diff options
Diffstat (limited to 'debian/patches-rt/fs-buffer-Make-BH_Uptodate_Lock-bit_spin_lock-a-regu.patch')
| -rw-r--r-- | debian/patches-rt/fs-buffer-Make-BH_Uptodate_Lock-bit_spin_lock-a-regu.patch | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/debian/patches-rt/fs-buffer-Make-BH_Uptodate_Lock-bit_spin_lock-a-regu.patch b/debian/patches-rt/fs-buffer-Make-BH_Uptodate_Lock-bit_spin_lock-a-regu.patch new file mode 100644 index 000000000..3669e87b2 --- /dev/null +++ b/debian/patches-rt/fs-buffer-Make-BH_Uptodate_Lock-bit_spin_lock-a-regu.patch @@ -0,0 +1,193 @@ +From: Thomas Gleixner <tglx@linutronix.de> +Date: Fri, 15 Nov 2019 18:54:20 +0100 +Subject: [PATCH] fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular + spinlock_t +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.3-rt1.tar.xz + +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> +--- +v2…v3: rename uptodate_lock to b_uptodate_lock. + +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(-) + +--- 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 */ + }; + + /* |