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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /fs/xfs/xfs_reflink.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/xfs/xfs_reflink.c')
-rw-r--r--fs/xfs/xfs_reflink.c1720
1 files changed, 1720 insertions, 0 deletions
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
new file mode 100644
index 0000000000..eb9102453a
--- /dev/null
+++ b/fs/xfs/xfs_reflink.c
@@ -0,0 +1,1720 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2016 Oracle. All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#include "xfs.h"
+#include "xfs_fs.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_bmap.h"
+#include "xfs_bmap_util.h"
+#include "xfs_trace.h"
+#include "xfs_icache.h"
+#include "xfs_btree.h"
+#include "xfs_refcount_btree.h"
+#include "xfs_refcount.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_trans_space.h"
+#include "xfs_bit.h"
+#include "xfs_alloc.h"
+#include "xfs_quota.h"
+#include "xfs_reflink.h"
+#include "xfs_iomap.h"
+#include "xfs_ag.h"
+#include "xfs_ag_resv.h"
+
+/*
+ * Copy on Write of Shared Blocks
+ *
+ * XFS must preserve "the usual" file semantics even when two files share
+ * the same physical blocks. This means that a write to one file must not
+ * alter the blocks in a different file; the way that we'll do that is
+ * through the use of a copy-on-write mechanism. At a high level, that
+ * means that when we want to write to a shared block, we allocate a new
+ * block, write the data to the new block, and if that succeeds we map the
+ * new block into the file.
+ *
+ * XFS provides a "delayed allocation" mechanism that defers the allocation
+ * of disk blocks to dirty-but-not-yet-mapped file blocks as long as
+ * possible. This reduces fragmentation by enabling the filesystem to ask
+ * for bigger chunks less often, which is exactly what we want for CoW.
+ *
+ * The delalloc mechanism begins when the kernel wants to make a block
+ * writable (write_begin or page_mkwrite). If the offset is not mapped, we
+ * create a delalloc mapping, which is a regular in-core extent, but without
+ * a real startblock. (For delalloc mappings, the startblock encodes both
+ * a flag that this is a delalloc mapping, and a worst-case estimate of how
+ * many blocks might be required to put the mapping into the BMBT.) delalloc
+ * mappings are a reservation against the free space in the filesystem;
+ * adjacent mappings can also be combined into fewer larger mappings.
+ *
+ * As an optimization, the CoW extent size hint (cowextsz) creates
+ * outsized aligned delalloc reservations in the hope of landing out of
+ * order nearby CoW writes in a single extent on disk, thereby reducing
+ * fragmentation and improving future performance.
+ *
+ * D: --RRRRRRSSSRRRRRRRR--- (data fork)
+ * C: ------DDDDDDD--------- (CoW fork)
+ *
+ * When dirty pages are being written out (typically in writepage), the
+ * delalloc reservations are converted into unwritten mappings by
+ * allocating blocks and replacing the delalloc mapping with real ones.
+ * A delalloc mapping can be replaced by several unwritten ones if the
+ * free space is fragmented.
+ *
+ * D: --RRRRRRSSSRRRRRRRR---
+ * C: ------UUUUUUU---------
+ *
+ * We want to adapt the delalloc mechanism for copy-on-write, since the
+ * write paths are similar. The first two steps (creating the reservation
+ * and allocating the blocks) are exactly the same as delalloc except that
+ * the mappings must be stored in a separate CoW fork because we do not want
+ * to disturb the mapping in the data fork until we're sure that the write
+ * succeeded. IO completion in this case is the process of removing the old
+ * mapping from the data fork and moving the new mapping from the CoW fork to
+ * the data fork. This will be discussed shortly.
+ *
+ * For now, unaligned directio writes will be bounced back to the page cache.
+ * Block-aligned directio writes will use the same mechanism as buffered
+ * writes.
+ *
+ * Just prior to submitting the actual disk write requests, we convert
+ * the extents representing the range of the file actually being written
+ * (as opposed to extra pieces created for the cowextsize hint) to real
+ * extents. This will become important in the next step:
+ *
+ * D: --RRRRRRSSSRRRRRRRR---
+ * C: ------UUrrUUU---------
+ *
+ * CoW remapping must be done after the data block write completes,
+ * because we don't want to destroy the old data fork map until we're sure
+ * the new block has been written. Since the new mappings are kept in a
+ * separate fork, we can simply iterate these mappings to find the ones
+ * that cover the file blocks that we just CoW'd. For each extent, simply
+ * unmap the corresponding range in the data fork, map the new range into
+ * the data fork, and remove the extent from the CoW fork. Because of
+ * the presence of the cowextsize hint, however, we must be careful
+ * only to remap the blocks that we've actually written out -- we must
+ * never remap delalloc reservations nor CoW staging blocks that have
+ * yet to be written. This corresponds exactly to the real extents in
+ * the CoW fork:
+ *
+ * D: --RRRRRRrrSRRRRRRRR---
+ * C: ------UU--UUU---------
+ *
+ * Since the remapping operation can be applied to an arbitrary file
+ * range, we record the need for the remap step as a flag in the ioend
+ * instead of declaring a new IO type. This is required for direct io
+ * because we only have ioend for the whole dio, and we have to be able to
+ * remember the presence of unwritten blocks and CoW blocks with a single
+ * ioend structure. Better yet, the more ground we can cover with one
+ * ioend, the better.
+ */
+
+/*
+ * Given an AG extent, find the lowest-numbered run of shared blocks
+ * within that range and return the range in fbno/flen. If
+ * find_end_of_shared is true, return the longest contiguous extent of
+ * shared blocks. If there are no shared extents, fbno and flen will
+ * be set to NULLAGBLOCK and 0, respectively.
+ */
+static int
+xfs_reflink_find_shared(
+ struct xfs_perag *pag,
+ struct xfs_trans *tp,
+ xfs_agblock_t agbno,
+ xfs_extlen_t aglen,
+ xfs_agblock_t *fbno,
+ xfs_extlen_t *flen,
+ bool find_end_of_shared)
+{
+ struct xfs_buf *agbp;
+ struct xfs_btree_cur *cur;
+ int error;
+
+ error = xfs_alloc_read_agf(pag, tp, 0, &agbp);
+ if (error)
+ return error;
+
+ cur = xfs_refcountbt_init_cursor(pag->pag_mount, tp, agbp, pag);
+
+ error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen,
+ find_end_of_shared);
+
+ xfs_btree_del_cursor(cur, error);
+
+ xfs_trans_brelse(tp, agbp);
+ return error;
+}
+
+/*
+ * Trim the mapping to the next block where there's a change in the
+ * shared/unshared status. More specifically, this means that we
+ * find the lowest-numbered extent of shared blocks that coincides with
+ * the given block mapping. If the shared extent overlaps the start of
+ * the mapping, trim the mapping to the end of the shared extent. If
+ * the shared region intersects the mapping, trim the mapping to the
+ * start of the shared extent. If there are no shared regions that
+ * overlap, just return the original extent.
+ */
+int
+xfs_reflink_trim_around_shared(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *irec,
+ bool *shared)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_perag *pag;
+ xfs_agblock_t agbno;
+ xfs_extlen_t aglen;
+ xfs_agblock_t fbno;
+ xfs_extlen_t flen;
+ int error = 0;
+
+ /* Holes, unwritten, and delalloc extents cannot be shared */
+ if (!xfs_is_cow_inode(ip) || !xfs_bmap_is_written_extent(irec)) {
+ *shared = false;
+ return 0;
+ }
+
+ trace_xfs_reflink_trim_around_shared(ip, irec);
+
+ pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, irec->br_startblock));
+ agbno = XFS_FSB_TO_AGBNO(mp, irec->br_startblock);
+ aglen = irec->br_blockcount;
+
+ error = xfs_reflink_find_shared(pag, NULL, agbno, aglen, &fbno, &flen,
+ true);
+ xfs_perag_put(pag);
+ if (error)
+ return error;
+
+ *shared = false;
+ if (fbno == NULLAGBLOCK) {
+ /* No shared blocks at all. */
+ return 0;
+ }
+
+ if (fbno == agbno) {
+ /*
+ * The start of this extent is shared. Truncate the
+ * mapping at the end of the shared region so that a
+ * subsequent iteration starts at the start of the
+ * unshared region.
+ */
+ irec->br_blockcount = flen;
+ *shared = true;
+ return 0;
+ }
+
+ /*
+ * There's a shared extent midway through this extent.
+ * Truncate the mapping at the start of the shared
+ * extent so that a subsequent iteration starts at the
+ * start of the shared region.
+ */
+ irec->br_blockcount = fbno - agbno;
+ return 0;
+}
+
+int
+xfs_bmap_trim_cow(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *imap,
+ bool *shared)
+{
+ /* We can't update any real extents in always COW mode. */
+ if (xfs_is_always_cow_inode(ip) &&
+ !isnullstartblock(imap->br_startblock)) {
+ *shared = true;
+ return 0;
+ }
+
+ /* Trim the mapping to the nearest shared extent boundary. */
+ return xfs_reflink_trim_around_shared(ip, imap, shared);
+}
+
+static int
+xfs_reflink_convert_cow_locked(
+ struct xfs_inode *ip,
+ xfs_fileoff_t offset_fsb,
+ xfs_filblks_t count_fsb)
+{
+ struct xfs_iext_cursor icur;
+ struct xfs_bmbt_irec got;
+ struct xfs_btree_cur *dummy_cur = NULL;
+ int dummy_logflags;
+ int error = 0;
+
+ if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
+ return 0;
+
+ do {
+ if (got.br_startoff >= offset_fsb + count_fsb)
+ break;
+ if (got.br_state == XFS_EXT_NORM)
+ continue;
+ if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))
+ return -EIO;
+
+ xfs_trim_extent(&got, offset_fsb, count_fsb);
+ if (!got.br_blockcount)
+ continue;
+
+ got.br_state = XFS_EXT_NORM;
+ error = xfs_bmap_add_extent_unwritten_real(NULL, ip,
+ XFS_COW_FORK, &icur, &dummy_cur, &got,
+ &dummy_logflags);
+ if (error)
+ return error;
+ } while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));
+
+ return error;
+}
+
+/* Convert all of the unwritten CoW extents in a file's range to real ones. */
+int
+xfs_reflink_convert_cow(
+ struct xfs_inode *ip,
+ xfs_off_t offset,
+ xfs_off_t count)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
+ xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + count);
+ xfs_filblks_t count_fsb = end_fsb - offset_fsb;
+ int error;
+
+ ASSERT(count != 0);
+
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+}
+
+/*
+ * Find the extent that maps the given range in the COW fork. Even if the extent
+ * is not shared we might have a preallocation for it in the COW fork. If so we
+ * use it that rather than trigger a new allocation.
+ */
+static int
+xfs_find_trim_cow_extent(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *imap,
+ struct xfs_bmbt_irec *cmap,
+ bool *shared,
+ bool *found)
+{
+ xfs_fileoff_t offset_fsb = imap->br_startoff;
+ xfs_filblks_t count_fsb = imap->br_blockcount;
+ struct xfs_iext_cursor icur;
+
+ *found = false;
+
+ /*
+ * If we don't find an overlapping extent, trim the range we need to
+ * allocate to fit the hole we found.
+ */
+ if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, cmap))
+ cmap->br_startoff = offset_fsb + count_fsb;
+ if (cmap->br_startoff > offset_fsb) {
+ xfs_trim_extent(imap, imap->br_startoff,
+ cmap->br_startoff - imap->br_startoff);
+ return xfs_bmap_trim_cow(ip, imap, shared);
+ }
+
+ *shared = true;
+ if (isnullstartblock(cmap->br_startblock)) {
+ xfs_trim_extent(imap, cmap->br_startoff, cmap->br_blockcount);
+ return 0;
+ }
+
+ /* real extent found - no need to allocate */
+ xfs_trim_extent(cmap, offset_fsb, count_fsb);
+ *found = true;
+ return 0;
+}
+
+static int
+xfs_reflink_convert_unwritten(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *imap,
+ struct xfs_bmbt_irec *cmap,
+ bool convert_now)
+{
+ xfs_fileoff_t offset_fsb = imap->br_startoff;
+ xfs_filblks_t count_fsb = imap->br_blockcount;
+ int error;
+
+ /*
+ * cmap might larger than imap due to cowextsize hint.
+ */
+ xfs_trim_extent(cmap, offset_fsb, count_fsb);
+
+ /*
+ * COW fork extents are supposed to remain unwritten until we're ready
+ * to initiate a disk write. For direct I/O we are going to write the
+ * data and need the conversion, but for buffered writes we're done.
+ */
+ if (!convert_now || cmap->br_state == XFS_EXT_NORM)
+ return 0;
+
+ trace_xfs_reflink_convert_cow(ip, cmap);
+
+ error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
+ if (!error)
+ cmap->br_state = XFS_EXT_NORM;
+
+ return error;
+}
+
+static int
+xfs_reflink_fill_cow_hole(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *imap,
+ struct xfs_bmbt_irec *cmap,
+ bool *shared,
+ uint *lockmode,
+ bool convert_now)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ xfs_filblks_t resaligned;
+ xfs_extlen_t resblks;
+ int nimaps;
+ int error;
+ bool found;
+
+ resaligned = xfs_aligned_fsb_count(imap->br_startoff,
+ imap->br_blockcount, xfs_get_cowextsz_hint(ip));
+ resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
+
+ xfs_iunlock(ip, *lockmode);
+ *lockmode = 0;
+
+ error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, resblks, 0,
+ false, &tp);
+ if (error)
+ return error;
+
+ *lockmode = XFS_ILOCK_EXCL;
+
+ error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
+ if (error || !*shared)
+ goto out_trans_cancel;
+
+ if (found) {
+ xfs_trans_cancel(tp);
+ goto convert;
+ }
+
+ /* Allocate the entire reservation as unwritten blocks. */
+ nimaps = 1;
+ error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
+ XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0, cmap,
+ &nimaps);
+ if (error)
+ goto out_trans_cancel;
+
+ xfs_inode_set_cowblocks_tag(ip);
+ error = xfs_trans_commit(tp);
+ if (error)
+ return error;
+
+ /*
+ * Allocation succeeded but the requested range was not even partially
+ * satisfied? Bail out!
+ */
+ if (nimaps == 0)
+ return -ENOSPC;
+
+convert:
+ return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
+
+out_trans_cancel:
+ xfs_trans_cancel(tp);
+ return error;
+}
+
+static int
+xfs_reflink_fill_delalloc(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *imap,
+ struct xfs_bmbt_irec *cmap,
+ bool *shared,
+ uint *lockmode,
+ bool convert_now)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ int nimaps;
+ int error;
+ bool found;
+
+ do {
+ xfs_iunlock(ip, *lockmode);
+ *lockmode = 0;
+
+ error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, 0, 0,
+ false, &tp);
+ if (error)
+ return error;
+
+ *lockmode = XFS_ILOCK_EXCL;
+
+ error = xfs_find_trim_cow_extent(ip, imap, cmap, shared,
+ &found);
+ if (error || !*shared)
+ goto out_trans_cancel;
+
+ if (found) {
+ xfs_trans_cancel(tp);
+ break;
+ }
+
+ ASSERT(isnullstartblock(cmap->br_startblock) ||
+ cmap->br_startblock == DELAYSTARTBLOCK);
+
+ /*
+ * Replace delalloc reservation with an unwritten extent.
+ */
+ nimaps = 1;
+ error = xfs_bmapi_write(tp, ip, cmap->br_startoff,
+ cmap->br_blockcount,
+ XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0,
+ cmap, &nimaps);
+ if (error)
+ goto out_trans_cancel;
+
+ xfs_inode_set_cowblocks_tag(ip);
+ error = xfs_trans_commit(tp);
+ if (error)
+ return error;
+
+ /*
+ * Allocation succeeded but the requested range was not even
+ * partially satisfied? Bail out!
+ */
+ if (nimaps == 0)
+ return -ENOSPC;
+ } while (cmap->br_startoff + cmap->br_blockcount <= imap->br_startoff);
+
+ return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
+
+out_trans_cancel:
+ xfs_trans_cancel(tp);
+ return error;
+}
+
+/* Allocate all CoW reservations covering a range of blocks in a file. */
+int
+xfs_reflink_allocate_cow(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *imap,
+ struct xfs_bmbt_irec *cmap,
+ bool *shared,
+ uint *lockmode,
+ bool convert_now)
+{
+ int error;
+ bool found;
+
+ ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
+ if (!ip->i_cowfp) {
+ ASSERT(!xfs_is_reflink_inode(ip));
+ xfs_ifork_init_cow(ip);
+ }
+
+ error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
+ if (error || !*shared)
+ return error;
+
+ /* CoW fork has a real extent */
+ if (found)
+ return xfs_reflink_convert_unwritten(ip, imap, cmap,
+ convert_now);
+
+ /*
+ * CoW fork does not have an extent and data extent is shared.
+ * Allocate a real extent in the CoW fork.
+ */
+ if (cmap->br_startoff > imap->br_startoff)
+ return xfs_reflink_fill_cow_hole(ip, imap, cmap, shared,
+ lockmode, convert_now);
+
+ /*
+ * CoW fork has a delalloc reservation. Replace it with a real extent.
+ * There may or may not be a data fork mapping.
+ */
+ if (isnullstartblock(cmap->br_startblock) ||
+ cmap->br_startblock == DELAYSTARTBLOCK)
+ return xfs_reflink_fill_delalloc(ip, imap, cmap, shared,
+ lockmode, convert_now);
+
+ /* Shouldn't get here. */
+ ASSERT(0);
+ return -EFSCORRUPTED;
+}
+
+/*
+ * Cancel CoW reservations for some block range of an inode.
+ *
+ * If cancel_real is true this function cancels all COW fork extents for the
+ * inode; if cancel_real is false, real extents are not cleared.
+ *
+ * Caller must have already joined the inode to the current transaction. The
+ * inode will be joined to the transaction returned to the caller.
+ */
+int
+xfs_reflink_cancel_cow_blocks(
+ struct xfs_inode *ip,
+ struct xfs_trans **tpp,
+ xfs_fileoff_t offset_fsb,
+ xfs_fileoff_t end_fsb,
+ bool cancel_real)
+{
+ struct xfs_ifork *ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
+ struct xfs_bmbt_irec got, del;
+ struct xfs_iext_cursor icur;
+ int error = 0;
+
+ if (!xfs_inode_has_cow_data(ip))
+ return 0;
+ if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got))
+ return 0;
+
+ /* Walk backwards until we're out of the I/O range... */
+ while (got.br_startoff + got.br_blockcount > offset_fsb) {
+ del = got;
+ xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
+
+ /* Extent delete may have bumped ext forward */
+ if (!del.br_blockcount) {
+ xfs_iext_prev(ifp, &icur);
+ goto next_extent;
+ }
+
+ trace_xfs_reflink_cancel_cow(ip, &del);
+
+ if (isnullstartblock(del.br_startblock)) {
+ error = xfs_bmap_del_extent_delay(ip, XFS_COW_FORK,
+ &icur, &got, &del);
+ if (error)
+ break;
+ } else if (del.br_state == XFS_EXT_UNWRITTEN || cancel_real) {
+ ASSERT((*tpp)->t_highest_agno == NULLAGNUMBER);
+
+ /* Free the CoW orphan record. */
+ xfs_refcount_free_cow_extent(*tpp, del.br_startblock,
+ del.br_blockcount);
+
+ error = xfs_free_extent_later(*tpp, del.br_startblock,
+ del.br_blockcount, NULL,
+ XFS_AG_RESV_NONE);
+ if (error)
+ break;
+
+ /* Roll the transaction */
+ error = xfs_defer_finish(tpp);
+ if (error)
+ break;
+
+ /* Remove the mapping from the CoW fork. */
+ xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
+
+ /* Remove the quota reservation */
+ error = xfs_quota_unreserve_blkres(ip,
+ del.br_blockcount);
+ if (error)
+ break;
+ } else {
+ /* Didn't do anything, push cursor back. */
+ xfs_iext_prev(ifp, &icur);
+ }
+next_extent:
+ if (!xfs_iext_get_extent(ifp, &icur, &got))
+ break;
+ }
+
+ /* clear tag if cow fork is emptied */
+ if (!ifp->if_bytes)
+ xfs_inode_clear_cowblocks_tag(ip);
+ return error;
+}
+
+/*
+ * Cancel CoW reservations for some byte range of an inode.
+ *
+ * If cancel_real is true this function cancels all COW fork extents for the
+ * inode; if cancel_real is false, real extents are not cleared.
+ */
+int
+xfs_reflink_cancel_cow_range(
+ struct xfs_inode *ip,
+ xfs_off_t offset,
+ xfs_off_t count,
+ bool cancel_real)
+{
+ struct xfs_trans *tp;
+ xfs_fileoff_t offset_fsb;
+ xfs_fileoff_t end_fsb;
+ int error;
+
+ trace_xfs_reflink_cancel_cow_range(ip, offset, count);
+ ASSERT(ip->i_cowfp);
+
+ offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
+ if (count == NULLFILEOFF)
+ end_fsb = NULLFILEOFF;
+ else
+ end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
+
+ /* Start a rolling transaction to remove the mappings */
+ error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
+ 0, 0, 0, &tp);
+ if (error)
+ goto out;
+
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ xfs_trans_ijoin(tp, ip, 0);
+
+ /* Scrape out the old CoW reservations */
+ error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb,
+ cancel_real);
+ if (error)
+ goto out_cancel;
+
+ error = xfs_trans_commit(tp);
+
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+
+out_cancel:
+ xfs_trans_cancel(tp);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+out:
+ trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_);
+ return error;
+}
+
+/*
+ * Remap part of the CoW fork into the data fork.
+ *
+ * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
+ * into the data fork; this function will remap what it can (at the end of the
+ * range) and update @end_fsb appropriately. Each remap gets its own
+ * transaction because we can end up merging and splitting bmbt blocks for
+ * every remap operation and we'd like to keep the block reservation
+ * requirements as low as possible.
+ */
+STATIC int
+xfs_reflink_end_cow_extent(
+ struct xfs_inode *ip,
+ xfs_fileoff_t *offset_fsb,
+ xfs_fileoff_t end_fsb)
+{
+ struct xfs_iext_cursor icur;
+ struct xfs_bmbt_irec got, del, data;
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ struct xfs_ifork *ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
+ unsigned int resblks;
+ int nmaps;
+ int error;
+
+ /* No COW extents? That's easy! */
+ if (ifp->if_bytes == 0) {
+ *offset_fsb = end_fsb;
+ return 0;
+ }
+
+ resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
+ XFS_TRANS_RESERVE, &tp);
+ if (error)
+ return error;
+
+ /*
+ * Lock the inode. We have to ijoin without automatic unlock because
+ * the lead transaction is the refcountbt record deletion; the data
+ * fork update follows as a deferred log item.
+ */
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ xfs_trans_ijoin(tp, ip, 0);
+
+ error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+ XFS_IEXT_REFLINK_END_COW_CNT);
+ if (error == -EFBIG)
+ error = xfs_iext_count_upgrade(tp, ip,
+ XFS_IEXT_REFLINK_END_COW_CNT);
+ if (error)
+ goto out_cancel;
+
+ /*
+ * In case of racing, overlapping AIO writes no COW extents might be
+ * left by the time I/O completes for the loser of the race. In that
+ * case we are done.
+ */
+ if (!xfs_iext_lookup_extent(ip, ifp, *offset_fsb, &icur, &got) ||
+ got.br_startoff >= end_fsb) {
+ *offset_fsb = end_fsb;
+ goto out_cancel;
+ }
+
+ /*
+ * Only remap real extents that contain data. With AIO, speculative
+ * preallocations can leak into the range we are called upon, and we
+ * need to skip them. Preserve @got for the eventual CoW fork
+ * deletion; from now on @del represents the mapping that we're
+ * actually remapping.
+ */
+ while (!xfs_bmap_is_written_extent(&got)) {
+ if (!xfs_iext_next_extent(ifp, &icur, &got) ||
+ got.br_startoff >= end_fsb) {
+ *offset_fsb = end_fsb;
+ goto out_cancel;
+ }
+ }
+ del = got;
+
+ /* Grab the corresponding mapping in the data fork. */
+ nmaps = 1;
+ error = xfs_bmapi_read(ip, del.br_startoff, del.br_blockcount, &data,
+ &nmaps, 0);
+ if (error)
+ goto out_cancel;
+
+ /* We can only remap the smaller of the two extent sizes. */
+ data.br_blockcount = min(data.br_blockcount, del.br_blockcount);
+ del.br_blockcount = data.br_blockcount;
+
+ trace_xfs_reflink_cow_remap_from(ip, &del);
+ trace_xfs_reflink_cow_remap_to(ip, &data);
+
+ if (xfs_bmap_is_real_extent(&data)) {
+ /*
+ * If the extent we're remapping is backed by storage (written
+ * or not), unmap the extent and drop its refcount.
+ */
+ xfs_bmap_unmap_extent(tp, ip, &data);
+ xfs_refcount_decrease_extent(tp, &data);
+ xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
+ -data.br_blockcount);
+ } else if (data.br_startblock == DELAYSTARTBLOCK) {
+ int done;
+
+ /*
+ * If the extent we're remapping is a delalloc reservation,
+ * we can use the regular bunmapi function to release the
+ * incore state. Dropping the delalloc reservation takes care
+ * of the quota reservation for us.
+ */
+ error = xfs_bunmapi(NULL, ip, data.br_startoff,
+ data.br_blockcount, 0, 1, &done);
+ if (error)
+ goto out_cancel;
+ ASSERT(done);
+ }
+
+ /* Free the CoW orphan record. */
+ xfs_refcount_free_cow_extent(tp, del.br_startblock, del.br_blockcount);
+
+ /* Map the new blocks into the data fork. */
+ xfs_bmap_map_extent(tp, ip, &del);
+
+ /* Charge this new data fork mapping to the on-disk quota. */
+ xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
+ (long)del.br_blockcount);
+
+ /* Remove the mapping from the CoW fork. */
+ xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
+
+ error = xfs_trans_commit(tp);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ if (error)
+ return error;
+
+ /* Update the caller about how much progress we made. */
+ *offset_fsb = del.br_startoff + del.br_blockcount;
+ return 0;
+
+out_cancel:
+ xfs_trans_cancel(tp);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+}
+
+/*
+ * Remap parts of a file's data fork after a successful CoW.
+ */
+int
+xfs_reflink_end_cow(
+ struct xfs_inode *ip,
+ xfs_off_t offset,
+ xfs_off_t count)
+{
+ xfs_fileoff_t offset_fsb;
+ xfs_fileoff_t end_fsb;
+ int error = 0;
+
+ trace_xfs_reflink_end_cow(ip, offset, count);
+
+ offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
+ end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
+
+ /*
+ * Walk forwards until we've remapped the I/O range. The loop function
+ * repeatedly cycles the ILOCK to allocate one transaction per remapped
+ * extent.
+ *
+ * If we're being called by writeback then the pages will still
+ * have PageWriteback set, which prevents races with reflink remapping
+ * and truncate. Reflink remapping prevents races with writeback by
+ * taking the iolock and mmaplock before flushing the pages and
+ * remapping, which means there won't be any further writeback or page
+ * cache dirtying until the reflink completes.
+ *
+ * We should never have two threads issuing writeback for the same file
+ * region. There are also have post-eof checks in the writeback
+ * preparation code so that we don't bother writing out pages that are
+ * about to be truncated.
+ *
+ * If we're being called as part of directio write completion, the dio
+ * count is still elevated, which reflink and truncate will wait for.
+ * Reflink remapping takes the iolock and mmaplock and waits for
+ * pending dio to finish, which should prevent any directio until the
+ * remap completes. Multiple concurrent directio writes to the same
+ * region are handled by end_cow processing only occurring for the
+ * threads which succeed; the outcome of multiple overlapping direct
+ * writes is not well defined anyway.
+ *
+ * It's possible that a buffered write and a direct write could collide
+ * here (the buffered write stumbles in after the dio flushes and
+ * invalidates the page cache and immediately queues writeback), but we
+ * have never supported this 100%. If either disk write succeeds the
+ * blocks will be remapped.
+ */
+ while (end_fsb > offset_fsb && !error)
+ error = xfs_reflink_end_cow_extent(ip, &offset_fsb, end_fsb);
+
+ if (error)
+ trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
+ return error;
+}
+
+/*
+ * Free all CoW staging blocks that are still referenced by the ondisk refcount
+ * metadata. The ondisk metadata does not track which inode created the
+ * staging extent, so callers must ensure that there are no cached inodes with
+ * live CoW staging extents.
+ */
+int
+xfs_reflink_recover_cow(
+ struct xfs_mount *mp)
+{
+ struct xfs_perag *pag;
+ xfs_agnumber_t agno;
+ int error = 0;
+
+ if (!xfs_has_reflink(mp))
+ return 0;
+
+ for_each_perag(mp, agno, pag) {
+ error = xfs_refcount_recover_cow_leftovers(mp, pag);
+ if (error) {
+ xfs_perag_rele(pag);
+ break;
+ }
+ }
+
+ return error;
+}
+
+/*
+ * Reflinking (Block) Ranges of Two Files Together
+ *
+ * First, ensure that the reflink flag is set on both inodes. The flag is an
+ * optimization to avoid unnecessary refcount btree lookups in the write path.
+ *
+ * Now we can iteratively remap the range of extents (and holes) in src to the
+ * corresponding ranges in dest. Let drange and srange denote the ranges of
+ * logical blocks in dest and src touched by the reflink operation.
+ *
+ * While the length of drange is greater than zero,
+ * - Read src's bmbt at the start of srange ("imap")
+ * - If imap doesn't exist, make imap appear to start at the end of srange
+ * with zero length.
+ * - If imap starts before srange, advance imap to start at srange.
+ * - If imap goes beyond srange, truncate imap to end at the end of srange.
+ * - Punch (imap start - srange start + imap len) blocks from dest at
+ * offset (drange start).
+ * - If imap points to a real range of pblks,
+ * > Increase the refcount of the imap's pblks
+ * > Map imap's pblks into dest at the offset
+ * (drange start + imap start - srange start)
+ * - Advance drange and srange by (imap start - srange start + imap len)
+ *
+ * Finally, if the reflink made dest longer, update both the in-core and
+ * on-disk file sizes.
+ *
+ * ASCII Art Demonstration:
+ *
+ * Let's say we want to reflink this source file:
+ *
+ * ----SSSSSSS-SSSSS----SSSSSS (src file)
+ * <-------------------->
+ *
+ * into this destination file:
+ *
+ * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
+ * <-------------------->
+ * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
+ * Observe that the range has different logical offsets in either file.
+ *
+ * Consider that the first extent in the source file doesn't line up with our
+ * reflink range. Unmapping and remapping are separate operations, so we can
+ * unmap more blocks from the destination file than we remap.
+ *
+ * ----SSSSSSS-SSSSS----SSSSSS
+ * <------->
+ * --DDDDD---------DDDDD--DDD
+ * <------->
+ *
+ * Now remap the source extent into the destination file:
+ *
+ * ----SSSSSSS-SSSSS----SSSSSS
+ * <------->
+ * --DDDDD--SSSSSSSDDDDD--DDD
+ * <------->
+ *
+ * Do likewise with the second hole and extent in our range. Holes in the
+ * unmap range don't affect our operation.
+ *
+ * ----SSSSSSS-SSSSS----SSSSSS
+ * <---->
+ * --DDDDD--SSSSSSS-SSSSS-DDD
+ * <---->
+ *
+ * Finally, unmap and remap part of the third extent. This will increase the
+ * size of the destination file.
+ *
+ * ----SSSSSSS-SSSSS----SSSSSS
+ * <----->
+ * --DDDDD--SSSSSSS-SSSSS----SSS
+ * <----->
+ *
+ * Once we update the destination file's i_size, we're done.
+ */
+
+/*
+ * Ensure the reflink bit is set in both inodes.
+ */
+STATIC int
+xfs_reflink_set_inode_flag(
+ struct xfs_inode *src,
+ struct xfs_inode *dest)
+{
+ struct xfs_mount *mp = src->i_mount;
+ int error;
+ struct xfs_trans *tp;
+
+ if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
+ return 0;
+
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
+ if (error)
+ goto out_error;
+
+ /* Lock both files against IO */
+ if (src->i_ino == dest->i_ino)
+ xfs_ilock(src, XFS_ILOCK_EXCL);
+ else
+ xfs_lock_two_inodes(src, XFS_ILOCK_EXCL, dest, XFS_ILOCK_EXCL);
+
+ if (!xfs_is_reflink_inode(src)) {
+ trace_xfs_reflink_set_inode_flag(src);
+ xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
+ src->i_diflags2 |= XFS_DIFLAG2_REFLINK;
+ xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
+ xfs_ifork_init_cow(src);
+ } else
+ xfs_iunlock(src, XFS_ILOCK_EXCL);
+
+ if (src->i_ino == dest->i_ino)
+ goto commit_flags;
+
+ if (!xfs_is_reflink_inode(dest)) {
+ trace_xfs_reflink_set_inode_flag(dest);
+ xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
+ dest->i_diflags2 |= XFS_DIFLAG2_REFLINK;
+ xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
+ xfs_ifork_init_cow(dest);
+ } else
+ xfs_iunlock(dest, XFS_ILOCK_EXCL);
+
+commit_flags:
+ error = xfs_trans_commit(tp);
+ if (error)
+ goto out_error;
+ return error;
+
+out_error:
+ trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
+ return error;
+}
+
+/*
+ * Update destination inode size & cowextsize hint, if necessary.
+ */
+int
+xfs_reflink_update_dest(
+ struct xfs_inode *dest,
+ xfs_off_t newlen,
+ xfs_extlen_t cowextsize,
+ unsigned int remap_flags)
+{
+ struct xfs_mount *mp = dest->i_mount;
+ struct xfs_trans *tp;
+ int error;
+
+ if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
+ return 0;
+
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
+ if (error)
+ goto out_error;
+
+ xfs_ilock(dest, XFS_ILOCK_EXCL);
+ xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
+
+ if (newlen > i_size_read(VFS_I(dest))) {
+ trace_xfs_reflink_update_inode_size(dest, newlen);
+ i_size_write(VFS_I(dest), newlen);
+ dest->i_disk_size = newlen;
+ }
+
+ if (cowextsize) {
+ dest->i_cowextsize = cowextsize;
+ dest->i_diflags2 |= XFS_DIFLAG2_COWEXTSIZE;
+ }
+
+ xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
+
+ error = xfs_trans_commit(tp);
+ if (error)
+ goto out_error;
+ return error;
+
+out_error:
+ trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
+ return error;
+}
+
+/*
+ * Do we have enough reserve in this AG to handle a reflink? The refcount
+ * btree already reserved all the space it needs, but the rmap btree can grow
+ * infinitely, so we won't allow more reflinks when the AG is down to the
+ * btree reserves.
+ */
+static int
+xfs_reflink_ag_has_free_space(
+ struct xfs_mount *mp,
+ xfs_agnumber_t agno)
+{
+ struct xfs_perag *pag;
+ int error = 0;
+
+ if (!xfs_has_rmapbt(mp))
+ return 0;
+
+ pag = xfs_perag_get(mp, agno);
+ if (xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) ||
+ xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
+ error = -ENOSPC;
+ xfs_perag_put(pag);
+ return error;
+}
+
+/*
+ * Remap the given extent into the file. The dmap blockcount will be set to
+ * the number of blocks that were actually remapped.
+ */
+STATIC int
+xfs_reflink_remap_extent(
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *dmap,
+ xfs_off_t new_isize)
+{
+ struct xfs_bmbt_irec smap;
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ xfs_off_t newlen;
+ int64_t qdelta = 0;
+ unsigned int resblks;
+ bool quota_reserved = true;
+ bool smap_real;
+ bool dmap_written = xfs_bmap_is_written_extent(dmap);
+ int iext_delta = 0;
+ int nimaps;
+ int error;
+
+ /*
+ * Start a rolling transaction to switch the mappings.
+ *
+ * Adding a written extent to the extent map can cause a bmbt split,
+ * and removing a mapped extent from the extent can cause a bmbt split.
+ * The two operations cannot both cause a split since they operate on
+ * the same index in the bmap btree, so we only need a reservation for
+ * one bmbt split if either thing is happening. However, we haven't
+ * locked the inode yet, so we reserve assuming this is the case.
+ *
+ * The first allocation call tries to reserve enough space to handle
+ * mapping dmap into a sparse part of the file plus the bmbt split. We
+ * haven't locked the inode or read the existing mapping yet, so we do
+ * not know for sure that we need the space. This should succeed most
+ * of the time.
+ *
+ * If the first attempt fails, try again but reserving only enough
+ * space to handle a bmbt split. This is the hard minimum requirement,
+ * and we revisit quota reservations later when we know more about what
+ * we're remapping.
+ */
+ resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
+ error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
+ resblks + dmap->br_blockcount, 0, false, &tp);
+ if (error == -EDQUOT || error == -ENOSPC) {
+ quota_reserved = false;
+ error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
+ resblks, 0, false, &tp);
+ }
+ if (error)
+ goto out;
+
+ /*
+ * Read what's currently mapped in the destination file into smap.
+ * If smap isn't a hole, we will have to remove it before we can add
+ * dmap to the destination file.
+ */
+ nimaps = 1;
+ error = xfs_bmapi_read(ip, dmap->br_startoff, dmap->br_blockcount,
+ &smap, &nimaps, 0);
+ if (error)
+ goto out_cancel;
+ ASSERT(nimaps == 1 && smap.br_startoff == dmap->br_startoff);
+ smap_real = xfs_bmap_is_real_extent(&smap);
+
+ /*
+ * We can only remap as many blocks as the smaller of the two extent
+ * maps, because we can only remap one extent at a time.
+ */
+ dmap->br_blockcount = min(dmap->br_blockcount, smap.br_blockcount);
+ ASSERT(dmap->br_blockcount == smap.br_blockcount);
+
+ trace_xfs_reflink_remap_extent_dest(ip, &smap);
+
+ /*
+ * Two extents mapped to the same physical block must not have
+ * different states; that's filesystem corruption. Move on to the next
+ * extent if they're both holes or both the same physical extent.
+ */
+ if (dmap->br_startblock == smap.br_startblock) {
+ if (dmap->br_state != smap.br_state)
+ error = -EFSCORRUPTED;
+ goto out_cancel;
+ }
+
+ /* If both extents are unwritten, leave them alone. */
+ if (dmap->br_state == XFS_EXT_UNWRITTEN &&
+ smap.br_state == XFS_EXT_UNWRITTEN)
+ goto out_cancel;
+
+ /* No reflinking if the AG of the dest mapping is low on space. */
+ if (dmap_written) {
+ error = xfs_reflink_ag_has_free_space(mp,
+ XFS_FSB_TO_AGNO(mp, dmap->br_startblock));
+ if (error)
+ goto out_cancel;
+ }
+
+ /*
+ * Increase quota reservation if we think the quota block counter for
+ * this file could increase.
+ *
+ * If we are mapping a written extent into the file, we need to have
+ * enough quota block count reservation to handle the blocks in that
+ * extent. We log only the delta to the quota block counts, so if the
+ * extent we're unmapping also has blocks allocated to it, we don't
+ * need a quota reservation for the extent itself.
+ *
+ * Note that if we're replacing a delalloc reservation with a written
+ * extent, we have to take the full quota reservation because removing
+ * the delalloc reservation gives the block count back to the quota
+ * count. This is suboptimal, but the VFS flushed the dest range
+ * before we started. That should have removed all the delalloc
+ * reservations, but we code defensively.
+ *
+ * xfs_trans_alloc_inode above already tried to grab an even larger
+ * quota reservation, and kicked off a blockgc scan if it couldn't.
+ * If we can't get a potentially smaller quota reservation now, we're
+ * done.
+ */
+ if (!quota_reserved && !smap_real && dmap_written) {
+ error = xfs_trans_reserve_quota_nblks(tp, ip,
+ dmap->br_blockcount, 0, false);
+ if (error)
+ goto out_cancel;
+ }
+
+ if (smap_real)
+ ++iext_delta;
+
+ if (dmap_written)
+ ++iext_delta;
+
+ error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, iext_delta);
+ if (error == -EFBIG)
+ error = xfs_iext_count_upgrade(tp, ip, iext_delta);
+ if (error)
+ goto out_cancel;
+
+ if (smap_real) {
+ /*
+ * If the extent we're unmapping is backed by storage (written
+ * or not), unmap the extent and drop its refcount.
+ */
+ xfs_bmap_unmap_extent(tp, ip, &smap);
+ xfs_refcount_decrease_extent(tp, &smap);
+ qdelta -= smap.br_blockcount;
+ } else if (smap.br_startblock == DELAYSTARTBLOCK) {
+ int done;
+
+ /*
+ * If the extent we're unmapping is a delalloc reservation,
+ * we can use the regular bunmapi function to release the
+ * incore state. Dropping the delalloc reservation takes care
+ * of the quota reservation for us.
+ */
+ error = xfs_bunmapi(NULL, ip, smap.br_startoff,
+ smap.br_blockcount, 0, 1, &done);
+ if (error)
+ goto out_cancel;
+ ASSERT(done);
+ }
+
+ /*
+ * If the extent we're sharing is backed by written storage, increase
+ * its refcount and map it into the file.
+ */
+ if (dmap_written) {
+ xfs_refcount_increase_extent(tp, dmap);
+ xfs_bmap_map_extent(tp, ip, dmap);
+ qdelta += dmap->br_blockcount;
+ }
+
+ xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, qdelta);
+
+ /* Update dest isize if needed. */
+ newlen = XFS_FSB_TO_B(mp, dmap->br_startoff + dmap->br_blockcount);
+ newlen = min_t(xfs_off_t, newlen, new_isize);
+ if (newlen > i_size_read(VFS_I(ip))) {
+ trace_xfs_reflink_update_inode_size(ip, newlen);
+ i_size_write(VFS_I(ip), newlen);
+ ip->i_disk_size = newlen;
+ xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+ }
+
+ /* Commit everything and unlock. */
+ error = xfs_trans_commit(tp);
+ goto out_unlock;
+
+out_cancel:
+ xfs_trans_cancel(tp);
+out_unlock:
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+out:
+ if (error)
+ trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
+ return error;
+}
+
+/* Remap a range of one file to the other. */
+int
+xfs_reflink_remap_blocks(
+ struct xfs_inode *src,
+ loff_t pos_in,
+ struct xfs_inode *dest,
+ loff_t pos_out,
+ loff_t remap_len,
+ loff_t *remapped)
+{
+ struct xfs_bmbt_irec imap;
+ struct xfs_mount *mp = src->i_mount;
+ xfs_fileoff_t srcoff = XFS_B_TO_FSBT(mp, pos_in);
+ xfs_fileoff_t destoff = XFS_B_TO_FSBT(mp, pos_out);
+ xfs_filblks_t len;
+ xfs_filblks_t remapped_len = 0;
+ xfs_off_t new_isize = pos_out + remap_len;
+ int nimaps;
+ int error = 0;
+
+ len = min_t(xfs_filblks_t, XFS_B_TO_FSB(mp, remap_len),
+ XFS_MAX_FILEOFF);
+
+ trace_xfs_reflink_remap_blocks(src, srcoff, len, dest, destoff);
+
+ while (len > 0) {
+ unsigned int lock_mode;
+
+ /* Read extent from the source file */
+ nimaps = 1;
+ lock_mode = xfs_ilock_data_map_shared(src);
+ error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
+ xfs_iunlock(src, lock_mode);
+ if (error)
+ break;
+ /*
+ * The caller supposedly flushed all dirty pages in the source
+ * file range, which means that writeback should have allocated
+ * or deleted all delalloc reservations in that range. If we
+ * find one, that's a good sign that something is seriously
+ * wrong here.
+ */
+ ASSERT(nimaps == 1 && imap.br_startoff == srcoff);
+ if (imap.br_startblock == DELAYSTARTBLOCK) {
+ ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
+ error = -EFSCORRUPTED;
+ break;
+ }
+
+ trace_xfs_reflink_remap_extent_src(src, &imap);
+
+ /* Remap into the destination file at the given offset. */
+ imap.br_startoff = destoff;
+ error = xfs_reflink_remap_extent(dest, &imap, new_isize);
+ if (error)
+ break;
+
+ if (fatal_signal_pending(current)) {
+ error = -EINTR;
+ break;
+ }
+
+ /* Advance drange/srange */
+ srcoff += imap.br_blockcount;
+ destoff += imap.br_blockcount;
+ len -= imap.br_blockcount;
+ remapped_len += imap.br_blockcount;
+ }
+
+ if (error)
+ trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
+ *remapped = min_t(loff_t, remap_len,
+ XFS_FSB_TO_B(src->i_mount, remapped_len));
+ return error;
+}
+
+/*
+ * If we're reflinking to a point past the destination file's EOF, we must
+ * zero any speculative post-EOF preallocations that sit between the old EOF
+ * and the destination file offset.
+ */
+static int
+xfs_reflink_zero_posteof(
+ struct xfs_inode *ip,
+ loff_t pos)
+{
+ loff_t isize = i_size_read(VFS_I(ip));
+
+ if (pos <= isize)
+ return 0;
+
+ trace_xfs_zero_eof(ip, isize, pos - isize);
+ return xfs_zero_range(ip, isize, pos - isize, NULL);
+}
+
+/*
+ * Prepare two files for range cloning. Upon a successful return both inodes
+ * will have the iolock and mmaplock held, the page cache of the out file will
+ * be truncated, and any leases on the out file will have been broken. This
+ * function borrows heavily from xfs_file_aio_write_checks.
+ *
+ * The VFS allows partial EOF blocks to "match" for dedupe even though it hasn't
+ * checked that the bytes beyond EOF physically match. Hence we cannot use the
+ * EOF block in the source dedupe range because it's not a complete block match,
+ * hence can introduce a corruption into the file that has it's block replaced.
+ *
+ * In similar fashion, the VFS file cloning also allows partial EOF blocks to be
+ * "block aligned" for the purposes of cloning entire files. However, if the
+ * source file range includes the EOF block and it lands within the existing EOF
+ * of the destination file, then we can expose stale data from beyond the source
+ * file EOF in the destination file.
+ *
+ * XFS doesn't support partial block sharing, so in both cases we have check
+ * these cases ourselves. For dedupe, we can simply round the length to dedupe
+ * down to the previous whole block and ignore the partial EOF block. While this
+ * means we can't dedupe the last block of a file, this is an acceptible
+ * tradeoff for simplicity on implementation.
+ *
+ * For cloning, we want to share the partial EOF block if it is also the new EOF
+ * block of the destination file. If the partial EOF block lies inside the
+ * existing destination EOF, then we have to abort the clone to avoid exposing
+ * stale data in the destination file. Hence we reject these clone attempts with
+ * -EINVAL in this case.
+ */
+int
+xfs_reflink_remap_prep(
+ struct file *file_in,
+ loff_t pos_in,
+ struct file *file_out,
+ loff_t pos_out,
+ loff_t *len,
+ unsigned int remap_flags)
+{
+ struct inode *inode_in = file_inode(file_in);
+ struct xfs_inode *src = XFS_I(inode_in);
+ struct inode *inode_out = file_inode(file_out);
+ struct xfs_inode *dest = XFS_I(inode_out);
+ int ret;
+
+ /* Lock both files against IO */
+ ret = xfs_ilock2_io_mmap(src, dest);
+ if (ret)
+ return ret;
+
+ /* Check file eligibility and prepare for block sharing. */
+ ret = -EINVAL;
+ /* Don't reflink realtime inodes */
+ if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
+ goto out_unlock;
+
+ /* Don't share DAX file data with non-DAX file. */
+ if (IS_DAX(inode_in) != IS_DAX(inode_out))
+ goto out_unlock;
+
+ if (!IS_DAX(inode_in))
+ ret = generic_remap_file_range_prep(file_in, pos_in, file_out,
+ pos_out, len, remap_flags);
+ else
+ ret = dax_remap_file_range_prep(file_in, pos_in, file_out,
+ pos_out, len, remap_flags, &xfs_read_iomap_ops);
+ if (ret || *len == 0)
+ goto out_unlock;
+
+ /* Attach dquots to dest inode before changing block map */
+ ret = xfs_qm_dqattach(dest);
+ if (ret)
+ goto out_unlock;
+
+ /*
+ * Zero existing post-eof speculative preallocations in the destination
+ * file.
+ */
+ ret = xfs_reflink_zero_posteof(dest, pos_out);
+ if (ret)
+ goto out_unlock;
+
+ /* Set flags and remap blocks. */
+ ret = xfs_reflink_set_inode_flag(src, dest);
+ if (ret)
+ goto out_unlock;
+
+ /*
+ * If pos_out > EOF, we may have dirtied blocks between EOF and
+ * pos_out. In that case, we need to extend the flush and unmap to cover
+ * from EOF to the end of the copy length.
+ */
+ if (pos_out > XFS_ISIZE(dest)) {
+ loff_t flen = *len + (pos_out - XFS_ISIZE(dest));
+ ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen);
+ } else {
+ ret = xfs_flush_unmap_range(dest, pos_out, *len);
+ }
+ if (ret)
+ goto out_unlock;
+
+ return 0;
+out_unlock:
+ xfs_iunlock2_io_mmap(src, dest);
+ return ret;
+}
+
+/* Does this inode need the reflink flag? */
+int
+xfs_reflink_inode_has_shared_extents(
+ struct xfs_trans *tp,
+ struct xfs_inode *ip,
+ bool *has_shared)
+{
+ struct xfs_bmbt_irec got;
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_ifork *ifp;
+ struct xfs_iext_cursor icur;
+ bool found;
+ int error;
+
+ ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
+ error = xfs_iread_extents(tp, ip, XFS_DATA_FORK);
+ if (error)
+ return error;
+
+ *has_shared = false;
+ found = xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got);
+ while (found) {
+ struct xfs_perag *pag;
+ xfs_agblock_t agbno;
+ xfs_extlen_t aglen;
+ xfs_agblock_t rbno;
+ xfs_extlen_t rlen;
+
+ if (isnullstartblock(got.br_startblock) ||
+ got.br_state != XFS_EXT_NORM)
+ goto next;
+
+ pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, got.br_startblock));
+ agbno = XFS_FSB_TO_AGBNO(mp, got.br_startblock);
+ aglen = got.br_blockcount;
+ error = xfs_reflink_find_shared(pag, tp, agbno, aglen,
+ &rbno, &rlen, false);
+ xfs_perag_put(pag);
+ if (error)
+ return error;
+
+ /* Is there still a shared block here? */
+ if (rbno != NULLAGBLOCK) {
+ *has_shared = true;
+ return 0;
+ }
+next:
+ found = xfs_iext_next_extent(ifp, &icur, &got);
+ }
+
+ return 0;
+}
+
+/*
+ * Clear the inode reflink flag if there are no shared extents.
+ *
+ * The caller is responsible for joining the inode to the transaction passed in.
+ * The inode will be joined to the transaction that is returned to the caller.
+ */
+int
+xfs_reflink_clear_inode_flag(
+ struct xfs_inode *ip,
+ struct xfs_trans **tpp)
+{
+ bool needs_flag;
+ int error = 0;
+
+ ASSERT(xfs_is_reflink_inode(ip));
+
+ error = xfs_reflink_inode_has_shared_extents(*tpp, ip, &needs_flag);
+ if (error || needs_flag)
+ return error;
+
+ /*
+ * We didn't find any shared blocks so turn off the reflink flag.
+ * First, get rid of any leftover CoW mappings.
+ */
+ error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, XFS_MAX_FILEOFF,
+ true);
+ if (error)
+ return error;
+
+ /* Clear the inode flag. */
+ trace_xfs_reflink_unset_inode_flag(ip);
+ ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
+ xfs_inode_clear_cowblocks_tag(ip);
+ xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
+
+ return error;
+}
+
+/*
+ * Clear the inode reflink flag if there are no shared extents and the size
+ * hasn't changed.
+ */
+STATIC int
+xfs_reflink_try_clear_inode_flag(
+ struct xfs_inode *ip)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ int error = 0;
+
+ /* Start a rolling transaction to remove the mappings */
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
+ if (error)
+ return error;
+
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ xfs_trans_ijoin(tp, ip, 0);
+
+ error = xfs_reflink_clear_inode_flag(ip, &tp);
+ if (error)
+ goto cancel;
+
+ error = xfs_trans_commit(tp);
+ if (error)
+ goto out;
+
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return 0;
+cancel:
+ xfs_trans_cancel(tp);
+out:
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+}
+
+/*
+ * Pre-COW all shared blocks within a given byte range of a file and turn off
+ * the reflink flag if we unshare all of the file's blocks.
+ */
+int
+xfs_reflink_unshare(
+ struct xfs_inode *ip,
+ xfs_off_t offset,
+ xfs_off_t len)
+{
+ struct inode *inode = VFS_I(ip);
+ int error;
+
+ if (!xfs_is_reflink_inode(ip))
+ return 0;
+
+ trace_xfs_reflink_unshare(ip, offset, len);
+
+ inode_dio_wait(inode);
+
+ if (IS_DAX(inode))
+ error = dax_file_unshare(inode, offset, len,
+ &xfs_dax_write_iomap_ops);
+ else
+ error = iomap_file_unshare(inode, offset, len,
+ &xfs_buffered_write_iomap_ops);
+ if (error)
+ goto out;
+
+ error = filemap_write_and_wait_range(inode->i_mapping, offset,
+ offset + len - 1);
+ if (error)
+ goto out;
+
+ /* Turn off the reflink flag if possible. */
+ error = xfs_reflink_try_clear_inode_flag(ip);
+ if (error)
+ goto out;
+ return 0;
+
+out:
+ trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
+ return error;
+}