+This patch is no longer needed for Lustre. It is only included
+for testing and ease of using the same kernel with older Lustre
+versions. This testing functionality was replaced in Linux 3.0
+by the dm-flakey driver.
+
+This functionality is mainly used during testing, in order to
+simulate a server crash for ldiskfs by discarding all of the
+writes to the filesystem. For recovery testing we could simulate
+this by using a special loopback or DM device that also discards
+writes to the device.
+
+This functionality is also used by target "failback" in order
+to speed up service shutdown and takeover by the other node
+during controlled operation. However, it would also be possible
+to do this by simply allowing all of the in-flight requests to
+complete and then waiting for the service to stop. This will
+also be needed by the DMU-OSD, because discarding of writes on
+a DMU-based target is not safe as it could trigger a storage
+failure if the data is ever read from disk again and the
+checksum does not match that expected by the block pointer.
+
Index: linux-2.6.27.21-0.1/block/blk-core.c
===================================================================
--- linux-2.6.27.21-0.1.orig/block/blk-core.c 2009-04-23 02:12:51.000000000 -0600
/*
* Check whether this bio extends beyond the end of the device.
*/
-@@ -1436,6 +1438,23 @@
+@@ -1436,6 +1438,12 @@
if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
goto end_io;
+ /* this is cfs's dev_rdonly check */
-+ if (bio->bi_rw == WRITE && dev_check_rdonly(bio->bi_bdev)) {
-+ struct block_device *bdev = bio->bi_bdev;
-+
-+ printk(KERN_WARNING "Write to readonly device %s (%#x) "
-+ "bi_flags: %lx, bi_vcnt: %d, bi_idx: %d, "
-+ "bi->size: %d, bi_cnt: %d, bi_private: %p\n",
-+ bdev->bd_disk ? bdev->bd_disk->disk_name : "",
-+ bdev->bd_dev, bio->bi_flags, bio->bi_vcnt,
-+ bio->bi_idx, bio->bi_size,
-+ atomic_read(&bio->bi_cnt), bio->bi_private);
-+ set_bit(BIO_RDONLY, &bio->bi_flags);
++ if (bio_rw(bio) == WRITE && dev_check_rdonly(bio->bi_bdev)) {
+ bio_endio(bio, bio->bi_size, 0);
-+ clear_bit(BIO_RDONLY, &bio->bi_flags);
+ break;
+ }
+
if (should_fail_request(bio))
goto end_io;
-@@ -2189,6 +2208,91 @@
+@@ -2189,6 +2197,91 @@
}
EXPORT_SYMBOL(kblockd_flush_work);
extern int set_blocksize(struct block_device *, int);
extern int sb_set_blocksize(struct super_block *, int);
extern int sb_min_blocksize(struct super_block *, int);
-Index: linux-2.6.27.21-0.1/include/linux/bio.h
-===================================================================
---- linux-2.6.27.21-0.1.orig/include/linux/bio.h 2009-05-22 08:38:00.000000000 -0600
-+++ linux-2.6.27.21-0.1/include/linux/bio.h 2009-05-22 08:38:02.000000000 -0600
-@@ -117,6 +117,7 @@
- #define BIO_CPU_AFFINE 8 /* complete bio on same CPU as submitted */
- #define BIO_FS_INTEGRITY 10 /* fs owns integrity data, not block layer */
- #define BIO_QUIET 11 /* Make BIO Quiet */
-+#define BIO_RDONLY 31 /* device is readonly */
- #define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))
-
- /*