[PATCH] blktrace: readahead support

Provide the needed kernel support for distinguishing readahead
from regular read requests when tracing block devices.

Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Jens Axboe <axboe@suse.de>

2 files changed, 5 insertions, 1 deletions

diff --git a/block/blktrace.c b/block/blktrace.c
index 92925e7d9e6c..b8c0702777ff 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -69,7 +69,7 @@ static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK
 /*
  * Bio action bits of interest
  */
-static u32 bio_act[3] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC) };
+static u32 bio_act[5] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC), 0, BLK_TC_ACT(BLK_TC_AHEAD) };
 
 /*
  * More could be added as needed, taking care to increment the decrementer
@@ -79,6 +79,8 @@ static u32 bio_act[3] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_AC
         (((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
 #define trace_sync_bit(rw)      \
         (((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
+#define trace_ahead_bit(rw)     \
+        (((rw) & (1 << BIO_RW_AHEAD)) << (BIO_RW_AHEAD - 0))
 
 /*
  * The worker for the various blk_add_trace*() types. Fills out a
@@ -100,6 +102,7 @@ void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
         what |= ddir_act[rw & WRITE];
         what |= bio_act[trace_barrier_bit(rw)];
         what |= bio_act[trace_sync_bit(rw)];
+        what |= bio_act[trace_ahead_bit(rw)];
 
         pid = tsk->pid;
         if (unlikely(act_log_check(bt, what, sector, pid)))
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index d95615fc6da5..2346a1db8561 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -19,6 +19,7 @@ enum blktrace_cat {
         BLK_TC_FS       = 1 << 8,       /* fs requests */
         BLK_TC_PC       = 1 << 9,       /* pc requests */
         BLK_TC_NOTIFY   = 1 << 10,      /* special message */
+        BLK_TC_AHEAD    = 1 << 11,      /* readahead */
 
         BLK_TC_END      = 1 << 15,      /* only 16-bits, reminder */
 };