From patchwork Fri Nov 15 17:54:20 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sebastian Sewior X-Patchwork-Id: 11246923 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B2AA713B2 for ; Fri, 15 Nov 2019 17:54:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B1222073C for ; Fri, 15 Nov 2019 17:54:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726308AbfKORyd convert rfc822-to-8bit (ORCPT ); Fri, 15 Nov 2019 12:54:33 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:44188 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726131AbfKORyd (ORCPT ); Fri, 15 Nov 2019 12:54:33 -0500 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1iVfnY-0004ix-Pc; Fri, 15 Nov 2019 18:54:20 +0100 Date: Fri, 15 Nov 2019 18:54:20 +0100 From: Sebastian Siewior To: Jan Kara Cc: Thomas Gleixner , Matthew Wilcox , LKML , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Anna-Maria Gleixner , Steven Rostedt , Julia Cartwright , Theodore Tso , Alexander Viro , Jan Kara , Mark Fasheh , Joseph Qi , Christoph Hellwig , Joel Becker Subject: [PATCH v2] fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular spinlock_t Message-ID: <20191115175420.cotwwz5tmcwvllsq@linutronix.de> References: <20190820170818.oldsdoumzashhcgh@linutronix.de> <20190820171721.GA4949@bombadil.infradead.org> <20191011112525.7dksg6ixb5c3hxn5@linutronix.de> <20191115145638.GA5461@quack2.suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191115145638.GA5461@quack2.suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Thomas Gleixner 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. Signed-off-by: Thomas Gleixner [bigeasy: remove the wrapper and use always spinlock_t and move it into the padding hole] Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Jan Kara --- v1…v2: Move the spinlock_t to the padding hole as per Jan Kara. pahole says its total size remained unchanged, before | atomic_t b_count; /* 96 4 */ | | /* size: 104, cachelines: 2, members: 12 */ | /* padding: 4 */ | /* last cacheline: 40 bytes */ after | atomic_t b_count; /* 96 4 */ | spinlock_t uptodate_lock; /* 100 4 */ | | /* size: 104, cachelines: 2, members: 13 */ | /* last cacheline: 40 bytes */ 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(-) diff --git a/fs/buffer.c b/fs/buffer.c index 0ac4ae15ea4dc..2c6f2b41a88e4 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -277,8 +277,7 @@ 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->uptodate_lock, flags); clear_buffer_async_read(bh); unlock_buffer(bh); tmp = bh; @@ -291,8 +290,7 @@ 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->uptodate_lock, flags); /* * If none of the buffers had errors and they are all @@ -304,8 +302,7 @@ 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->uptodate_lock, flags); return; } @@ -333,8 +330,7 @@ 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->uptodate_lock, flags); clear_buffer_async_write(bh); unlock_buffer(bh); @@ -346,14 +342,12 @@ 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->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->uptodate_lock, flags); return; } EXPORT_SYMBOL(end_buffer_async_write); @@ -3422,6 +3416,7 @@ 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->uptodate_lock); preempt_disable(); __this_cpu_inc(bh_accounting.nr); recalc_bh_state(); diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index 893913d1c2fe3..592816713e0d6 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -125,11 +125,10 @@ static void ext4_finish_bio(struct bio *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 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->uptodate_lock, flags); do { if (bh_offset(bh) < bio_start || bh_offset(bh) + bh->b_size > bio_end) { @@ -141,8 +140,7 @@ static void ext4_finish_bio(struct bio *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->uptodate_lock, flags); if (!under_io) { fscrypt_free_bounce_page(bounce_page); end_page_writeback(page); diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c index 7202a1e39d70c..14ca433b3a9e4 100644 --- a/fs/ntfs/aops.c +++ b/fs/ntfs/aops.c @@ -92,8 +92,7 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate) "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->uptodate_lock, flags); clear_buffer_async_read(bh); unlock_buffer(bh); tmp = bh; @@ -108,8 +107,7 @@ static void ntfs_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->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(struct buffer_head *bh, int uptodate) unlock_page(page); return; still_busy: - bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); - local_irq_restore(flags); + spin_unlock_irqrestore(&first->uptodate_lock, flags); return; } diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index 7b73ef7f902d4..e3f8421d17bab 100644 --- 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 uptodate_lock; /* Used by the first bh in a page, to + * serialise IO completion of other + * buffers in the page */ }; /*