From d0641780940a9842cbf62114bc8422012c7d88c4 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Wed, 2 May 2018 12:54:53 -0700 Subject: [PATCH] xfs: simplify xfs_file_iomap_begin() logic 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 Reviewed-by: Carlos Maiolino Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- 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; -- 2.11.0