[XFS] Delay I/O completion for unwritten extents after conversion

SGI-PV: 936584
SGI-Modid: xfs-linux:xfs-kern:196886a

Signed-off-by: Christoph Hellwig <hch@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>

2 files changed, 26 insertions, 2 deletions

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 2add9a8a8df7..ea615e2f476d 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -136,10 +136,21 @@ xfs_end_bio_unwritten(
         vnode_t                 *vp = ioend->io_vnode;
         xfs_off_t               offset = ioend->io_offset;
         size_t                  size = ioend->io_size;
+        struct buffer_head      *bh, *next;
         int                     error;
 
         if (ioend->io_uptodate)
                 VOP_BMAP(vp, offset, size, BMAPI_UNWRITTEN, NULL, NULL, error);
+
+        /* ioend->io_buffer_head is only non-NULL for buffered I/O */
+        for (bh = ioend->io_buffer_head; bh; bh = next) {
+                next = bh->b_private;
+
+                bh->b_end_io = NULL;
+                clear_buffer_unwritten(bh);
+                end_buffer_async_write(bh, ioend->io_uptodate);
+        }
+
         xfs_destroy_ioend(ioend);
 }
 
@@ -165,6 +176,7 @@ xfs_alloc_ioend(
         atomic_set(&ioend->io_remaining, 1);
         ioend->io_uptodate = 1; /* cleared if any I/O fails */
         ioend->io_vnode = LINVFS_GET_VP(inode);
+        ioend->io_buffer_head = NULL;
         atomic_inc(&ioend->io_vnode->v_iocount);
         ioend->io_offset = 0;
         ioend->io_size = 0;
@@ -180,15 +192,26 @@ linvfs_unwritten_done(
         int                     uptodate)
 {
         xfs_ioend_t             *ioend = bh->b_private;
+        static spinlock_t       unwritten_done_lock = SPIN_LOCK_UNLOCKED;
+        unsigned long           flags;
 
         ASSERT(buffer_unwritten(bh));
         bh->b_end_io = NULL;
-        clear_buffer_unwritten(bh);
+
         if (!uptodate)
                 ioend->io_uptodate = 0;
 
+        /*
+         * Deep magic here.  We reuse b_private in the buffer_heads to build
+         * a chain for completing the I/O from user context after we've issued
+         * a transaction to convert the unwritten extent.
+         */
+        spin_lock_irqsave(&unwritten_done_lock, flags);
+        bh->b_private = ioend->io_buffer_head;
+        ioend->io_buffer_head = bh;
+        spin_unlock_irqrestore(&unwritten_done_lock, flags);
+
         xfs_finish_ioend(ioend);
-        end_buffer_async_write(bh, uptodate);
 }
 
 STATIC int
diff --git a/fs/xfs/linux-2.6/xfs_aops.h b/fs/xfs/linux-2.6/xfs_aops.h
index ee46307a7321..2fa62974a04d 100644
--- a/fs/xfs/linux-2.6/xfs_aops.h
+++ b/fs/xfs/linux-2.6/xfs_aops.h
@@ -41,6 +41,7 @@ typedef struct xfs_ioend {
         unsigned int            io_uptodate;    /* I/O status register */
         atomic_t                io_remaining;   /* hold count */
         struct vnode            *io_vnode;      /* file being written to */
+        struct buffer_head      *io_buffer_head;/* buffer linked list head */
         size_t                  io_size;        /* size of the extent */
         xfs_off_t               io_offset;      /* offset in the file */
         struct work_struct      io_work;        /* xfsdatad work queue */