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[PATCH 01/27] xfs: PF_FSTRANS should never be set in ->writepage

To: xfs@xxxxxxxxxxx
Subject: [PATCH 01/27] xfs: PF_FSTRANS should never be set in ->writepage
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Fri, 01 Jul 2011 05:43:22 -0400
References: <20110701094321.936534538@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: quilt/0.48-1
Now that we reject direct reclaim in addition to always using GFP_NOFS
allocation there's no chance we'll ever end up in ->writepage with
PF_FSTRANS set.  Add a WARN_ON if we hit this case, and stop checking
if we'd actually need to start a transaction.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Alex Elder <aelder@xxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>

Index: xfs/fs/xfs/linux-2.6/xfs_aops.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_aops.c        2011-06-30 14:50:35.206501640 
+0200
+++ xfs/fs/xfs/linux-2.6/xfs_aops.c     2011-06-30 15:34:59.156468543 +0200
@@ -894,11 +894,6 @@ out_invalidate:
  * For unwritten space on the page we need to start the conversion to
  * regular allocated space.
  * For any other dirty buffer heads on the page we should flush them.
- *
- * If we detect that a transaction would be required to flush the page, we
- * have to check the process flags first, if we are already in a transaction
- * or disk I/O during allocations is off, we need to fail the writepage and
- * redirty the page.
  */
 STATIC int
 xfs_vm_writepage(
@@ -906,7 +901,6 @@ xfs_vm_writepage(
        struct writeback_control *wbc)
 {
        struct inode            *inode = page->mapping->host;
-       int                     delalloc, unwritten;
        struct buffer_head      *bh, *head;
        struct xfs_bmbt_irec    imap;
        xfs_ioend_t             *ioend = NULL, *iohead = NULL;
@@ -938,15 +932,10 @@ xfs_vm_writepage(
                goto redirty;
 
        /*
-        * We need a transaction if there are delalloc or unwritten buffers
-        * on the page.
-        *
-        * If we need a transaction and the process flags say we are already
-        * in a transaction, or no IO is allowed then mark the page dirty
-        * again and leave the page as is.
+        * Given that we do not allow direct reclaim to call us, we should
+        * never be called while in a filesystem transaction.
         */
-       xfs_count_page_state(page, &delalloc, &unwritten);
-       if ((current->flags & PF_FSTRANS) && (delalloc || unwritten))
+       if (WARN_ON(current->flags & PF_FSTRANS))
                goto redirty;
 
        /* Is this page beyond the end of the file? */

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