xfs: truncate delalloc extents when IO fails in writeback

[pandora-kernel.git] / fs / xfs / linux-2.6 / xfs_aops.c

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 793908a..9083357 100644 (file)
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -39,6 +39,7 @@
 #include "xfs_iomap.h"
 #include "xfs_vnodeops.h"
 #include "xfs_trace.h"
+#include "xfs_bmap.h"
 #include <linux/mpage.h>
 #include <linux/pagevec.h>
 #include <linux/writeback.h>
@@ -893,6 +894,118 @@ xfs_cluster_write(
        }
 }
 
+STATIC void
+xfs_vm_invalidatepage(
+       struct page             *page,
+       unsigned long           offset)
+{
+       trace_xfs_invalidatepage(page->mapping->host, page, offset);
+       block_invalidatepage(page, offset);
+}
+
+/*
+ * If the page has delalloc buffers on it, we need to punch them out before we
+ * invalidate the page. If we don't, we leave a stale delalloc mapping on the
+ * inode that can trip a BUG() in xfs_get_blocks() later on if a direct IO read
+ * is done on that same region - the delalloc extent is returned when none is
+ * supposed to be there.
+ *
+ * We prevent this by truncating away the delalloc regions on the page before
+ * invalidating it. Because they are delalloc, we can do this without needing a
+ * transaction. Indeed - if we get ENOSPC errors, we have to be able to do this
+ * truncation without a transaction as there is no space left for block
+ * reservation (typically why we see a ENOSPC in writeback).
+ *
+ * This is not a performance critical path, so for now just do the punching a
+ * buffer head at a time.
+ */
+STATIC void
+xfs_aops_discard_page(
+       struct page             *page)
+{
+       struct inode            *inode = page->mapping->host;
+       struct xfs_inode        *ip = XFS_I(inode);
+       struct buffer_head      *bh, *head;
+       loff_t                  offset = page_offset(page);
+       ssize_t                 len = 1 << inode->i_blkbits;
+
+       if (!xfs_is_delayed_page(page, IOMAP_DELAY))
+               goto out_invalidate;
+
+       xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
+               "page discard on page %p, inode 0x%llx, offset %llu.",
+                       page, ip->i_ino, offset);
+
+       xfs_ilock(ip, XFS_ILOCK_EXCL);
+       bh = head = page_buffers(page);
+       do {
+               int             done;
+               xfs_fileoff_t   offset_fsb;
+               xfs_bmbt_irec_t imap;
+               int             nimaps = 1;
+               int             error;
+               xfs_fsblock_t   firstblock;
+               xfs_bmap_free_t flist;
+
+               if (!buffer_delay(bh))
+                       goto next_buffer;
+
+               offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
+
+               /*
+                * Map the range first and check that it is a delalloc extent
+                * before trying to unmap the range. Otherwise we will be
+                * trying to remove a real extent (which requires a
+                * transaction) or a hole, which is probably a bad idea...
+                */
+               error = xfs_bmapi(NULL, ip, offset_fsb, 1,
+                               XFS_BMAPI_ENTIRE,  NULL, 0, &imap,
+                               &nimaps, NULL, NULL);
+
+               if (error) {
+                       /* something screwed, just bail */
+                       xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
+                       "page discard failed delalloc mapping lookup.");
+                       break;
+               }
+               if (!nimaps) {
+                       /* nothing there */
+                       goto next_buffer;
+               }
+               if (imap.br_startblock != DELAYSTARTBLOCK) {
+                       /* been converted, ignore */
+                       goto next_buffer;
+               }
+               WARN_ON(imap.br_blockcount == 0);
+
+               /*
+                * Note: while we initialise the firstblock/flist pair, they
+                * should never be used because blocks should never be
+                * allocated or freed for a delalloc extent and hence we need
+                * don't cancel or finish them after the xfs_bunmapi() call.
+                */
+               xfs_bmap_init(&flist, &firstblock);
+               error = xfs_bunmapi(NULL, ip, offset_fsb, 1, 0, 1, &firstblock,
+                                       &flist, NULL, &done);
+
+               ASSERT(!flist.xbf_count && !flist.xbf_first);
+               if (error) {
+                       /* something screwed, just bail */
+                       xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
+                       "page discard unable to remove delalloc mapping.");
+                       break;
+               }
+next_buffer:
+               offset += len;
+
+       } while ((bh = bh->b_this_page) != head);
+
+       xfs_iunlock(ip, XFS_ILOCK_EXCL);
+out_invalidate:
+       xfs_vm_invalidatepage(page, 0);
+       return;
+}
+
 /*
  * Calling this without startio set means we are being asked to make a dirty
  * page ready for freeing it's buffers.  When called with startio set then
@@ -1144,7 +1257,7 @@ error:
         */
        if (err != -EAGAIN) {
                if (!unmapped)
-                       block_invalidatepage(page, 0);
+                       xfs_aops_discard_page(page);
                ClearPageUptodate(page);
        }
        return err;
@@ -1554,15 +1667,6 @@ xfs_vm_readpages(
        return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);
 }
 
-STATIC void
-xfs_vm_invalidatepage(
-       struct page             *page,
-       unsigned long           offset)
-{
-       trace_xfs_invalidatepage(page->mapping->host, page, offset);
-       block_invalidatepage(page, offset);
-}
-
 const struct address_space_operations xfs_address_space_operations = {
        .readpage               = xfs_vm_readpage,
        .readpages              = xfs_vm_readpages,