exofs: Fix double page_unlock BUG in write_begin/end

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>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index eb7368ebd8cd..3eadd97324b1 100644
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -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);