COW fork reservation (delayed allocation) is implemented in
xfs_reflink_reserve_cow() and is generally based on the traditional data
fork delalloc logic in xfs_file_iomap_begin_delay(). In preparation for
further changes to implement more aggressive COW fork preallocation,
refactor the COW reservation code to reuse xfs_file_iomap_begin_delay()
for data fork allocation as well as COW fork reservation. This patch
does not change behavior.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
---
fs/xfs/xfs_iomap.c | 74 ++++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 55 insertions(+), 19 deletions(-)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 0dec431c..9072bdb 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -527,9 +527,8 @@ xfs_iomap_prealloc_size(
* inode data and COW forks. If an existing data extent is shared, determine
* whether COW fork reservation is necessary.
*
- * The 'found' parameter indicates whether a writable mapping was found. If the
- * mapping is shared, a COW reservation is performed for the corresponding
- * range.
+ * The 'found' parameter indicates whether a writable mapping was found. If a
+ * shared mapping exists, found is set only if COW reservation exists as well.
*/
static int
xfs_iomap_search_extents(
@@ -540,12 +539,14 @@ xfs_iomap_search_extents(
int *eof,
int *idx,
struct xfs_bmbt_irec *got,
+ bool *shared,
bool *found) /* found usable extent */
{
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
int error = 0;
+ bool trimmed;
- *found = false;
+ *shared = *found = false;
/*
* Look up a preexisting extent directly into imap. Set got for the
@@ -556,17 +557,37 @@ xfs_iomap_search_extents(
*got = *imap;
return 0;
}
+ if (!xfs_is_reflink_inode(ip)) {
+ *found = true;
+ return 0;
+ }
- if (xfs_is_reflink_inode(ip)) {
- bool shared;
-
- xfs_trim_extent(imap, offset_fsb, end_fsb - offset_fsb);
- error = xfs_reflink_reserve_cow(ip, imap, &shared);
- if (error)
- return error;
+ /*
+ * Found a data extent but we don't know if it is shared. If an extent
+ * exists in the cow fork, assume that it is. Use got for this lookup as
+ * imap must retain the data mapping.
+ */
+ xfs_trim_extent(imap, offset_fsb, end_fsb - offset_fsb);
+ ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+ *eof = !xfs_iext_lookup_extent(ip, ifp, offset_fsb, idx, got);
+ if (!*eof && got->br_startoff <= imap->br_startoff) {
+ trace_xfs_reflink_cow_found(ip, got);
+ xfs_trim_extent(imap, got->br_startoff, got->br_blockcount);
+ *found = true;
+ return 0;
}
- *found = true;
+ /*
+ * There is no existing cow fork extent. We have to explicitly check if
+ * the data extent is shared to determine whether COW fork reservation
+ * is required to map the data extent. Trim the mapping to the next
+ * (un)shared boundary at the same time.
+ */
+ error = xfs_reflink_trim_around_shared(ip, imap, shared, &trimmed);
+ if (error)
+ return error;
+ if (!*shared)
+ *found = true;
return error;
}
@@ -587,11 +608,13 @@ xfs_file_iomap_begin_delay(
xfs_fileoff_t maxbytes_fsb =
XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
int error = 0, eof = 0;
+ int fork = XFS_DATA_FORK;
struct xfs_bmbt_irec imap;
struct xfs_bmbt_irec got;
xfs_extnum_t idx;
xfs_fsblock_t prealloc_blocks = 0;
bool found;
+ bool shared;
ASSERT(!XFS_IS_REALTIME_INODE(ip));
ASSERT(!xfs_get_extsz_hint(ip));
@@ -620,16 +643,20 @@ xfs_file_iomap_begin_delay(
/*
* Search for preexisting extents. If an existing data extent is shared,
- * this will perform COW fork reservation.
+ * switch to the COW fork for COW reservation.
*/
error = xfs_iomap_search_extents(ip, offset_fsb, end_fsb, &imap, &eof,
- &idx, &got, &found);
+ &idx, &got, &shared, &found);
if (error)
goto out_unlock;
if (found) {
trace_xfs_iomap_found(ip, offset, count, 0, &imap);
goto done;
}
+ if (shared) {
+ end_fsb = imap.br_startoff + imap.br_blockcount;
+ fork = XFS_COW_FORK;
+ }
error = xfs_qm_dqattach_locked(ip, 0);
if (error)
@@ -645,9 +672,10 @@ xfs_file_iomap_begin_delay(
* the lower level functions are updated.
*/
count = min_t(loff_t, count, 1024 * PAGE_SIZE);
- end_fsb = min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
+ end_fsb = min(end_fsb, XFS_B_TO_FSB(mp, offset + count));
+ xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
- if (eof) {
+ if (eof && fork == XFS_DATA_FORK) {
prealloc_blocks = xfs_iomap_prealloc_size(ip, offset, count, idx);
if (prealloc_blocks) {
xfs_extlen_t align;
@@ -669,7 +697,7 @@ xfs_file_iomap_begin_delay(
}
retry:
- error = xfs_bmapi_reserve_delalloc(ip, XFS_DATA_FORK, offset_fsb,
+ error = xfs_bmapi_reserve_delalloc(ip, fork, offset_fsb,
end_fsb - offset_fsb, prealloc_blocks, &got, &idx, eof);
switch (error) {
case 0:
@@ -687,8 +715,16 @@ xfs_file_iomap_begin_delay(
goto out_unlock;
}
- trace_xfs_iomap_alloc(ip, offset, count, 0, &got);
- imap = got;
+ /*
+ * For the data fork, the iomap mapping is simply the extent that was
+ * returned from the delalloc request. Otherwise, use imap as it refers
+ * to the data fork but is trimmed according to the shared state.
+ */
+ if (fork == XFS_DATA_FORK) {
+ trace_xfs_iomap_alloc(ip, offset, count, 0, &got);
+ imap = got;
+ } else
+ trace_xfs_reflink_cow_alloc(ip, &got);
done:
if (isnullstartblock(imap.br_startblock))
imap.br_startblock = DELAYSTARTBLOCK;
--
2.7.4
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