exofs: Fix double page_unlock BUG in write_begin/end
Boaz Harrosh [Thu, 7 Oct 2010 17:37:51 +0000 (13:37 -0400)]
This BUG is there since the first submit of the code, but only triggered
in last Kernel. It's timing related do to the asynchronous object-creation
behaviour of exofs. (Which should be investigated farther)

The bug is obvious hence the fixed.

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

fs/exofs/inode.c

index eb7368e..3eadd97 100644 (file)
@@ -54,6 +54,9 @@ struct page_collect {
        unsigned nr_pages;
        unsigned long length;
        loff_t pg_first; /* keep 64bit also in 32-arches */
+       bool read_4_write; /* This means two things: that the read is sync
+                           * And the pages should not be unlocked.
+                           */
 };
 
 static void _pcol_init(struct page_collect *pcol, unsigned expected_pages,
@@ -71,6 +74,7 @@ static void _pcol_init(struct page_collect *pcol, unsigned expected_pages,
        pcol->nr_pages = 0;
        pcol->length = 0;
        pcol->pg_first = -1;
+       pcol->read_4_write = false;
 }
 
 static void _pcol_reset(struct page_collect *pcol)
@@ -347,7 +351,8 @@ static int readpage_strip(void *data, struct page *page)
                if (PageError(page))
                        ClearPageError(page);
 
-               unlock_page(page);
+               if (!pcol->read_4_write)
+                       unlock_page(page);
                EXOFS_DBGMSG("readpage_strip(0x%lx, 0x%lx) empty page,"
                             " splitting\n", inode->i_ino, page->index);
 
@@ -428,6 +433,7 @@ static int _readpage(struct page *page, bool is_sync)
        /* readpage_strip might call read_exec(,is_sync==false) at several
         * places but not if we have a single page.
         */
+       pcol.read_4_write = is_sync;
        ret = readpage_strip(&pcol, page);
        if (ret) {
                EXOFS_ERR("_readpage => %d\n", ret);