From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 18 Nov 2019 14:28:24 +0100
Subject: fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular spinlock_t
Patch-mainline: v5.7-rc1
Git-commit: f1e67e355c2aafeddf1eac31335709236996d2fe
References: bsc#1162702
Bit spinlocks are problematic if PREEMPT_RT is enabled, because they
disable preemption, which is undesired for latency reasons and breaks when
regular spinlocks are taken within the bit_spinlock locked region because
regular spinlocks are converted to 'sleeping spinlocks' on RT.
PREEMPT_RT replaced the bit spinlocks with regular spinlocks to avoid this
problem. The replacement was done conditionaly at compile time, but
Christoph requested to do an unconditional conversion.
Jan suggested to move the spinlock into a existing padding hole which
avoids a size increase of struct buffer_head on production kernels.
As a benefit the lock gains lockdep coverage.
[ bigeasy: Remove the wrapper and use always spinlock_t and move it into
the padding hole ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Link: https://lkml.kernel.org/r/20191118132824.rclhrbujqh4b4g4d@linutronix.de
Acked-by: Daniel Wagner <dwagner@suse.de>
---
fs/buffer.c | 19 +++++++------------
fs/ext4/page-io.c | 8 +++-----
fs/ntfs/aops.c | 9 +++------
include/linux/buffer_head.h | 6 +++---
4 files changed, 16 insertions(+), 26 deletions(-)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -275,8 +275,7 @@ static void end_buffer_async_read(struct
* decide that the page is now completely done.
*/
first = page_buffers(page);
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+ spin_lock_irqsave(&first->b_uptodate_lock, flags);
clear_buffer_async_read(bh);
unlock_buffer(bh);
tmp = bh;
@@ -289,8 +288,7 @@ static void end_buffer_async_read(struct
}
tmp = tmp->b_this_page;
} while (tmp != bh);
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
/*
* If none of the buffers had errors and they are all
@@ -302,8 +300,7 @@ static void end_buffer_async_read(struct
return;
still_busy:
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
return;
}
@@ -331,8 +328,7 @@ void end_buffer_async_write(struct buffe
}
first = page_buffers(page);
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+ spin_lock_irqsave(&first->b_uptodate_lock, flags);
clear_buffer_async_write(bh);
unlock_buffer(bh);
@@ -344,14 +340,12 @@ void end_buffer_async_write(struct buffe
}
tmp = tmp->b_this_page;
}
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
end_page_writeback(page);
return;
still_busy:
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
return;
}
EXPORT_SYMBOL(end_buffer_async_write);
@@ -3368,6 +3362,7 @@ struct buffer_head *alloc_buffer_head(gf
struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
if (ret) {
INIT_LIST_HEAD(&ret->b_assoc_buffers);
+ spin_lock_init(&ret->b_uptodate_lock);
preempt_disable();
__this_cpu_inc(bh_accounting.nr);
recalc_bh_state();
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -87,11 +87,10 @@ static void ext4_finish_bio(struct bio *
}
bh = head = page_buffers(page);
/*
- * We check all buffers in the page under BH_Uptodate_Lock
+ * We check all buffers in the page under b_uptodate_lock
* to avoid races with other end io clearing async_write flags
*/
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
+ spin_lock_irqsave(&head->b_uptodate_lock, flags);
do {
if (bh_offset(bh) < bio_start ||
bh_offset(bh) + bh->b_size > bio_end) {
@@ -103,8 +102,7 @@ static void ext4_finish_bio(struct bio *
if (bio->bi_status)
buffer_io_error(bh);
} while ((bh = bh->b_this_page) != head);
- bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&head->b_uptodate_lock, flags);
if (!under_io) {
fscrypt_free_bounce_page(bounce_page);
end_page_writeback(page);
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -92,8 +92,7 @@ static void ntfs_end_buffer_async_read(s
"0x%llx.", (unsigned long long)bh->b_blocknr);
}
first = page_buffers(page);
- local_irq_save(flags);
- bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
+ spin_lock_irqsave(&first->b_uptodate_lock, flags);
clear_buffer_async_read(bh);
unlock_buffer(bh);
tmp = bh;
@@ -108,8 +107,7 @@ static void ntfs_end_buffer_async_read(s
}
tmp = tmp->b_this_page;
} while (tmp != bh);
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
/*
* If none of the buffers had errors then we can set the page uptodate,
* but we first have to perform the post read mst fixups, if the
@@ -142,8 +140,7 @@ static void ntfs_end_buffer_async_read(s
unlock_page(page);
return;
still_busy:
- bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
return;
}
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -22,9 +22,6 @@ enum bh_state_bits {
BH_Dirty, /* Is dirty */
BH_Lock, /* Is locked */
BH_Req, /* Has been submitted for I/O */
- BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
- * IO completion of other buffers in the page
- */
BH_Mapped, /* Has a disk mapping */
BH_New, /* Disk mapping was newly created by get_block */
@@ -76,6 +73,9 @@ struct buffer_head {
struct address_space *b_assoc_map; /* mapping this buffer is
associated with */
atomic_t b_count; /* users using this buffer_head */
+ spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to
+ * serialise IO completion of other
+ * buffers in the page */
};
/*