[PATCH] Fix and add EXPORT_SYMBOL(filemap_write_and_wait)

This patch add EXPORT_SYMBOL(filemap_write_and_wait) and use it.

See mm/filemap.c:

And changes the filemap_write_and_wait() and filemap_write_and_wait_range().

Current filemap_write_and_wait() doesn't wait if filemap_fdatawrite()
returns error.  However, even if filemap_fdatawrite() returned an
error, it may have submitted the partially data pages to the device.
(e.g. in the case of -ENOSPC)

<quotation>
Andrew Morton writes,

If filemap_fdatawrite() returns an error, this might be due to some
I/O problem: dead disk, unplugged cable, etc.  Given the generally
crappy quality of the kernel's handling of such exceptions, there's a
good chance that the filemap_fdatawait() will get stuck in D state
forever.
</quotation>

So, this patch doesn't wait if filemap_fdatawrite() returns the -EIO.

Trond, could you please review the nfs part?  Especially I'm not sure,
nfs must use the "filemap_fdatawrite(inode->i_mapping) == 0", or not.

Acked-by: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 27 insertions, 13 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 8fdf36508023..478f4c74cc31 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -343,30 +343,44 @@ EXPORT_SYMBOL(filemap_fdatawait);
 
 int filemap_write_and_wait(struct address_space *mapping)
 {
-        int retval = 0;
+        int err = 0;
 
         if (mapping->nrpages) {
-                retval = filemap_fdatawrite(mapping);
-                if (retval == 0)
-                        retval = filemap_fdatawait(mapping);
+                err = filemap_fdatawrite(mapping);
+                /*
+                 * Even if the above returned error, the pages may be
+                 * written partially (e.g. -ENOSPC), so we wait for it.
+                 * But the -EIO is special case, it may indicate the worst
+                 * thing (e.g. bug) happened, so we avoid waiting for it.
+                 */
+                if (err != -EIO) {
+                        int err2 = filemap_fdatawait(mapping);
+                        if (!err)
+                                err = err2;
+                }
         }
-        return retval;
+        return err;
 }
+EXPORT_SYMBOL(filemap_write_and_wait);
 
 int filemap_write_and_wait_range(struct address_space *mapping,
                                  loff_t lstart, loff_t lend)
 {
-        int retval = 0;
+        int err = 0;
 
         if (mapping->nrpages) {
-                retval = __filemap_fdatawrite_range(mapping, lstart, lend,
-                                                    WB_SYNC_ALL);
-                if (retval == 0)
-                        retval = wait_on_page_writeback_range(mapping,
-                                                    lstart >> PAGE_CACHE_SHIFT,
-                                                    lend >> PAGE_CACHE_SHIFT);
+                err = __filemap_fdatawrite_range(mapping, lstart, lend,
+                                                 WB_SYNC_ALL);
+                /* See comment of filemap_write_and_wait() */
+                if (err != -EIO) {
+                        int err2 = wait_on_page_writeback_range(mapping,
+                                                lstart >> PAGE_CACHE_SHIFT,
+                                                lend >> PAGE_CACHE_SHIFT);
+                        if (!err)
+                                err = err2;
+                }
         }
-        return retval;
+        return err;
 }
 
 /*