@@ -481,6 +481,12 @@ xfs_submit_ioend(
struct xfs_ioend *ioend,
int status)
{
+ /* Convert CoW extents to regular */
+ if (!status && ioend->io_type == XFS_IO_COW) {
+ status = xfs_reflink_convert_cow(XFS_I(ioend->io_inode),
+ ioend->io_offset, ioend->io_size);
+ }
+
/* Reserve log space if we might write beyond the on-disk inode size. */
if (!status &&
ioend->io_type != XFS_IO_UNWRITTEN &&
@@ -685,7 +685,7 @@ xfs_iomap_write_allocate(
int nres;
if (whichfork == XFS_COW_FORK)
- flags |= XFS_BMAPI_COWFORK;
+ flags |= XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC;
/*
* Make sure that the dquots are there.
@@ -82,11 +82,22 @@
* 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 real mappings by allocating
- * blocks and replacing the delalloc mapping with real ones. A delalloc
- * mapping can be replaced by several real ones if the free space is
- * fragmented.
+ * 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
@@ -101,13 +112,29 @@
* 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.
+ * 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
@@ -296,6 +323,89 @@ xfs_reflink_reserve_cow(
return 0;
}
+/* Convert part of an unwritten CoW extent to a real one. */
+STATIC int
+__xfs_reflink_convert_cow(
+ struct xfs_trans *tp,
+ struct xfs_inode *ip,
+ struct xfs_bmbt_irec *imap,
+ xfs_fileoff_t offset_fsb,
+ xfs_filblks_t count_fsb,
+ struct xfs_defer_ops *dfops)
+{
+ struct xfs_bmbt_irec irec = *imap;
+ xfs_fsblock_t first_block;
+ int nimaps = 1;
+
+ xfs_trim_extent(&irec, offset_fsb, count_fsb);
+ trace_xfs_reflink_convert_cow(ip, &irec);
+ if (irec.br_blockcount == 0)
+ return 0;
+ return xfs_bmapi_write(tp, ip, irec.br_startoff, irec.br_blockcount,
+ XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT, &first_block,
+ 0, &irec, &nimaps, dfops);
+}
+
+/* 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_bmbt_irec got;
+ struct xfs_defer_ops dfops;
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+ struct xfs_trans *tp;
+ xfs_fsblock_t first_block;
+ xfs_fileoff_t offset_fsb;
+ xfs_fileoff_t end_fsb;
+ xfs_extnum_t idx;
+ bool found;
+ int error;
+
+ offset_fsb = XFS_B_TO_FSBT(mp, offset);
+ end_fsb = XFS_B_TO_FSB(mp, offset + count);
+
+ /* Grab transaction. */
+ 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);
+ xfs_defer_init(&dfops, &first_block);
+
+ /* Convert all the extents to real from unwritten. */
+ for (found = xfs_iext_lookup_extent(ip, ifp, offset_fsb, &idx, &got);
+ found && got.br_startoff < end_fsb;
+ found = xfs_iext_get_extent(ifp, ++idx, &got)) {
+ if (got.br_state == XFS_EXT_NORM)
+ continue;
+ error = __xfs_reflink_convert_cow(tp, ip, &got, offset_fsb,
+ end_fsb - offset_fsb, &dfops);
+ if (error)
+ goto err;
+ }
+
+ /* Finish up. */
+ error = xfs_defer_finish(&tp, &dfops, NULL);
+ if (error)
+ goto out_trans_cancel;
+
+ error = xfs_trans_commit(tp);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+
+err:
+ xfs_defer_cancel(&dfops);
+out_trans_cancel:
+ xfs_trans_cancel(tp);
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+}
+
/* Allocate all CoW reservations covering a range of blocks in a file. */
static int
__xfs_reflink_allocate_cow(
@@ -328,6 +438,7 @@ __xfs_reflink_allocate_cow(
goto out_unlock;
ASSERT(nimaps == 1);
+ /* Make sure there's a CoW reservation for it. */
error = xfs_reflink_reserve_cow(ip, &imap, &shared);
if (error)
goto out_trans_cancel;
@@ -337,14 +448,16 @@ __xfs_reflink_allocate_cow(
goto out_trans_cancel;
}
+ /* Allocate the entire reservation as unwritten blocks. */
xfs_trans_ijoin(tp, ip, 0);
error = xfs_bmapi_write(tp, ip, imap.br_startoff, imap.br_blockcount,
- XFS_BMAPI_COWFORK, &first_block,
+ XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, &first_block,
XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK),
&imap, &nimaps, &dfops);
if (error)
goto out_trans_cancel;
+ /* Finish up. */
error = xfs_defer_finish(&tp, &dfops, NULL);
if (error)
goto out_trans_cancel;
@@ -389,10 +502,13 @@ xfs_reflink_allocate_cow_range(
if (error) {
trace_xfs_reflink_allocate_cow_range_error(ip, error,
_RET_IP_);
- break;
+ goto out;
}
}
+ /* Convert the CoW extents to regular. */
+ error = xfs_reflink_convert_cow(ip, offset, count);
+out:
return error;
}
@@ -641,6 +757,16 @@ xfs_reflink_end_cow(
ASSERT(!isnullstartblock(got.br_startblock));
+ /*
+ * Don't remap unwritten extents; these are
+ * speculatively preallocated CoW extents that have been
+ * allocated but have not yet been involved in a write.
+ */
+ if (got.br_state == XFS_EXT_UNWRITTEN) {
+ idx--;
+ goto next_extent;
+ }
+
/* Unmap the old blocks in the data fork. */
xfs_defer_init(&dfops, &firstfsb);
rlen = del.br_blockcount;
@@ -30,6 +30,8 @@ extern int xfs_reflink_reserve_cow(struct xfs_inode *ip,
struct xfs_bmbt_irec *imap, bool *shared);
extern int xfs_reflink_allocate_cow_range(struct xfs_inode *ip,
xfs_off_t offset, xfs_off_t count);
+extern int xfs_reflink_convert_cow(struct xfs_inode *ip, xfs_off_t offset,
+ xfs_off_t count);
extern bool xfs_reflink_find_cow_mapping(struct xfs_inode *ip, xfs_off_t offset,
struct xfs_bmbt_irec *imap);
extern void xfs_reflink_trim_irec_to_next_cow(struct xfs_inode *ip,
@@ -3089,6 +3089,7 @@ DECLARE_EVENT_CLASS(xfs_inode_irec_class,
__field(xfs_fileoff_t, lblk)
__field(xfs_extlen_t, len)
__field(xfs_fsblock_t, pblk)
+ __field(int, state)
),
TP_fast_assign(
__entry->dev = VFS_I(ip)->i_sb->s_dev;
@@ -3096,13 +3097,15 @@ DECLARE_EVENT_CLASS(xfs_inode_irec_class,
__entry->lblk = irec->br_startoff;
__entry->len = irec->br_blockcount;
__entry->pblk = irec->br_startblock;
+ __entry->state = irec->br_state;
),
- TP_printk("dev %d:%d ino 0x%llx lblk 0x%llx len 0x%x pblk %llu",
+ TP_printk("dev %d:%d ino 0x%llx lblk 0x%llx len 0x%x pblk %llu st %d",
MAJOR(__entry->dev), MINOR(__entry->dev),
__entry->ino,
__entry->lblk,
__entry->len,
- __entry->pblk)
+ __entry->pblk,
+ __entry->state)
);
#define DEFINE_INODE_IREC_EVENT(name) \
DEFINE_EVENT(xfs_inode_irec_class, name, \
@@ -3242,6 +3245,7 @@ DEFINE_INODE_IREC_EVENT(xfs_reflink_trim_around_shared);
DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_alloc);
DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_found);
DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_enospc);
+DEFINE_INODE_IREC_EVENT(xfs_reflink_convert_cow);
DEFINE_RW_EVENT(xfs_reflink_reserve_cow);
DEFINE_RW_EVENT(xfs_reflink_allocate_cow_range);