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>

diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index d87c1f7..96366a1 100644 (file)
--- 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",