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-rw-r--r--fs/fs-writeback.c345
1 files changed, 158 insertions, 187 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 628235cf44b..8e1e5e19d21 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -35,21 +35,29 @@
int nr_pdflush_threads;
/*
+ * Passed into wb_writeback(), essentially a subset of writeback_control
+ */
+struct wb_writeback_args {
+ long nr_pages;
+ struct super_block *sb;
+ enum writeback_sync_modes sync_mode;
+ int for_kupdate;
+ int range_cyclic;
+};
+
+/*
* Work items for the bdi_writeback threads
*/
struct bdi_work {
- struct list_head list;
- struct list_head wait_list;
- struct rcu_head rcu_head;
+ struct list_head list; /* pending work list */
+ struct rcu_head rcu_head; /* for RCU free/clear of work */
- unsigned long seen;
- atomic_t pending;
+ unsigned long seen; /* threads that have seen this work */
+ atomic_t pending; /* number of threads still to do work */
- struct super_block *sb;
- unsigned long nr_pages;
- enum writeback_sync_modes sync_mode;
+ struct wb_writeback_args args; /* writeback arguments */
- unsigned long state;
+ unsigned long state; /* flag bits, see WS_* */
};
enum {
@@ -66,22 +74,13 @@ static inline bool bdi_work_on_stack(struct bdi_work *work)
}
static inline void bdi_work_init(struct bdi_work *work,
- struct writeback_control *wbc)
+ struct wb_writeback_args *args)
{
INIT_RCU_HEAD(&work->rcu_head);
- work->sb = wbc->sb;
- work->nr_pages = wbc->nr_to_write;
- work->sync_mode = wbc->sync_mode;
+ work->args = *args;
work->state = WS_USED;
}
-static inline void bdi_work_init_on_stack(struct bdi_work *work,
- struct writeback_control *wbc)
-{
- bdi_work_init(work, wbc);
- work->state |= WS_ONSTACK;
-}
-
/**
* writeback_in_progress - determine whether there is writeback in progress
* @bdi: the device's backing_dev_info structure.
@@ -98,6 +97,11 @@ static void bdi_work_clear(struct bdi_work *work)
{
clear_bit(WS_USED_B, &work->state);
smp_mb__after_clear_bit();
+ /*
+ * work can have disappeared at this point. bit waitq functions
+ * should be able to tolerate this, provided bdi_sched_wait does
+ * not dereference it's pointer argument.
+ */
wake_up_bit(&work->state, WS_USED_B);
}
@@ -113,7 +117,8 @@ static void bdi_work_free(struct rcu_head *head)
static void wb_work_complete(struct bdi_work *work)
{
- const enum writeback_sync_modes sync_mode = work->sync_mode;
+ const enum writeback_sync_modes sync_mode = work->args.sync_mode;
+ int onstack = bdi_work_on_stack(work);
/*
* For allocated work, we can clear the done/seen bit right here.
@@ -121,9 +126,9 @@ static void wb_work_complete(struct bdi_work *work)
* to after the RCU grace period, since the stack could be invalidated
* as soon as bdi_work_clear() has done the wakeup.
*/
- if (!bdi_work_on_stack(work))
+ if (!onstack)
bdi_work_clear(work);
- if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work))
+ if (sync_mode == WB_SYNC_NONE || onstack)
call_rcu(&work->rcu_head, bdi_work_free);
}
@@ -146,21 +151,19 @@ static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
{
- if (work) {
- work->seen = bdi->wb_mask;
- BUG_ON(!work->seen);
- atomic_set(&work->pending, bdi->wb_cnt);
- BUG_ON(!bdi->wb_cnt);
-
- /*
- * Make sure stores are seen before it appears on the list
- */
- smp_mb();
+ work->seen = bdi->wb_mask;
+ BUG_ON(!work->seen);
+ atomic_set(&work->pending, bdi->wb_cnt);
+ BUG_ON(!bdi->wb_cnt);
- spin_lock(&bdi->wb_lock);
- list_add_tail_rcu(&work->list, &bdi->work_list);
- spin_unlock(&bdi->wb_lock);
- }
+ /*
+ * list_add_tail_rcu() contains the necessary barriers to
+ * make sure the above stores are seen before the item is
+ * noticed on the list
+ */
+ spin_lock(&bdi->wb_lock);
+ list_add_tail_rcu(&work->list, &bdi->work_list);
+ spin_unlock(&bdi->wb_lock);
/*
* If the default thread isn't there, make sure we add it. When
@@ -171,15 +174,7 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
else {
struct bdi_writeback *wb = &bdi->wb;
- /*
- * If we failed allocating the bdi work item, wake up the wb
- * thread always. As a safety precaution, it'll flush out
- * everything
- */
- if (!wb_has_dirty_io(wb)) {
- if (work)
- wb_clear_pending(wb, work);
- } else if (wb->task)
+ if (wb->task)
wake_up_process(wb->task);
}
}
@@ -194,48 +189,75 @@ static void bdi_wait_on_work_clear(struct bdi_work *work)
TASK_UNINTERRUPTIBLE);
}
-static struct bdi_work *bdi_alloc_work(struct writeback_control *wbc)
+static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
+ struct wb_writeback_args *args)
{
struct bdi_work *work;
+ /*
+ * This is WB_SYNC_NONE writeback, so if allocation fails just
+ * wakeup the thread for old dirty data writeback
+ */
work = kmalloc(sizeof(*work), GFP_ATOMIC);
- if (work)
- bdi_work_init(work, wbc);
+ if (work) {
+ bdi_work_init(work, args);
+ bdi_queue_work(bdi, work);
+ } else {
+ struct bdi_writeback *wb = &bdi->wb;
- return work;
+ if (wb->task)
+ wake_up_process(wb->task);
+ }
}
-void bdi_start_writeback(struct writeback_control *wbc)
+/**
+ * bdi_sync_writeback - start and wait for writeback
+ * @bdi: the backing device to write from
+ * @sb: write inodes from this super_block
+ *
+ * Description:
+ * This does WB_SYNC_ALL data integrity writeback and waits for the
+ * IO to complete. Callers must hold the sb s_umount semaphore for
+ * reading, to avoid having the super disappear before we are done.
+ */
+static void bdi_sync_writeback(struct backing_dev_info *bdi,
+ struct super_block *sb)
{
- const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
- struct bdi_work work_stack, *work = NULL;
+ struct wb_writeback_args args = {
+ .sb = sb,
+ .sync_mode = WB_SYNC_ALL,
+ .nr_pages = LONG_MAX,
+ .range_cyclic = 0,
+ };
+ struct bdi_work work;
- if (!must_wait)
- work = bdi_alloc_work(wbc);
+ bdi_work_init(&work, &args);
+ work.state |= WS_ONSTACK;
- if (!work) {
- work = &work_stack;
- bdi_work_init_on_stack(work, wbc);
- }
+ bdi_queue_work(bdi, &work);
+ bdi_wait_on_work_clear(&work);
+}
- bdi_queue_work(wbc->bdi, work);
+/**
+ * bdi_start_writeback - start writeback
+ * @bdi: the backing device to write from
+ * @nr_pages: the number of pages to write
+ *
+ * Description:
+ * This does WB_SYNC_NONE opportunistic writeback. The IO is only
+ * started when this function returns, we make no guarentees on
+ * completion. Caller need not hold sb s_umount semaphore.
+ *
+ */
+void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
+{
+ struct wb_writeback_args args = {
+ .sync_mode = WB_SYNC_NONE,
+ .nr_pages = nr_pages,
+ .range_cyclic = 1,
+ };
- /*
- * If the sync mode is WB_SYNC_ALL, block waiting for the work to
- * complete. If not, we only need to wait for the work to be started,
- * if we allocated it on-stack. We use the same mechanism, if the
- * wait bit is set in the bdi_work struct, then threads will not
- * clear pending until after they are done.
- *
- * Note that work == &work_stack if must_wait is true, so we don't
- * need to do call_rcu() here ever, since the completion path will
- * have done that for us.
- */
- if (must_wait || work == &work_stack) {
- bdi_wait_on_work_clear(work);
- if (work != &work_stack)
- call_rcu(&work->rcu_head, bdi_work_free);
- }
+ bdi_alloc_queue_work(bdi, &args);
}
/*
@@ -671,17 +693,16 @@ static inline bool over_bground_thresh(void)
* older_than_this takes precedence over nr_to_write. So we'll only write back
* all dirty pages if they are all attached to "old" mappings.
*/
-static long wb_writeback(struct bdi_writeback *wb, long nr_pages,
- struct super_block *sb,
- enum writeback_sync_modes sync_mode, int for_kupdate)
+static long wb_writeback(struct bdi_writeback *wb,
+ struct wb_writeback_args *args)
{
struct writeback_control wbc = {
.bdi = wb->bdi,
- .sb = sb,
- .sync_mode = sync_mode,
+ .sb = args->sb,
+ .sync_mode = args->sync_mode,
.older_than_this = NULL,
- .for_kupdate = for_kupdate,
- .range_cyclic = 1,
+ .for_kupdate = args->for_kupdate,
+ .range_cyclic = args->range_cyclic,
};
unsigned long oldest_jif;
long wrote = 0;
@@ -691,13 +712,18 @@ static long wb_writeback(struct bdi_writeback *wb, long nr_pages,
oldest_jif = jiffies -
msecs_to_jiffies(dirty_expire_interval * 10);
}
+ if (!wbc.range_cyclic) {
+ wbc.range_start = 0;
+ wbc.range_end = LLONG_MAX;
+ }
for (;;) {
/*
* Don't flush anything for non-integrity writeback where
* no nr_pages was given
*/
- if (!for_kupdate && nr_pages <= 0 && sync_mode == WB_SYNC_NONE)
+ if (!args->for_kupdate && args->nr_pages <= 0 &&
+ args->sync_mode == WB_SYNC_NONE)
break;
/*
@@ -705,7 +731,8 @@ static long wb_writeback(struct bdi_writeback *wb, long nr_pages,
* periodic background writeout and we are below the
* background dirty threshold, don't do anything
*/
- if (for_kupdate && nr_pages <= 0 && !over_bground_thresh())
+ if (args->for_kupdate && args->nr_pages <= 0 &&
+ !over_bground_thresh())
break;
wbc.more_io = 0;
@@ -713,7 +740,7 @@ static long wb_writeback(struct bdi_writeback *wb, long nr_pages,
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
wbc.pages_skipped = 0;
writeback_inodes_wb(wb, &wbc);
- nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+ args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
/*
@@ -731,7 +758,11 @@ static long wb_writeback(struct bdi_writeback *wb, long nr_pages,
/*
* Return the next bdi_work struct that hasn't been processed by this
- * wb thread yet
+ * wb thread yet. ->seen is initially set for each thread that exists
+ * for this device, when a thread first notices a piece of work it
+ * clears its bit. Depending on writeback type, the thread will notify
+ * completion on either receiving the work (WB_SYNC_NONE) or after
+ * it is done (WB_SYNC_ALL).
*/
static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
struct bdi_writeback *wb)
@@ -741,8 +772,9 @@ static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
rcu_read_lock();
list_for_each_entry_rcu(work, &bdi->work_list, list) {
- if (!test_and_clear_bit(wb->nr, &work->seen))
+ if (!test_bit(wb->nr, &work->seen))
continue;
+ clear_bit(wb->nr, &work->seen);
ret = work;
break;
@@ -767,8 +799,16 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
global_page_state(NR_UNSTABLE_NFS) +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
- if (nr_pages)
- return wb_writeback(wb, nr_pages, NULL, WB_SYNC_NONE, 1);
+ if (nr_pages) {
+ struct wb_writeback_args args = {
+ .nr_pages = nr_pages,
+ .sync_mode = WB_SYNC_NONE,
+ .for_kupdate = 1,
+ .range_cyclic = 1,
+ };
+
+ return wb_writeback(wb, &args);
+ }
return 0;
}
@@ -780,35 +820,31 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
{
struct backing_dev_info *bdi = wb->bdi;
struct bdi_work *work;
- long nr_pages, wrote = 0;
+ long wrote = 0;
while ((work = get_next_work_item(bdi, wb)) != NULL) {
- enum writeback_sync_modes sync_mode;
-
- nr_pages = work->nr_pages;
+ struct wb_writeback_args args = work->args;
/*
* Override sync mode, in case we must wait for completion
*/
if (force_wait)
- work->sync_mode = sync_mode = WB_SYNC_ALL;
- else
- sync_mode = work->sync_mode;
+ work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
/*
* If this isn't a data integrity operation, just notify
* that we have seen this work and we are now starting it.
*/
- if (sync_mode == WB_SYNC_NONE)
+ if (args.sync_mode == WB_SYNC_NONE)
wb_clear_pending(wb, work);
- wrote += wb_writeback(wb, nr_pages, work->sb, sync_mode, 0);
+ wrote += wb_writeback(wb, &args);
/*
* This is a data integrity writeback, so only do the
* notification when we have completed the work.
*/
- if (sync_mode == WB_SYNC_ALL)
+ if (args.sync_mode == WB_SYNC_ALL)
wb_clear_pending(wb, work);
}
@@ -849,8 +885,7 @@ int bdi_writeback_task(struct bdi_writeback *wb)
}
wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
- set_current_state(TASK_INTERRUPTIBLE);
- schedule_timeout(wait_jiffies);
+ schedule_timeout_interruptible(wait_jiffies);
try_to_freeze();
}
@@ -858,67 +893,28 @@ int bdi_writeback_task(struct bdi_writeback *wb)
}
/*
- * Schedule writeback for all backing devices. Expensive! If this is a data
- * integrity operation, writeback will be complete when this returns. If
- * we are simply called for WB_SYNC_NONE, then writeback will merely be
- * scheduled to run.
+ * Schedule writeback for all backing devices. This does WB_SYNC_NONE
+ * writeback, for integrity writeback see bdi_sync_writeback().
*/
-static void bdi_writeback_all(struct writeback_control *wbc)
+static void bdi_writeback_all(struct super_block *sb, long nr_pages)
{
- const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
+ struct wb_writeback_args args = {
+ .sb = sb,
+ .nr_pages = nr_pages,
+ .sync_mode = WB_SYNC_NONE,
+ };
struct backing_dev_info *bdi;
- struct bdi_work *work;
- LIST_HEAD(list);
-
-restart:
- spin_lock(&bdi_lock);
- list_for_each_entry(bdi, &bdi_list, bdi_list) {
- struct bdi_work *work;
+ rcu_read_lock();
+ list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
if (!bdi_has_dirty_io(bdi))
continue;
- /*
- * If work allocation fails, do the writes inline. We drop
- * the lock and restart the list writeout. This should be OK,
- * since this happens rarely and because the writeout should
- * eventually make more free memory available.
- */
- work = bdi_alloc_work(wbc);
- if (!work) {
- struct writeback_control __wbc;
-
- /*
- * Not a data integrity writeout, just continue
- */
- if (!must_wait)
- continue;
-
- spin_unlock(&bdi_lock);
- __wbc = *wbc;
- __wbc.bdi = bdi;
- writeback_inodes_wbc(&__wbc);
- goto restart;
- }
- if (must_wait)
- list_add_tail(&work->wait_list, &list);
-
- bdi_queue_work(bdi, work);
+ bdi_alloc_queue_work(bdi, &args);
}
- spin_unlock(&bdi_lock);
-
- /*
- * If this is for WB_SYNC_ALL, wait for pending work to complete
- * before returning.
- */
- while (!list_empty(&list)) {
- work = list_entry(list.next, struct bdi_work, wait_list);
- list_del(&work->wait_list);
- bdi_wait_on_work_clear(work);
- call_rcu(&work->rcu_head, bdi_work_free);
- }
+ rcu_read_unlock();
}
/*
@@ -927,17 +923,10 @@ restart:
*/
void wakeup_flusher_threads(long nr_pages)
{
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- .older_than_this = NULL,
- .range_cyclic = 1,
- };
-
if (nr_pages == 0)
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
- wbc.nr_to_write = nr_pages;
- bdi_writeback_all(&wbc);
+ bdi_writeback_all(NULL, nr_pages);
}
static noinline void block_dump___mark_inode_dirty(struct inode *inode)
@@ -1084,7 +1073,7 @@ EXPORT_SYMBOL(__mark_inode_dirty);
* on the writer throttling path, and we get decent balancing between many
* throttled threads: we don't want them all piling up on inode_sync_wait.
*/
-static void wait_sb_inodes(struct writeback_control *wbc)
+static void wait_sb_inodes(struct super_block *sb)
{
struct inode *inode, *old_inode = NULL;
@@ -1092,7 +1081,7 @@ static void wait_sb_inodes(struct writeback_control *wbc)
* We need to be protected against the filesystem going from
* r/o to r/w or vice versa.
*/
- WARN_ON(!rwsem_is_locked(&wbc->sb->s_umount));
+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
spin_lock(&inode_lock);
@@ -1103,7 +1092,7 @@ static void wait_sb_inodes(struct writeback_control *wbc)
* In which case, the inode may not be on the dirty list, but
* we still have to wait for that writeout.
*/
- list_for_each_entry(inode, &wbc->sb->s_inodes, i_sb_list) {
+ list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
struct address_space *mapping;
if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
@@ -1143,14 +1132,8 @@ static void wait_sb_inodes(struct writeback_control *wbc)
* for IO completion of submitted IO. The number of pages submitted is
* returned.
*/
-long writeback_inodes_sb(struct super_block *sb)
+void writeback_inodes_sb(struct super_block *sb)
{
- struct writeback_control wbc = {
- .sb = sb,
- .sync_mode = WB_SYNC_NONE,
- .range_start = 0,
- .range_end = LLONG_MAX,
- };
unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
long nr_to_write;
@@ -1158,9 +1141,7 @@ long writeback_inodes_sb(struct super_block *sb)
nr_to_write = nr_dirty + nr_unstable +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
- wbc.nr_to_write = nr_to_write;
- bdi_writeback_all(&wbc);
- return nr_to_write - wbc.nr_to_write;
+ bdi_writeback_all(sb, nr_to_write);
}
EXPORT_SYMBOL(writeback_inodes_sb);
@@ -1171,20 +1152,10 @@ EXPORT_SYMBOL(writeback_inodes_sb);
* This function writes and waits on any dirty inode belonging to this
* super_block. The number of pages synced is returned.
*/
-long sync_inodes_sb(struct super_block *sb)
+void sync_inodes_sb(struct super_block *sb)
{
- struct writeback_control wbc = {
- .sb = sb,
- .sync_mode = WB_SYNC_ALL,
- .range_start = 0,
- .range_end = LLONG_MAX,
- };
- long nr_to_write = LONG_MAX; /* doesn't actually matter */
-
- wbc.nr_to_write = nr_to_write;
- bdi_writeback_all(&wbc);
- wait_sb_inodes(&wbc);
- return nr_to_write - wbc.nr_to_write;
+ bdi_sync_writeback(sb->s_bdi, sb);
+ wait_sb_inodes(sb);
}
EXPORT_SYMBOL(sync_inodes_sb);