Processes can sleep in do_get_write_access(), waiting for buffers to be
removed from the BJ_Shadow state. We did this by doing a wake_up_buffer() in
the commit path and sleeping on the buffer in do_get_write_access().
With the filtered bit-level wakeup code this doesn't work properly any more -
the wake_up_buffer() accidentally wakes up tasks which are sleeping in
lock_buffer() as well. Those tasks now implicitly assume that the buffer came
unlocked. Net effect: Bogus I/O errors when reading journal blocks, because
the buffer isn't up to date yet. Hence the recently spate of journal_bmap()
failure reports.
The patch creates a new jbd-private BH flag purely for this wakeup function.
So a wake_up_bit(..., BH_Unshadow) doesn't wake up someone who is waiting for
a wake_up_bit(BH_Lock).
JBD was the only user of wake_up_buffer(), so remove it altogether.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/buffer.c | 11 ++---------
25-akpm/fs/jbd/commit.c | 2 +-
25-akpm/fs/jbd/transaction.c | 7 ++++---
25-akpm/include/linux/buffer_head.h | 1 -
25-akpm/include/linux/jbd.h | 1 +
5 files changed, 8 insertions(+), 14 deletions(-)
diff -puN fs/jbd/commit.c~jbd-wakeup-fix fs/jbd/commit.c
--- 25/fs/jbd/commit.c~jbd-wakeup-fix Mon Sep 20 15:38:55 2004
+++ 25-akpm/fs/jbd/commit.c Mon Sep 20 15:38:55 2004
@@ -577,7 +577,7 @@ wait_for_iobuf:
journal_file_buffer(jh, commit_transaction, BJ_Forget);
/* Wake up any transactions which were waiting for this
IO to complete */
- wake_up_buffer(bh);
+ wake_up_bit(&bh->b_state, BH_Unshadow);
JBUFFER_TRACE(jh, "brelse shadowed buffer");
__brelse(bh);
}
diff -puN fs/jbd/transaction.c~jbd-wakeup-fix fs/jbd/transaction.c
--- 25/fs/jbd/transaction.c~jbd-wakeup-fix Mon Sep 20 15:38:55 2004
+++ 25-akpm/fs/jbd/transaction.c Mon Sep 20 15:38:55 2004
@@ -633,9 +633,10 @@ repeat:
* disk then we cannot do copy-out here. */
if (jh->b_jlist == BJ_Shadow) {
- DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Lock);
- wait_queue_head_t *wqh
- = bit_waitqueue(&bh->b_state, BH_Lock);
+ DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow);
+ wait_queue_head_t *wqh;
+
+ wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
JBUFFER_TRACE(jh, "on shadow: sleep");
jbd_unlock_bh_state(bh);
diff -puN include/linux/jbd.h~jbd-wakeup-fix include/linux/jbd.h
--- 25/include/linux/jbd.h~jbd-wakeup-fix Mon Sep 20 15:38:55 2004
+++ 25-akpm/include/linux/jbd.h Mon Sep 20 15:38:55 2004
@@ -299,6 +299,7 @@ enum jbd_state_bits {
BH_JBDDirty, /* Is dirty but journaled */
BH_State, /* Pins most journal_head state */
BH_JournalHead, /* Pins bh->b_private and jh->b_bh */
+ BH_Unshadow, /* Dummy bit, for BJ_Shadow wakeup filtering */
};
BUFFER_FNS(JBD, jbd)
diff -puN include/linux/buffer_head.h~jbd-wakeup-fix include/linux/buffer_head.h
--- 25/include/linux/buffer_head.h~jbd-wakeup-fix Mon Sep 20 15:38:55 2004
+++ 25-akpm/include/linux/buffer_head.h Mon Sep 20 15:38:55 2004
@@ -155,7 +155,6 @@ void invalidate_bdev(struct block_device
int sync_blockdev(struct block_device *bdev);
void __wait_on_buffer(struct buffer_head *);
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
-void wake_up_buffer(struct buffer_head *bh);
int fsync_bdev(struct block_device *);
struct super_block *freeze_bdev(struct block_device *);
void thaw_bdev(struct block_device *, struct super_block *);
diff -puN fs/buffer.c~jbd-wakeup-fix fs/buffer.c
--- 25/fs/buffer.c~jbd-wakeup-fix Mon Sep 20 15:38:55 2004
+++ 25-akpm/fs/buffer.c Mon Sep 20 15:39:24 2004
@@ -52,13 +52,6 @@ init_buffer(struct buffer_head *bh, bh_e
bh->b_private = private;
}
-void wake_up_buffer(struct buffer_head *bh)
-{
- smp_mb();
- wake_up_bit(&bh->b_state, BH_Lock);
-}
-EXPORT_SYMBOL(wake_up_buffer);
-
static int sync_buffer(void *word)
{
struct block_device *bd;
@@ -83,8 +76,8 @@ EXPORT_SYMBOL(__lock_buffer);
void fastcall unlock_buffer(struct buffer_head *bh)
{
clear_buffer_locked(bh);
- smp_mb__after_clear_bit();
- wake_up_buffer(bh);
+ smp_mb();
+ wake_up_bit(&bh->b_state, BH_Lock);
}
/*
_