From: Dave Chinner <dchinner@xxxxxxxxxx>
The current logic that determines whether allocation should be done
has grown somewhat spaghetti like with the addition of IOMAP_NOWAIT
functionality. Separate out each of the different cases into single,
obvious checks to get rid most of the nested IOMAP_NOWAIT checks
in the allocation logic.
Signed-Off-By: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_iomap.c | 82 ++++++++++++++++++++++++++--------------------
1 file changed, 46 insertions(+), 36 deletions(-)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 046469fcc1b8..16565da67bb6 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1040,6 +1040,10 @@ xfs_file_iomap_begin(
goto out_unlock;
}
+ /* Non-modifying mapping requested, so we are done */
+ if (!(flags & (IOMAP_WRITE | IOMAP_ZERO)))
+ goto out_found;
+
if (xfs_is_reflink_inode(ip) &&
((flags & IOMAP_WRITE) ||
((flags & IOMAP_ZERO) && needs_cow_for_zeroing(&imap, nimaps)))) {
@@ -1068,46 +1072,45 @@ xfs_file_iomap_begin(
length = XFS_FSB_TO_B(mp, end_fsb) - offset;
}
- if ((flags & IOMAP_WRITE) && imap_needs_alloc(inode, &imap, nimaps)) {
- /*
- * If nowait is set bail since we are going to make
- * allocations.
- */
- if (flags & IOMAP_NOWAIT) {
- error = -EAGAIN;
- goto out_unlock;
- }
- /*
- * We cap the maximum length we map here to MAX_WRITEBACK_PAGES
- * pages to keep the chunks of work done where somewhat symmetric
- * with the work writeback does. This is a completely arbitrary
- * number pulled out of thin air as a best guess for initial
- * testing.
- *
- * Note that the values needs to be less than 32-bits wide until
- * the lower level functions are updated.
- */
- length = min_t(loff_t, length, 1024 * PAGE_SIZE);
- /*
- * xfs_iomap_write_direct() expects the shared lock. It
- * is unlocked on return.
- */
- if (lockmode == XFS_ILOCK_EXCL)
- xfs_ilock_demote(ip, lockmode);
- error = xfs_iomap_write_direct(ip, offset, length, &imap,
- nimaps);
- if (error)
- return error;
+ /* Don't need to allocate over holes when doing zeroing operations. */
+ if (flags & IOMAP_ZERO)
+ goto out_found;
- iomap->flags = IOMAP_F_NEW;
- trace_xfs_iomap_alloc(ip, offset, length, 0, &imap);
- } else {
- ASSERT(nimaps);
+ if (!imap_needs_alloc(inode, &imap, nimaps))
+ goto out_found;
- xfs_iunlock(ip, lockmode);
- trace_xfs_iomap_found(ip, offset, length, 0, &imap);
+ /* If nowait is set bail since we are going to make allocations. */
+ if (flags & IOMAP_NOWAIT) {
+ error = -EAGAIN;
+ goto out_unlock;
}
+ /*
+ * We cap the maximum length we map to a sane size to keep the chunks
+ * of work done where somewhat symmetric with the work writeback does.
+ * This is a completely arbitrary number pulled out of thin air as a
+ * best guess for initial testing.
+ *
+ * Note that the values needs to be less than 32-bits wide until the
+ * lower level functions are updated.
+ */
+ length = min_t(loff_t, length, 1024 * PAGE_SIZE);
+
+ /*
+ * xfs_iomap_write_direct() expects the shared lock. It is unlocked on
+ * return.
+ */
+ if (lockmode == XFS_ILOCK_EXCL)
+ xfs_ilock_demote(ip, lockmode);
+ error = xfs_iomap_write_direct(ip, offset, length, &imap,
+ nimaps);
+ if (error)
+ return error;
+
+ iomap->flags = IOMAP_F_NEW;
+ trace_xfs_iomap_alloc(ip, offset, length, 0, &imap);
+
+out_finish:
if (xfs_ipincount(ip) && (ip->i_itemp->ili_fsync_fields
& ~XFS_ILOG_TIMESTAMP))
iomap->flags |= IOMAP_F_DIRTY;
@@ -1117,6 +1120,13 @@ xfs_file_iomap_begin(
if (shared)
iomap->flags |= IOMAP_F_SHARED;
return 0;
+
+out_found:
+ ASSERT(nimaps);
+ xfs_iunlock(ip, lockmode);
+ trace_xfs_iomap_found(ip, offset, length, 0, &imap);
+ goto out_finish;
+
out_unlock:
xfs_iunlock(ip, lockmode);
return error;
--
2.17.0
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