xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular spinlock_t

Browse Source 
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
This commit is contained in:
Thomas Gleixner
2019-11-18 14:28:24 +01:00
parent fc32150e6f
commit f1e67e355c
4 changed files with 16 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
fs/buffer.c
View File

@@ -274,8 +274,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
* 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;
@@ -288,8 +287,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
}
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
@@ -301,8 +299,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
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;
}
@@ -371,8 +368,7 @@ void end_buffer_async_write(struct buffer_head *bh, int uptodate)
}
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);
@@ -384,14 +380,12 @@ void end_buffer_async_write(struct buffer_head *bh, int uptodate)
}
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);
@@ -3385,6 +3379,7 @@ struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
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();