From: Christoph Hellwig <hch@lst.de>
On Fri, Dec 10, 2004 at 11:04:22AM +1100, Nathan Scott wrote:
> The bug# for the write deadlock I mentioned earlier -- 925836.
I finally found some time to look at it, and this fix is almost trivial.
XFS doesn't need the i_alloc_sem at all, so we should avoid taking it in
direct-io.c completely. As a side-effect it makes the code a little bit
simpler even.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/direct-io.c | 13 +++++++------
1 files changed, 7 insertions(+), 6 deletions(-)
diff -puN fs/direct-io.c~direct-write-vs-truncate-deadlock fs/direct-io.c
--- 25/fs/direct-io.c~direct-write-vs-truncate-deadlock 2005-01-10 17:29:27.236746304 -0800
+++ 25-akpm/fs/direct-io.c 2005-01-10 17:29:27.240745696 -0800
@@ -215,7 +215,7 @@ static void dio_complete(struct dio *dio
{
if (dio->end_io && dio->result)
dio->end_io(dio->inode, offset, bytes, dio->map_bh.b_private);
- if (dio->lock_type != DIO_NO_LOCKING)
+ if (dio->lock_type == DIO_LOCKING)
up_read(&dio->inode->i_alloc_sem);
}
@@ -1201,8 +1201,8 @@ __blockdev_direct_IO(int rw, struct kioc
* readers need to grab i_sem and i_alloc_sem
* writers need to grab i_alloc_sem only (i_sem is already held)
* For regular files using DIO_OWN_LOCKING,
- * readers need to grab i_alloc_sem only (i_sem is already held)
- * writers need to grab i_alloc_sem only
+ * neither readers nor writers take any locks here
+ * (i_sem is already held and release for writers here)
*/
dio->lock_type = dio_lock_type;
if (dio_lock_type != DIO_NO_LOCKING) {
@@ -1219,14 +1219,15 @@ __blockdev_direct_IO(int rw, struct kioc
kfree(dio);
goto out;
}
- down_read(&inode->i_alloc_sem);
+
if (dio_lock_type == DIO_OWN_LOCKING) {
up(&inode->i_sem);
reader_with_isem = 0;
}
- } else {
- down_read(&inode->i_alloc_sem);
}
+
+ if (dio_lock_type == DIO_LOCKING)
+ down_read(&inode->i_alloc_sem);
}
/*
_