exofs: Support for short read/writes

If at read/write_done the actual IO was shorter then requested,
reported in returned ios->length. It is not an error. The reminder
of the pages should just be unlocked but not marked uptodate or
end_page_writeback. They will be re issued later by the VFS.

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

1 files changed, 26 insertions, 9 deletions

diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index d87c1f7562fb..96366a1d7eae 100644
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -149,14 +149,17 @@ static int pcol_add_page(struct page_collect *pcol, struct page *page,
         return 0;
 }
 
+enum {PAGE_WAS_NOT_IN_IO = 17};
 static int update_read_page(struct page *page, int ret)
 {
-        if (ret == 0) {
+        switch (ret) {
+        case 0:
                 /* Everything is OK */
                 SetPageUptodate(page);
                 if (PageError(page))
                         ClearPageError(page);
-        } else if (ret == -EFAULT) {
+                break;
+        case -EFAULT:
                 /* In this case we were trying to read something that wasn't on
                  * disk yet - return a page full of zeroes.  This should be OK,
                  * because the object should be empty (if there was a write
@@ -167,16 +170,22 @@ static int update_read_page(struct page *page, int ret)
                 SetPageUptodate(page);
                 if (PageError(page))
                         ClearPageError(page);
-                ret = 0; /* recovered error */
                 EXOFS_DBGMSG("recovered read error\n");
-        } else /* Error */
+                /* fall through */
+        case PAGE_WAS_NOT_IN_IO:
+                ret = 0; /* recovered error */
+                break;
+        default:
                 SetPageError(page);
-
+        }
         return ret;
 }
 
 static void update_write_page(struct page *page, int ret)
 {
+        if (unlikely(ret == PAGE_WAS_NOT_IN_IO))
+                return; /* don't pass start don't collect $200 */
+
         if (ret) {
                 mapping_set_error(page->mapping, ret);
                 SetPageError(page);
@@ -195,10 +204,14 @@ static int __readpages_done(struct page_collect *pcol)
         u64 length = 0;
         int ret = ore_check_io(pcol->ios, &resid);
 
-        if (likely(!ret))
+        if (likely(!ret)) {
                 good_bytes = pcol->length;
-        else
+                ret = PAGE_WAS_NOT_IN_IO;
+        } else {
                 good_bytes = pcol->length - resid;
+        }
+        if (good_bytes > pcol->ios->length)
+                good_bytes = pcol->ios->length;
 
         EXOFS_DBGMSG2("readpages_done(0x%lx) good_bytes=0x%llx"
                      " length=0x%lx nr_pages=%u\n",
@@ -518,10 +531,14 @@ static void writepages_done(struct ore_io_state *ios, void *p)
 
         atomic_dec(&pcol->sbi->s_curr_pending);
 
-        if (likely(!ret))
+        if (likely(!ret)) {
                 good_bytes = pcol->length;
-        else
+                ret = PAGE_WAS_NOT_IN_IO;
+        } else {
                 good_bytes = pcol->length - resid;
+        }
+        if (good_bytes > pcol->ios->length)
+                good_bytes = pcol->ios->length;
 
         EXOFS_DBGMSG2("writepages_done(0x%lx) good_bytes=0x%llx"
                      " length=0x%lx nr_pages=%u\n",