of unequal length, exchange the incore sizes now.  This should
+	 * be safe because we flushed both files' page caches, exchanged all
+	 * the mappings, and updated the ondisk sizes.
+	 */
+	if (fxr->flags & XFS_EXCHANGE_RANGE_TO_EOF) {
+		loff_t	temp;
+
+		temp = i_size_read(VFS_I(ip2));
+		i_size_write(VFS_I(ip2), i_size_read(VFS_I(ip1)));
+		i_size_write(VFS_I(ip1), temp);
+	}
+
+out_unlock:
+	xfs_exchrange_iunlock(ip1, ip2);
+	return error;
+
+out_trans_cancel:
+	xfs_trans_cancel(tp);
+	goto out_unlock;
+}
+
+/*
+ * Generic code for exchanging ranges of two files via XFS_IOC_EXCHANGE_RANGE.
+ * This part deals with struct file objects and byte ranges and does not deal
+ * with XFS-specific data structures such as xfs_inodes and block ranges.  This
+ * separation may some day facilitate porting to another filesystem.
+ *
+ * The goal is to exchange fxr.length bytes starting at fxr.file1_offset in
+ * file1 with the same number of bytes starting at fxr.file2_offset in file2.
+ * Implementations must call xfs_exchange_range_prep to prepare the two
+ * files prior to taking locks; and they must update the inode change and mod
+ * times of both files as part of the metadata update.  The timestamp update
+ * and freshness checks must be done atomically as part of the data exchange
+ * operation to ensure correctness of the freshness check.
+ * xfs_exchange_range_finish must be called after the operation completes
+ * successfully but before locks are dropped.
+ */
+
+/* Verify that we have security clearance to perform this operation. */
+static int
+xfs_exchange_range_verify_area(
+	struct xfs_exchrange	*fxr)
+{
+	int			ret;
+
+	ret = remap_verify_area(fxr->file1, fxr->file1_offset, fxr->length,
+			true);
+	if (ret)
+		return ret;
+
+	return remap_verify_area(fxr->file2, fxr->file2_offset, fxr->length,
+			true);
+}
+
+/*
+ * Performs necessary checks before doing a range exchange, having stabilized
+ * mutable inode attributes via i_rwsem.
+ */
+static inline int
+xfs_exchange_range_checks(
+	struct xfs_exchrange	*fxr,
+	unsigned int		alloc_unit)
+{
+	struct inode		*inode1 = file_inode(fxr->file1);
+	struct inode		*inode2 = file_inode(fxr->file2);
+	uint64_t		allocmask = alloc_unit - 1;
+	int64_t			test_len;
+	uint64_t		blen;
+	loff_t			size1, size2, tmp;
+	int			error;
+
+	/* Don't touch certain kinds of inodes */
+	if (IS_IMMUTABLE(inode1) || IS_IMMUTABLE(inode2))
+		return -EPERM;
+	if (IS_SWAPFILE(inode1) || IS_SWAPFILE(inode2))
+		return -ETXTBSY;
+
+	size1 = i_size_read(inode1);
+	size2 = i_size_read(inode2);
+
+	/* Ranges cannot start after EOF. */
+	if (fxr->file1_offset > size1 || fxr->file2_offset > size2)
+		return -EINVAL;
+
+	/*
+	 * If the caller said to exchange to EOF, we set the length of the
+	 * request large enough to cover everything to the end of both files.
+	 */
+	if (fxr->flags & XFS_EXCHANGE_RANGE_TO_EOF) {
+		fxr->length = max_t(int64_t, size1 - fxr->file1_offset,
+					     size2 - fxr->file2_offset);
+
+		error = xfs_exchange_range_verify_area(fxr);
+		if (error)
+			return error;
+	}
+
+	/*
+	 * The start of both ranges must be aligned to the file allocation
+	 * unit.
+	 */
+	if (!IS_ALIGNED(fxr->file1_offset, alloc_unit) ||
+	    !IS_ALIGNED(fxr->file2_offset, alloc_unit))
+		return -EINVAL;
+
+	/* Ensure offsets don't wrap. */
+	if (check_add_overflow(fxr->file1_offset, fxr->length, &tmp) ||
+	    check_add_overflow(fxr->file2_offset, fxr->length, &tmp))
+		return -EINVAL;
+
+	/*
+	 * We require both ranges to end within EOF, unless we're exchanging
+	 * to EOF.
+	 */
+	if (!(fxr->flags & XFS_EXCHANGE_RANGE_TO_EOF) &&
+	    (fxr->file1_offset + fxr->length > size1 ||
+	     fxr->file2_offset + fxr->length > size2))
+		return -EINVAL;
+
+	/*
+	 * Make sure we don't hit any file size limits.  If we hit any size
+	 * limits such that test_length was adjusted, we abort the whole
+	 * operation.
+	 */
+	test_len = fxr->length;
+	error = generic_write_check_limits(fxr->file2, fxr->file2_offset,
+			&test_len);
+	if (error)
+		return error;
+	error = generic_write_check_limits(fxr->file1, fxr->file1_offset,
+			&test_len);
+	if (error)
+		return error;
+	if (test_len != fxr->length)
+		return -EINVAL;
+
+	/*
+	 * If the user wanted us to exchange up to the infile's EOF, round up
+	 * to the next allocation unit boundary for this check.  Do the same
+	 * for the outfile.
+	 *
+	 * Otherwise, reject the range length if it's not aligned to an
+	 * allocation unit.
+	 */
+	if (fxr->file1_offset + fxr->length == size1)
+		blen = ALIGN(size1, alloc_unit) - fxr->file1_offset;
+	else if (fxr->file2_offset + fxr->length == size2)
+		blen = ALIGN(size2, alloc_unit) - fxr->file2_offset;
+	else if (!IS_ALIGNED(fxr->length, alloc_unit))
+		return -EINVAL;
+	else
+		blen = fxr->length;
+
+	/* Don't allow overlapped exchanges within the same file. */
+	if (inode1 == inode2 &&
+	    fxr->file2_offset + blen > fxr->file1_offset &&
+	    fxr->file1_offset + blen > fxr->file2_offset)
+		return -EINVAL;
+
+	/*
+	 * Ensure that we don't exchange a partial EOF block into the middle of
+	 * another file.
+	 */
+	if ((fxr->length & allocmask) == 0)
+		return 0;
+
+	blen = fxr->length;
+	if (fxr->file2_offset + blen < size2)
+		blen &= ~allocmask;
+
+	if (fxr->file1_offset + blen < size1)
+		blen &= ~allocmask;
+
+	return blen == fxr->length ? 0 : -EINVAL;
+}
+
+/*
+ * Check that the two inodes are eligible for range exchanges, the ranges make
+ * sense, and then flush all dirty data.  Caller must ensure that the inodes
+ * have been locked against any other modifications.
+ */
+static inline int
+xfs_exchange_range_prep(
+	struct xfs_exchrange	*fxr,
+	unsigned int		alloc_unit)
+{
+	struct inode		*inode1 = file_inode(fxr->file1);
+	struct inode		*inode2 = file_inode(fxr->file2);
+	bool			same_inode = (inode1 == inode2);
+	int			error;
+
+	/* Check that we don't violate system file offset limits. */
+	error = xfs_exchange_range_checks(fxr, alloc_unit);
+	if (error || fxr->length == 0)
+		return error;
+
+	/* Wait for the completion of any pending IOs on both files */
+	inode_dio_wait(inode1);
+	if (!same_inode)
+		inode_dio_wait(inode2);
+
+	error = filemap_write_and_wait_range(inode1->i_mapping,
+			fxr->file1_offset,
+			fxr->file1_offset + fxr->length - 1);
+	if (error)
+		return error;
+
+	error = filemap_write_and_wait_range(inode2->i_mapping,
+			fxr->file2_offset,
+			fxr->file2_offset + fxr->length - 1);
+	if (error)
+		return error;
+
+	/*
+	 * If the files or inodes involved require synchronous writes, amend
+	 * the request to force the filesystem to flush all data and metadata
+	 * to disk after the operation completes.
+	 */
+	if (((fxr->file1->f_flags | fxr->file2->f_flags) & O_SYNC) ||
+	    IS_SYNC(inode1) || IS_SYNC(inode2))
+		fxr->flags |= XFS_EXCHANGE_RANGE_DSYNC;
+
+	return 0;
+}
+
+/*
+ * Finish a range exchange operation, if it was successful.  Caller must ensure
+ * that the inodes are still locked against any other modifications.
+ */
+static inline int
+xfs_exchange_range_finish(
+	struct xfs_exchrange	*fxr)
+{
+	int			error;
+
+	error = file_remove_privs(fxr->file1);
+	if (error)
+		return error;
+	if (file_inode(fxr->file1) == file_inode(fxr->file2))
+		return 0;
+
+	return file_remove_privs(fxr->file2);
+}
+
+/*
+ * Check the alignment of an exchange request when the allocation unit size
+ * isn't a power of two.  The generic file-level helpers use (fast)
+ * bitmask-based alignment checks, but here we have to use slow long division.
+ */
+static int
+xfs_exchrange_check_rtalign(
+	const struct xfs_exchrange	*fxr,
+	struct xfs_inode		*ip1,
+	struct xfs_inode		*ip2,
+	unsigned int			alloc_unit)
+{
+	uint64_t			length = fxr->length;
+	uint64_t			blen;
+	loff_t				size1, size2;
+
+	size1 = i_size_read(VFS_I(ip1));
+	size2 = i_size_read(VFS_I(ip2));
+
+	/* The start of both ranges must be aligned to a rt extent. */
+	if (!isaligned_64(fxr->file1_offset, alloc_unit) ||
+	    !isaligned_64(fxr->file2_offset, alloc_unit))
+		return -EINVAL;
+
+	if (fxr->flags & XFS_EXCHANGE_RANGE_TO_EOF)
+		length = max_t(int64_t, size1 - fxr->file1_offset,
+					size2 - fxr->file2_offset);
+
+	/*
+	 * If the user wanted us to exchange up to the infile's EOF, round up
+	 * to the next rt extent boundary for this check.  Do the same for the
+	 * outfile.
+	 *
+	 * Otherwise, reject the range length if it's not rt extent aligned.
+	 * We already confirmed the starting offsets' rt extent block
+	 * alignment.
+	 */
+	if (fxr->file1_offset + length == size1)
+		blen = roundup_64(size1, alloc_unit) - fxr->file1_offset;
+	else if (fxr->file2_offset + length == size2)
+		blen = roundup_64(size2, alloc_unit) - fxr->file2_offset;
+	else if (!isaligned_64(length, alloc_unit))
+		return -EINVAL;
+	else
+		blen = length;
+
+	/* Don't allow overlapped exchanges within the same file. */
+	if (ip1 == ip2 &&
+	    fxr->file2_offset + blen > fxr->file1_offset &&
+	    fxr->file1_offset + blen > fxr->file2_offset)
+		return -EINVAL;
+
+	/*
+	 * Ensure that we don't exchange a partial EOF rt extent into the
+	 * middle of another file.
+	 */
+	if (isaligned_64(length, alloc_unit))
+		return 0;
+
+	blen = length;
+	if (fxr->file2_offset + length < size2)
+		blen = rounddown_64(blen, alloc_unit);
+
+	if (fxr->file1_offset + blen < size1)
+		blen = rounddown_64(blen, alloc_unit);
+
+	return blen == length ? 0 : -EINVAL;
+}
+
+/* Prepare two files to have their data exchanged. */
+STATIC int
+xfs_exchrange_prep(
+	struct xfs_exchrange	*fxr,
+	struct xfs_inode	*ip1,
+	struct xfs_inode	*ip2)
+{
+	struct xfs_mount	*mp = ip2->i_mount;
+	unsigned int		alloc_unit = xfs_inode_alloc_unitsize(ip2);
+	int			error;
+
+	trace_xfs_exchrange_prep(fxr, ip1, ip2);
+
+	/* Verify both files are either real-time or non-realtime */
+	if (XFS_IS_REALTIME_INODE(ip1) != XFS_IS_REALTIME_INODE(ip2))
+		return -EINVAL;
+
+	/* Check non-power of two alignment issues, if necessary. */
+	if (!is_power_of_2(alloc_unit)) {
+		error = xfs_exchrange_check_rtalign(fxr, ip1, ip2, alloc_unit);
+		if (error)
+			return error;
+
+		/*
+		 * Do the generic file-level checks with the regular block
+		 * alignment.
+		 */
+		alloc_unit = mp->m_sb.sb_blocksize;
+	}
+
+	error = xfs_exchange_range_prep(fxr, alloc_unit);
+	if (error || fxr->length == 0)
+		return error;
+
+	/* Attach dquots to both inodes before changing block maps. */
+	error = xfs_qm_dqattach(ip2);
+	if (error)
+		return error;
+	error = xfs_qm_dqattach(ip1);
+	if (error)
+		return error;
+
+	trace_xfs_exchrange_flush(fxr, ip1, ip2);
+
+	/* Flush the relevant ranges of both files. */
+	error = xfs_flush_unmap_range(ip2, fxr->file2_offset, fxr->length);
+	if (error)
+		return error;
+	error = xfs_flush_unmap_range(ip1, fxr->file1_offset, fxr->length);
+	if (error)
+		return error;
+
+	/*
+	 * Cancel CoW fork preallocations for the ranges of both files.  The
+	 * prep function should have flushed all the dirty data, so the only
+	 * CoW mappings remaining should be speculative.
+	 */
+	if (xfs_inode_has_cow_data(ip1)) {
+		error = xfs_reflink_cancel_cow_range(ip1, fxr->file1_offset,
+				fxr->length, true);
+		if (error)
+			return error;
+	}
+
+	if (xfs_inode_has_cow_data(ip2)) {
+		error = xfs_reflink_cancel_cow_range(ip2, fxr->file2_offset,
+				fxr->length, true);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+/*
+ * Exchange contents of files.  This is the binding between the generic
+ * file-level concepts and the XFS inode-specific implementation.
+ */
+STATIC int
+xfs_exchrange_contents(
+	struct xfs_exchrange	*fxr)
+{
+	struct inode		*inode1 = file_inode(fxr->file1);
+	struct inode		*inode2 = file_inode(fxr->file2);
+	struct xfs_inode	*ip1 = XFS_I(inode1);
+	struct xfs_inode	*ip2 = XFS_I(inode2);
+	struct xfs_mount	*mp = ip1->i_mount;
+	int			error;
+
+	if (!xfs_has_exchange_range(mp))
+		return -EOPNOTSUPP;
+
+	if (fxr->flags & ~(XFS_EXCHANGE_RANGE_ALL_FLAGS |
+			   XFS_EXCHANGE_RANGE_PRIV_FLAGS))
+		return -EINVAL;
+
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+
+	/* Lock both files against IO */
+	error = xfs_ilock2_io_mmap(ip1, ip2);
+	if (error)
+		goto out_err;
+
+	/* Prepare and then exchange file contents. */
+	error = xfs_exchrange_prep(fxr, ip1, ip2);
+	if (error)
+		goto out_unlock;
+
+	error = xfs_exchrange_mappings(fxr, ip1, ip2);
+	if (error)
+		goto out_unlock;
+
+	/*
+	 * Finish the exchange by removing special file privileges like any
+	 * other file write would do.  This may involve turning on support for
+	 * logged xattrs if either file has security capabilities.
+	 */
+	error = xfs_exchange_range_finish(fxr);
+	if (error)
+		goto out_unlock;
+
+out_unlock:
+	xfs_iunlock2_io_mmap(ip1, ip2);
+out_err:
+	if (error)
+		trace_xfs_exchrange_error(ip2, error, _RET_IP_);
+	return error;
+}
+
+/* Exchange parts of two files. */
+static int
+xfs_exchange_range(
+	struct xfs_exchrange	*fxr)
+{
+	struct inode		*inode1 = file_inode(fxr->file1);
+	struct inode		*inode2 = file_inode(fxr->file2);
+	int			ret;
+
+	BUILD_BUG_ON(XFS_EXCHANGE_RANGE_ALL_FLAGS &
+		     XFS_EXCHANGE_RANGE_PRIV_FLAGS);
+
+	/* Both files must be on the same mount/filesystem. */
+	if (fxr->file1->f_path.mnt != fxr->file2->f_path.mnt)
+		return -EXDEV;
+
+	if (fxr->flags & ~XFS_EXCHANGE_RANGE_ALL_FLAGS)
+		return -EINVAL;
+
+	/* Userspace requests only honored for regular files. */
+	if (S_ISDIR(inode1->i_mode) || S_ISDIR(inode2->i_mode))
+		return -EISDIR;
+	if (!S_ISREG(inode1->i_mode) || !S_ISREG(inode2->i_mode))
+		return -EINVAL;
+
+	/* Both files must be opened for read and write. */
+	if (!(fxr->file1->f_mode & FMODE_READ) ||
+	    !(fxr->file1->f_mode & FMODE_WRITE) ||
+	    !(fxr->file2->f_mode & FMODE_READ) ||
+	    !(fxr->file2->f_mode & FMODE_WRITE))
+		return -EBADF;
+
+	/* Neither file can be opened append-only. */
+	if ((fxr->file1->f_flags & O_APPEND) ||
+	    (fxr->file2->f_flags & O_APPEND))
+		return -EBADF;
+
+	/*
+	 * If we're not exchanging to EOF, we can check the areas before
+	 * stabilizing both files' i_size.
+	 */
+	if (!(fxr->flags & XFS_EXCHANGE_RANGE_TO_EOF)) {
+		ret = xfs_exchange_range_verify_area(fxr);
+		if (ret)
+			return ret;
+	}
+
+	/* Update cmtime if the fd/inode don't forbid it. */
+	if (!(fxr->file1->f_mode & FMODE_NOCMTIME) && !IS_NOCMTIME(inode1))
+		fxr->flags |= __XFS_EXCHANGE_RANGE_UPD_CMTIME1;
+	if (!(fxr->file2->f_mode & FMODE_NOCMTIME) && !IS_NOCMTIME(inode2))
+		fxr->flags |= __XFS_EXCHANGE_RANGE_UPD_CMTIME2;
+
+	file_start_write(fxr->file2);
+	ret = xfs_exchrange_contents(fxr);
+	file_end_write(fxr->file2);
+	if (ret)
+		return ret;
+
+	fsnotify_modify(fxr->file1);
+	if (fxr->file2 != fxr->file1)
+		fsnotify_modify(fxr->file2);
+	return 0;
+}
+
+/* Collect exchange-range arguments from userspace. */
+long
+xfs_ioc_exchange_range(
+	struct file			*file,
+	struct xfs_exchange_range __user *argp)
+{
+	struct xfs_exchrange		fxr = {
+		.file2			= file,
+	};
+	struct xfs_exchange_range	args;
+	struct fd			file1;
+	int				error;
+
+	if (copy_from_user(&args, argp, sizeof(args)))
+		return -EFAULT;
+	if (memchr_inv(&args.pad, 0, sizeof(args.pad)))
+		return -EINVAL;
+	if (args.flags & ~XFS_EXCHANGE_RANGE_ALL_FLAGS)
+		return -EINVAL;
+
+	fxr.file1_offset	= args.file1_offset;
+	fxr.file2_offset	= args.file2_offset;
+	fxr.length		= args.length;
+	fxr.flags		= args.flags;
+
+	file1 = fdget(args.file1_fd);
+	if (!file1.file)
+		return -EBADF;
+	fxr.file1 = file1.file;
+
+	error = xfs_exchange_range(&fxr);
+	fdput(file1);
+	return error;
+}