fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular spinlock_t
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. So RT replaces the bit spinlocks with regular spinlocks to avoid this problem. Bit spinlocks are also not covered by lock debugging, e.g. lockdep. Substitute the BH_Uptodate_Lock bit spinlock with a regular spinlock. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> [bigeasy: remove the wrapper and use always spinlock_t and move it into the padding hole] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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9eb30832cc
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f010667d40
19
fs/buffer.c
19
fs/buffer.c
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@ -275,8 +275,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
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* decide that the page is now completely done.
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*/
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first = page_buffers(page);
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local_irq_save(flags);
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bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
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spin_lock_irqsave(&first->b_uptodate_lock, flags);
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clear_buffer_async_read(bh);
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unlock_buffer(bh);
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tmp = bh;
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@ -289,8 +288,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
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}
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tmp = tmp->b_this_page;
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} while (tmp != bh);
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
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/*
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* If none of the buffers had errors and they are all
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@ -302,8 +300,7 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
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return;
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still_busy:
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
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return;
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}
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@ -331,8 +328,7 @@ void end_buffer_async_write(struct buffer_head *bh, int uptodate)
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}
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first = page_buffers(page);
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local_irq_save(flags);
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bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
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spin_lock_irqsave(&first->b_uptodate_lock, flags);
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clear_buffer_async_write(bh);
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unlock_buffer(bh);
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@ -344,14 +340,12 @@ void end_buffer_async_write(struct buffer_head *bh, int uptodate)
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}
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tmp = tmp->b_this_page;
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}
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
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end_page_writeback(page);
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return;
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still_busy:
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
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return;
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}
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EXPORT_SYMBOL(end_buffer_async_write);
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@ -3349,6 +3343,7 @@ struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
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struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
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if (ret) {
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INIT_LIST_HEAD(&ret->b_assoc_buffers);
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spin_lock_init(&ret->b_uptodate_lock);
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preempt_disable();
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__this_cpu_inc(bh_accounting.nr);
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recalc_bh_state();
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@ -87,11 +87,10 @@ static void ext4_finish_bio(struct bio *bio)
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}
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bh = head = page_buffers(page);
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/*
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* We check all buffers in the page under BH_Uptodate_Lock
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* We check all buffers in the page under b_uptodate_lock
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* to avoid races with other end io clearing async_write flags
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*/
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local_irq_save(flags);
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bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
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spin_lock_irqsave(&head->b_uptodate_lock, flags);
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do {
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if (bh_offset(bh) < bio_start ||
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bh_offset(bh) + bh->b_size > bio_end) {
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@ -105,8 +104,7 @@ static void ext4_finish_bio(struct bio *bio)
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buffer_io_error(bh);
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}
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} while ((bh = bh->b_this_page) != head);
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bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&head->b_uptodate_lock, flags);
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if (!under_io) {
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fscrypt_free_bounce_page(bounce_page);
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end_page_writeback(page);
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@ -92,8 +92,7 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
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"0x%llx.", (unsigned long long)bh->b_blocknr);
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}
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first = page_buffers(page);
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local_irq_save(flags);
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bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
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spin_lock_irqsave(&first->b_uptodate_lock, flags);
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clear_buffer_async_read(bh);
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unlock_buffer(bh);
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tmp = bh;
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@ -108,8 +107,7 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
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}
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tmp = tmp->b_this_page;
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} while (tmp != bh);
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
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/*
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* If none of the buffers had errors then we can set the page uptodate,
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* but we first have to perform the post read mst fixups, if the
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@ -142,8 +140,7 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
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unlock_page(page);
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return;
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still_busy:
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bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
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return;
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}
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@ -22,9 +22,6 @@ enum bh_state_bits {
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BH_Dirty, /* Is dirty */
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BH_Lock, /* Is locked */
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BH_Req, /* Has been submitted for I/O */
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BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
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* IO completion of other buffers in the page
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*/
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BH_Mapped, /* Has a disk mapping */
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BH_New, /* Disk mapping was newly created by get_block */
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@ -76,6 +73,9 @@ struct buffer_head {
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struct address_space *b_assoc_map; /* mapping this buffer is
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associated with */
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atomic_t b_count; /* users using this buffer_head */
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spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to
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* serialise IO completion of other
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* buffers in the page */
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};
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/*
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