From: Tejun Heo on
Commit a82afdf (block: use the same failfast bits for bio and request)
moved BIO_RW_* bits around such that they match up with REQ_* bits.
Unfortunately, fs.h hard coded READ, WRITE, READA and SWRITE as 0, 1,
2 and 3, and expected them to match with BIO_RW_* bits. READ/WRITE
didn't change but BIO_RW_AHEAD was moved to bit 4 instead of bit 1,
breaking READA and SWRITE.

This patch updates READA and SWRITE such that they match the BIO_RW_*
bits again. A follow up patch will update the definitions to directly
use BIO_RW_* bits so that this kind of breakage won't happen again.

Stable: The offending commit a82afdf was released with v2.6.32, so
this patch should be applied to all kernels since then but it must
_NOT_ be applied to kernels earlier than that.

Signed-off-by: Tejun Heo <tj(a)>
Reported-and-bisected-by: Vladislav Bolkhovitin <vst(a)>
Root-caused-by: Neil Brown <neilb(a)>
Cc: Jens Axobe <axboe(a)>
Cc: stable(a)
Aieee... thanks for root causing it Neil. That was a stupid bug. I
knew that READ/WRITE were hardcoded but forgot about READA. :-(
Moving BIO_RW_AHEAD back to bit 1 might be a better solution but I'm
afraid that would cause more confusions downstream. This patch
updates READA and SWRITE to match BIO_RW_AHEAD and should also appear
in -stable releases. The next patch will create bio_types.h and
define all constants in terms of BIO_RW_*.


include/linux/fs.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

Index: work/include/linux/fs.h
--- work.orig/include/linux/fs.h
+++ work/include/linux/fs.h
@@ -148,8 +148,8 @@ struct inodes_stat_t {
#define RWA_MASK 2
#define READ 0
#define WRITE 1
-#define READA 2 /* read-ahead - don't block if no resources */
-#define SWRITE 3 /* for ll_rw_block() - wait for buffer lock */
+#define READA 16 /* read-ahead - don't block if no resources */
+#define SWRITE 17 /* for ll_rw_block() - wait for buffer lock */
#define READ_SYNC (READ | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG))
#define READ_META (READ | (1 << BIO_RW_META))
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