ore: Only IO one group at a time (API change)

Usually a single IO is confined to one group of devices
(group_width) and at the boundary of a raid group it can
spill into a second group. Current code would allocate a
full device_table size array at each io_state so it can
comply to requests that span two groups. Needless to say
that is very wasteful, specially when device_table count
can get very large (hundreds even thousands), while a
group_width is usually 8 or 10.

* Change ore API to trim on IO that spans two raid groups.
  The user passes offset+length to ore_get_rw_state, the
  ore might trim on that length if spanning a group boundary.
  The user must check ios->length or ios->nrpages to see
  how much IO will be preformed. It is the responsibility
  of the user to re-issue the reminder of the IO.

* Modify exofs To copy spilled pages on to the next IO.
  This means one last kick is needed after all coalescing
  of pages is done.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

1 files changed, 85 insertions, 15 deletions

diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index 61b2f7e5cdbd..d87c1f7562fb 100644
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -259,6 +259,46 @@ static void _unlock_pcol_pages(struct page_collect *pcol, int ret, int rw)
         }
 }
 
+static int _maybe_not_all_in_one_io(struct ore_io_state *ios,
+        struct page_collect *pcol_src, struct page_collect *pcol)
+{
+        /* length was wrong or offset was not page aligned */
+        BUG_ON(pcol_src->nr_pages < ios->nr_pages);
+
+        if (pcol_src->nr_pages > ios->nr_pages) {
+                struct page **src_page;
+                unsigned pages_less = pcol_src->nr_pages - ios->nr_pages;
+                unsigned long len_less = pcol_src->length - ios->length;
+                unsigned i;
+                int ret;
+
+                /* This IO was trimmed */
+                pcol_src->nr_pages = ios->nr_pages;
+                pcol_src->length = ios->length;
+
+                /* Left over pages are passed to the next io */
+                pcol->expected_pages += pages_less;
+                pcol->nr_pages = pages_less;
+                pcol->length = len_less;
+                src_page = pcol_src->pages + pcol_src->nr_pages;
+                pcol->pg_first = (*src_page)->index;
+
+                ret = pcol_try_alloc(pcol);
+                if (unlikely(ret))
+                        return ret;
+
+                for (i = 0; i < pages_less; ++i)
+                        pcol->pages[i] = *src_page++;
+
+                EXOFS_DBGMSG("Length was adjusted nr_pages=0x%x "
+                        "pages_less=0x%x expected_pages=0x%x "
+                        "next_offset=0x%llx next_len=0x%lx\n",
+                        pcol_src->nr_pages, pages_less, pcol->expected_pages,
+                        pcol->pg_first * PAGE_SIZE, pcol->length);
+        }
+        return 0;
+}
+
 static int read_exec(struct page_collect *pcol)
 {
         struct exofs_i_info *oi = exofs_i(pcol->inode);
@@ -280,7 +320,6 @@ static int read_exec(struct page_collect *pcol)
 
         ios = pcol->ios;
         ios->pages = pcol->pages;
-        ios->nr_pages = pcol->nr_pages;
 
         if (pcol->read_4_write) {
                 ore_read(pcol->ios);
@@ -296,17 +335,23 @@ static int read_exec(struct page_collect *pcol)
         *pcol_copy = *pcol;
         ios->done = readpages_done;
         ios->private = pcol_copy;
+
+        /* pages ownership was passed to pcol_copy */
+        _pcol_reset(pcol);
+
+        ret = _maybe_not_all_in_one_io(ios, pcol_copy, pcol);
+        if (unlikely(ret))
+                goto err;
+
+        EXOFS_DBGMSG2("read_exec(0x%lx) offset=0x%llx length=0x%llx\n",
+                pcol->inode->i_ino, _LLU(ios->offset), _LLU(ios->length));
+
         ret = ore_read(ios);
         if (unlikely(ret))
                 goto err;
 
         atomic_inc(&pcol->sbi->s_curr_pending);
 
-        EXOFS_DBGMSG2("read_exec obj=0x%llx start=0x%llx length=0x%lx\n",
-                  oi->one_comp.obj.id, _LLU(ios->offset), pcol->length);
-
-        /* pages ownership was passed to pcol_copy */
-        _pcol_reset(pcol);
         return 0;
 
 err:
@@ -429,6 +474,10 @@ static int exofs_readpages(struct file *file, struct address_space *mapping,
                 return ret;
         }
 
+        ret = read_exec(&pcol);
+        if (unlikely(ret))
+                return ret;
+
         return read_exec(&pcol);
 }
 
@@ -519,7 +568,6 @@ static int write_exec(struct page_collect *pcol)
         ret = ore_get_rw_state(&pcol->sbi->layout, &oi->oc, false,
                                  pcol->pg_first << PAGE_CACHE_SHIFT,
                                  pcol->length, &pcol->ios);
-
         if (unlikely(ret))
                 goto err;
 
@@ -534,10 +582,19 @@ static int write_exec(struct page_collect *pcol)
 
         ios = pcol->ios;
         ios->pages = pcol_copy->pages;
-        ios->nr_pages = pcol_copy->nr_pages;
         ios->done = writepages_done;
         ios->private = pcol_copy;
 
+        /* pages ownership was passed to pcol_copy */
+        _pcol_reset(pcol);
+
+        ret = _maybe_not_all_in_one_io(ios, pcol_copy, pcol);
+        if (unlikely(ret))
+                goto err;
+
+        EXOFS_DBGMSG2("write_exec(0x%lx) offset=0x%llx length=0x%llx\n",
+                pcol->inode->i_ino, _LLU(ios->offset), _LLU(ios->length));
+
         ret = ore_write(ios);
         if (unlikely(ret)) {
                 EXOFS_ERR("write_exec: ore_write() Failed\n");
@@ -545,11 +602,6 @@ static int write_exec(struct page_collect *pcol)
         }
 
         atomic_inc(&pcol->sbi->s_curr_pending);
-        EXOFS_DBGMSG2("write_exec(0x%lx, 0x%llx) start=0x%llx length=0x%lx\n",
-                  pcol->inode->i_ino, pcol->pg_first, _LLU(ios->offset),
-                  pcol->length);
-        /* pages ownership was passed to pcol_copy */
-        _pcol_reset(pcol);
         return 0;
 
 err:
@@ -689,12 +741,30 @@ static int exofs_writepages(struct address_space *mapping,
         _pcol_init(&pcol, expected_pages, mapping->host);
 
         ret = write_cache_pages(mapping, wbc, writepage_strip, &pcol);
-        if (ret) {
+        if (unlikely(ret)) {
                 EXOFS_ERR("write_cache_pages => %d\n", ret);
                 return ret;
         }
 
-        return write_exec(&pcol);
+        ret = write_exec(&pcol);
+        if (unlikely(ret))
+                return ret;
+
+        if (wbc->sync_mode == WB_SYNC_ALL) {
+                return write_exec(&pcol); /* pump the last reminder */
+        } else if (pcol.nr_pages) {
+                /* not SYNC let the reminder join the next writeout */
+                unsigned i;
+
+                for (i = 0; i < pcol.nr_pages; i++) {
+                        struct page *page = pcol.pages[i];
+
+                        end_page_writeback(page);
+                        set_page_dirty(page);
+                        unlock_page(page);
+                }
+        }
+        return 0;
 }
 
 static int exofs_writepage(struct page *page, struct writeback_control *wbc)