Hello, Tahsin.
FYI, this is the preliminary patch I'm trying to test. I'm running
the repro case w/o the patch but the bug hasn't triggered yet.
Thanks.
Index: work/include/linux/backing-dev.h
===================================================================
--- work.orig/include/linux/backing-dev.h
+++ work/include/linux/backing-dev.h
@@ -362,6 +362,26 @@ static inline struct bdi_writeback *inod
return inode->i_wb;
}
+static inline struct bdi_writeback *
+unlocked_inode_to_wb_lock_list(struct inode *inode)
+{
+ struct bdi_writeback *wb;
+
+ rcu_read_lock();
+
+ while (true) {
+ wb = inode->i_wb;
+ spin_lock(&wb->list_lock);
+ if (likely(wb == inode->i_wb))
+ break;
+ spin_unlock(&wb->list_lock);
+ cpu_relax();
+ }
+
+ rcu_read_unlock();
+ return wb;
+}
+
/**
* unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
* @inode: target inode
@@ -374,8 +394,7 @@ static inline struct bdi_writeback *inod
* unlocked_inode_to_wb_end().
*
* The caller must call unlocked_inode_to_wb_end() with *@lockdep
- * afterwards and can't sleep during transaction. IRQ may or may not be
- * disabled on return.
+ * afterwards and can't sleep during transaction.
*/
static inline struct bdi_writeback *
unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
@@ -388,14 +407,16 @@ unlocked_inode_to_wb_begin(struct inode
*/
*lockedp = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
- if (unlikely(*lockedp))
- spin_lock_irq(&inode->i_mapping->tree_lock);
-
/*
- * Protected by either !I_WB_SWITCH + rcu_read_lock() or tree_lock.
+ * Protected by either !I_WB_SWITCH + rcu_read_lock(),
* inode_to_wb() will bark. Deref directly.
*/
- return inode->i_wb;
+ if (likely(!*lockedp))
+ return inode->i_wb;
+
+ rcu_read_unlock();
+
+ return unlocked_inode_to_wb_lock_list(inode);
}
/**
@@ -405,10 +426,10 @@ unlocked_inode_to_wb_begin(struct inode
*/
static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
{
- if (unlikely(locked))
- spin_unlock_irq(&inode->i_mapping->tree_lock);
-
- rcu_read_unlock();
+ if (likely(!locked))
+ rcu_read_unlock();
+ else
+ spin_unlock(&inode->i_wb->list_lock);
}
#else /* CONFIG_CGROUP_WRITEBACK */
@@ -453,6 +474,15 @@ static inline struct bdi_writeback *inod
}
static inline struct bdi_writeback *
+unlocked_inode_to_wb_lock_list(struct inode *inode)
+{
+ struct bdi_writeback *wb = inode_to_wb(inode);
+
+ spin_lock(&wb->list_lock);
+ return wb;
+}
+
+static inline struct bdi_writeback *
unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
{
return inode_to_wb(inode);
Index: work/fs/fs-writeback.c
===================================================================
--- work.orig/fs/fs-writeback.c
+++ work/fs/fs-writeback.c
@@ -1309,10 +1309,10 @@ __writeback_single_inode(struct inode *i
* we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
* and does more profound writeback list handling in writeback_sb_inodes().
*/
-static int
-writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
- struct writeback_control *wbc)
+static int writeback_single_inode(struct inode *inode,
+ struct writeback_control *wbc)
{
+ struct bdi_writeback *wb;
int ret = 0;
spin_lock(&inode->i_lock);
@@ -1350,7 +1350,8 @@ writeback_single_inode(struct inode *ino
ret = __writeback_single_inode(inode, wbc);
wbc_detach_inode(wbc);
- spin_lock(&wb->list_lock);
+
+ wb = unlocked_inode_to_wb_lock_list(inode);
spin_lock(&inode->i_lock);
/*
* If inode is clean, remove it from writeback lists. Otherwise don't
@@ -1515,8 +1516,7 @@ static long writeback_sb_inodes(struct s
cond_resched();
}
-
- spin_lock(&wb->list_lock);
+ wb = unlocked_inode_to_wb_lock_list(inode);
spin_lock(&inode->i_lock);
if (!(inode->i_state & I_DIRTY_ALL))
wrote++;
@@ -2310,7 +2310,6 @@ EXPORT_SYMBOL(sync_inodes_sb);
*/
int write_inode_now(struct inode *inode, int sync)
{
- struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
struct writeback_control wbc = {
.nr_to_write = LONG_MAX,
.sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
@@ -2322,7 +2321,7 @@ int write_inode_now(struct inode *inode,
wbc.nr_to_write = 0;
might_sleep();
- return writeback_single_inode(inode, wb, &wbc);
+ return writeback_single_inode(inode, &wbc);
}
EXPORT_SYMBOL(write_inode_now);
@@ -2339,7 +2338,7 @@ EXPORT_SYMBOL(write_inode_now);
*/
int sync_inode(struct inode *inode, struct writeback_control *wbc)
{
- return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
+ return writeback_single_inode(inode, wbc);
}
EXPORT_SYMBOL(sync_inode);
--
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