diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0185-fs-dcache-disable-preemption-on-i_dir_seq-s-write-si.patch | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/debian/patches-rt/0185-fs-dcache-disable-preemption-on-i_dir_seq-s-write-si.patch b/debian/patches-rt/0185-fs-dcache-disable-preemption-on-i_dir_seq-s-write-si.patch new file mode 100644 index 000000000..e687b4d2d --- /dev/null +++ b/debian/patches-rt/0185-fs-dcache-disable-preemption-on-i_dir_seq-s-write-si.patch @@ -0,0 +1,99 @@ +From 06c5210bfc8eff16e0d1df2430c7fcb07eae6c67 Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Fri, 20 Oct 2017 11:29:53 +0200 +Subject: [PATCH 185/323] fs/dcache: disable preemption on i_dir_seq's write + side +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +i_dir_seq is an opencoded seqcounter. Based on the code it looks like we +could have two writers in parallel despite the fact that the d_lock is +held. The problem is that during the write process on RT the preemption +is still enabled and if this process is interrupted by a reader with RT +priority then we lock up. +To avoid that lock up I am disabling the preemption during the update. +The rename of i_dir_seq is here to ensure to catch new write sides in +future. + +Cc: stable-rt@vger.kernel.org +Reported-by: Oleg.Karfich@wago.com +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + fs/dcache.c | 12 +++++++----- + fs/inode.c | 2 +- + include/linux/fs.h | 2 +- + 3 files changed, 9 insertions(+), 7 deletions(-) + +diff --git a/fs/dcache.c b/fs/dcache.c +index 1f4255ef8722..26a187abf13a 100644 +--- a/fs/dcache.c ++++ b/fs/dcache.c +@@ -2503,9 +2503,10 @@ EXPORT_SYMBOL(d_rehash); + static inline unsigned start_dir_add(struct inode *dir) + { + ++ preempt_disable_rt(); + for (;;) { +- unsigned n = dir->i_dir_seq; +- if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n) ++ unsigned n = dir->__i_dir_seq; ++ if (!(n & 1) && cmpxchg(&dir->__i_dir_seq, n, n + 1) == n) + return n; + cpu_relax(); + } +@@ -2513,7 +2514,8 @@ static inline unsigned start_dir_add(struct inode *dir) + + static inline void end_dir_add(struct inode *dir, unsigned n) + { +- smp_store_release(&dir->i_dir_seq, n + 2); ++ smp_store_release(&dir->__i_dir_seq, n + 2); ++ preempt_enable_rt(); + } + + static void d_wait_lookup(struct dentry *dentry) +@@ -2549,7 +2551,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent, + + retry: + rcu_read_lock(); +- seq = smp_load_acquire(&parent->d_inode->i_dir_seq); ++ seq = smp_load_acquire(&parent->d_inode->__i_dir_seq); + r_seq = read_seqbegin(&rename_lock); + dentry = __d_lookup_rcu(parent, name, &d_seq); + if (unlikely(dentry)) { +@@ -2577,7 +2579,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent, + } + + hlist_bl_lock(b); +- if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) { ++ if (unlikely(READ_ONCE(parent->d_inode->__i_dir_seq) != seq)) { + hlist_bl_unlock(b); + rcu_read_unlock(); + goto retry; +diff --git a/fs/inode.c b/fs/inode.c +index 5c7139aa2bda..4ee8239c055f 100644 +--- a/fs/inode.c ++++ b/fs/inode.c +@@ -158,7 +158,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode) + inode->i_bdev = NULL; + inode->i_cdev = NULL; + inode->i_link = NULL; +- inode->i_dir_seq = 0; ++ inode->__i_dir_seq = 0; + inode->i_rdev = 0; + inode->dirtied_when = 0; + +diff --git a/include/linux/fs.h b/include/linux/fs.h +index 82316863c71f..a29a0b8a1eca 100644 +--- a/include/linux/fs.h ++++ b/include/linux/fs.h +@@ -699,7 +699,7 @@ struct inode { + struct block_device *i_bdev; + struct cdev *i_cdev; + char *i_link; +- unsigned i_dir_seq; ++ unsigned __i_dir_seq; + }; + + __u32 i_generation; +-- +2.43.0 + |