[RFC] direct-io: btrfs: avoid splitting dio requests for non-btrfs filesystems

Commit Message

[e-mail] Nov. 2, 2010, 12:18 p.m. UTC

None

Patch

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c038644..1126185 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -37,6 +37,7 @@ 
 #include <linux/posix_acl.h>
 #include <linux/falloc.h>
 #include <linux/slab.h>
+#include <linux/aio.h>
 #include "compat.h"
 #include "ctree.h"
 #include "disk-io.h"
@@ -5822,6 +5823,9 @@  static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
 	free_extent_state(cached_state);
 	cached_state = NULL;
 
+	/* btrfs cannot handle logically non-contiguous requests */
+	kiocb_set_separate_meta_reads(iocb);
+
 	ret = __blockdev_direct_IO(rw, iocb, inode,
 		   BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev,
 		   iov, offset, nr_segs, btrfs_get_blocks_direct, NULL,
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 48d74c7..6d2dcb2 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -35,6 +35,7 @@ 
 #include <linux/buffer_head.h>
 #include <linux/rwsem.h>
 #include <linux/uio.h>
+#include <linux/aio.h>
 #include <asm/atomic.h>
 
 /*
@@ -79,6 +80,7 @@  struct dio {
 	sector_t final_block_in_request;/* doesn't change */
 	unsigned first_block_in_page;	/* doesn't change, Used only once */
 	int boundary;			/* prev block is at a boundary */
+	int separate_meta_reads;	/* separate in I/O submission */
 	int reap_counter;		/* rate limit reaping */
 	get_block_t *get_block;		/* block mapping function */
 	dio_iodone_t *end_io;		/* IO completion function */
@@ -659,7 +661,7 @@  static int dio_send_cur_page(struct dio *dio)
 		 * Submit now if the underlying fs is about to perform a
 		 * metadata read
 		 */
-		else if (dio->boundary)
+		else if (dio->separate_meta_reads &&  dio->boundary)
 			dio_bio_submit(dio);
 	}
 
@@ -1245,6 +1247,11 @@  __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
 		(end > i_size_read(inode)));
 
+	/*
+	 * some filesystems e.g. btrfs need to separate metadata read
+	 */
+	dio->separate_meta_reads = kiocb_needs_separate_meta_reads(iocb);
+
 	retval = direct_io_worker(rw, iocb, inode, iov, offset,
 				nr_segs, blkbits, get_block, end_io,
 				submit_io, dio);
diff --git a/include/linux/aio.h b/include/linux/aio.h
index 7a8db41..9ee9c6e 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -34,6 +34,8 @@  struct kioctx;
 /* #define KIF_LOCKED		0 */
 #define KIF_KICKED		1
 #define KIF_CANCELLED		2
+/* to separate meta reads */
+#define KIF_SEPARATE_META	3
 
 #define kiocbTryLock(iocb)	test_and_set_bit(KIF_LOCKED, &(iocb)->ki_flags)
 #define kiocbTryKick(iocb)	test_and_set_bit(KIF_KICKED, &(iocb)->ki_flags)
@@ -50,6 +52,9 @@  struct kioctx;
 #define kiocbIsKicked(iocb)	test_bit(KIF_KICKED, &(iocb)->ki_flags)
 #define kiocbIsCancelled(iocb)	test_bit(KIF_CANCELLED, &(iocb)->ki_flags)
 
+#define kiocb_set_separate_meta_reads(iocb)	set_bit(KIF_SEPARATE_META, &(iocb)->ki_flags)
+#define kiocb_needs_separate_meta_reads(iocb)	(KIF_SEPARATE_META & (iocb)->ki_flags)
+
 /* is there a better place to document function pointer methods? */
 /**
  * ki_retry	-	iocb forward progress callback