static void inode_sync_complete(struct inode *inode)
{
- /*
- * Prevent speculative execution through
- * spin_unlock(&wb->list_lock);
- */
-
+ inode->i_state &= ~I_SYNC;
+ /* Waiters must see I_SYNC cleared before being woken up */
smp_mb();
wake_up_bit(&inode->i_state, __I_SYNC);
}
}
/*
- * Wait for writeback on an inode to complete.
+ * Wait for writeback on an inode to complete. Called with i_lock held.
+ * Caller must make sure inode cannot go away when we drop i_lock.
*/
-static void inode_wait_for_writeback(struct inode *inode,
- struct bdi_writeback *wb)
+static void __inode_wait_for_writeback(struct inode *inode)
+ __releases(inode->i_lock)
+ __acquires(inode->i_lock)
{
DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
wait_queue_head_t *wqh;
wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
while (inode->i_state & I_SYNC) {
spin_unlock(&inode->i_lock);
- spin_unlock(&wb->list_lock);
__wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
- spin_lock(&wb->list_lock);
spin_lock(&inode->i_lock);
}
}
/*
- * Write out an inode's dirty pages. Called under wb->list_lock and
- * inode->i_lock. Either the caller has an active reference on the inode or
- * the inode has I_WILL_FREE set.
- *
- * If `wait' is set, wait on the writeout.
- *
- * The whole writeout design is quite complex and fragile. We want to avoid
- * starvation of particular inodes when others are being redirtied, prevent
- * livelocks, etc.
+ * Wait for writeback on an inode to complete. Caller must have inode pinned.
*/
-static int
-writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
- struct writeback_control *wbc)
+void inode_wait_for_writeback(struct inode *inode)
{
- struct address_space *mapping = inode->i_mapping;
- long nr_to_write = wbc->nr_to_write;
- unsigned dirty;
- int ret;
+ spin_lock(&inode->i_lock);
+ __inode_wait_for_writeback(inode);
+ spin_unlock(&inode->i_lock);
+}
- assert_spin_locked(&wb->list_lock);
- assert_spin_locked(&inode->i_lock);
+/*
+ * Sleep until I_SYNC is cleared. This function must be called with i_lock
+ * held and drops it. It is aimed for callers not holding any inode reference
+ * so once i_lock is dropped, inode can go away.
+ */
+static void inode_sleep_on_writeback(struct inode *inode)
+ __releases(inode->i_lock)
+{
+ DEFINE_WAIT(wait);
+ wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
+ int sleep;
- if (!atomic_read(&inode->i_count))
- WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
- else
- WARN_ON(inode->i_state & I_WILL_FREE);
+ prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
+ sleep = inode->i_state & I_SYNC;
+ spin_unlock(&inode->i_lock);
+ if (sleep)
+ schedule();
+ finish_wait(wqh, &wait);
+}
- if (inode->i_state & I_SYNC) {
+/*
+ * Find proper writeback list for the inode depending on its current state and
+ * possibly also change of its state while we were doing writeback. Here we
+ * handle things such as livelock prevention or fairness of writeback among
+ * inodes. This function can be called only by flusher thread - noone else
+ * processes all inodes in writeback lists and requeueing inodes behind flusher
+ * thread's back can have unexpected consequences.
+ */
+static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
+ struct writeback_control *wbc)
+{
+ if (inode->i_state & I_FREEING)
+ return;
+
+ /*
+ * Sync livelock prevention. Each inode is tagged and synced in one
+ * shot. If still dirty, it will be redirty_tail()'ed below. Update
+ * the dirty time to prevent enqueue and sync it again.
+ */
+ if ((inode->i_state & I_DIRTY) &&
+ (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
+ inode->dirtied_when = jiffies;
+
+ if (wbc->pages_skipped) {
/*
- * If this inode is locked for writeback and we are not doing
- * writeback-for-data-integrity, move it to b_more_io so that
- * writeback can proceed with the other inodes on s_io.
- *
- * We'll have another go at writing back this inode when we
- * completed a full scan of b_io.
+ * writeback is not making progress due to locked
+ * buffers. Skip this inode for now.
*/
- if (wbc->sync_mode != WB_SYNC_ALL) {
+ redirty_tail(inode, wb);
+ return;
+ }
+
+ if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
+ /*
+ * We didn't write back all the pages. nfs_writepages()
+ * sometimes bales out without doing anything.
+ */
+ if (wbc->nr_to_write <= 0) {
+ /* Slice used up. Queue for next turn. */
requeue_io(inode, wb);
- trace_writeback_single_inode_requeue(inode, wbc,
- nr_to_write);
- return 0;
+ } else {
+ /*
+ * Writeback blocked by something other than
+ * congestion. Delay the inode for some time to
+ * avoid spinning on the CPU (100% iowait)
+ * retrying writeback of the dirty page/inode
+ * that cannot be performed immediately.
+ */
+ redirty_tail(inode, wb);
}
-
+ } else if (inode->i_state & I_DIRTY) {
/*
- * It's a data-integrity sync. We must wait.
+ * Filesystems can dirty the inode during writeback operations,
+ * such as delayed allocation during submission or metadata
+ * updates after data IO completion.
*/
- inode_wait_for_writeback(inode, wb);
+ redirty_tail(inode, wb);
+ } else {
+ /* The inode is clean. Remove from writeback lists. */
+ list_del_init(&inode->i_wb_list);
}
+}
- BUG_ON(inode->i_state & I_SYNC);
+/*
+ * Write out an inode and its dirty pages. Do not update the writeback list
+ * linkage. That is left to the caller. The caller is also responsible for
+ * setting I_SYNC flag and calling inode_sync_complete() to clear it.
+ */
+static int
+__writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
+ struct writeback_control *wbc)
+{
+ struct address_space *mapping = inode->i_mapping;
+ long nr_to_write = wbc->nr_to_write;
+ unsigned dirty;
+ int ret;
- /* Set I_SYNC, reset I_DIRTY_PAGES */
- inode->i_state |= I_SYNC;
- inode->i_state &= ~I_DIRTY_PAGES;
- spin_unlock(&inode->i_lock);
- spin_unlock(&wb->list_lock);
+ WARN_ON(!(inode->i_state & I_SYNC));
ret = do_writepages(mapping, wbc);
* write_inode()
*/
spin_lock(&inode->i_lock);
+ /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
+ if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+ inode->i_state &= ~I_DIRTY_PAGES;
dirty = inode->i_state & I_DIRTY;
inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
spin_unlock(&inode->i_lock);
if (ret == 0)
ret = err;
}
+ trace_writeback_single_inode(inode, wbc, nr_to_write);
+ return ret;
+}
+
+/*
+ * Write out an inode's dirty pages. Either the caller has an active reference
+ * on the inode or the inode has I_WILL_FREE set.
+ *
+ * This function is designed to be called for writing back one inode which
+ * 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)
+{
+ int ret = 0;
- spin_lock(&wb->list_lock);
spin_lock(&inode->i_lock);
- inode->i_state &= ~I_SYNC;
- if (!(inode->i_state & I_FREEING)) {
+ if (!atomic_read(&inode->i_count))
+ WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
+ else
+ WARN_ON(inode->i_state & I_WILL_FREE);
+
+ if (inode->i_state & I_SYNC) {
+ if (wbc->sync_mode != WB_SYNC_ALL)
+ goto out;
/*
- * Sync livelock prevention. Each inode is tagged and synced in
- * one shot. If still dirty, it will be redirty_tail()'ed below.
- * Update the dirty time to prevent enqueue and sync it again.
+ * It's a data-integrity sync. We must wait. Since callers hold
+ * inode reference or inode has I_WILL_FREE set, it cannot go
+ * away under us.
*/
- if ((inode->i_state & I_DIRTY) &&
- (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
- inode->dirtied_when = jiffies;
-
- if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
- /*
- * We didn't write back all the pages. nfs_writepages()
- * sometimes bales out without doing anything.
- */
- inode->i_state |= I_DIRTY_PAGES;
- if (wbc->nr_to_write <= 0) {
- /*
- * slice used up: queue for next turn
- */
- requeue_io(inode, wb);
- } else {
- /*
- * Writeback blocked by something other than
- * congestion. Delay the inode for some time to
- * avoid spinning on the CPU (100% iowait)
- * retrying writeback of the dirty page/inode
- * that cannot be performed immediately.
- */
- redirty_tail(inode, wb);
- }
- } else if (inode->i_state & I_DIRTY) {
- /*
- * Filesystems can dirty the inode during writeback
- * operations, such as delayed allocation during
- * submission or metadata updates after data IO
- * completion.
- */
- redirty_tail(inode, wb);
- } else {
- /*
- * The inode is clean. At this point we either have
- * a reference to the inode or it's on it's way out.
- * No need to add it back to the LRU.
- */
- list_del_init(&inode->i_wb_list);
- }
+ __inode_wait_for_writeback(inode);
}
+ WARN_ON(inode->i_state & I_SYNC);
+ /*
+ * Skip inode if it is clean. We don't want to mess with writeback
+ * lists in this function since flusher thread may be doing for example
+ * sync in parallel and if we move the inode, it could get skipped. So
+ * here we make sure inode is on some writeback list and leave it there
+ * unless we have completely cleaned the inode.
+ */
+ if (!(inode->i_state & I_DIRTY))
+ goto out;
+ inode->i_state |= I_SYNC;
+ spin_unlock(&inode->i_lock);
+
+ ret = __writeback_single_inode(inode, wb, wbc);
+
+ spin_lock(&wb->list_lock);
+ spin_lock(&inode->i_lock);
+ /*
+ * If inode is clean, remove it from writeback lists. Otherwise don't
+ * touch it. See comment above for explanation.
+ */
+ if (!(inode->i_state & I_DIRTY))
+ list_del_init(&inode->i_wb_list);
+ spin_unlock(&wb->list_lock);
inode_sync_complete(inode);
- trace_writeback_single_inode(inode, wbc, nr_to_write);
+out:
+ spin_unlock(&inode->i_lock);
return ret;
}
redirty_tail(inode, wb);
continue;
}
- __iget(inode);
+ if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
+ /*
+ * If this inode is locked for writeback and we are not
+ * doing writeback-for-data-integrity, move it to
+ * b_more_io so that writeback can proceed with the
+ * other inodes on s_io.
+ *
+ * We'll have another go at writing back this inode
+ * when we completed a full scan of b_io.
+ */
+ spin_unlock(&inode->i_lock);
+ requeue_io(inode, wb);
+ trace_writeback_sb_inodes_requeue(inode);
+ continue;
+ }
+ spin_unlock(&wb->list_lock);
+
+ /*
+ * We already requeued the inode if it had I_SYNC set and we
+ * are doing WB_SYNC_NONE writeback. So this catches only the
+ * WB_SYNC_ALL case.
+ */
+ if (inode->i_state & I_SYNC) {
+ /* Wait for I_SYNC. This function drops i_lock... */
+ inode_sleep_on_writeback(inode);
+ /* Inode may be gone, start again */
+ continue;
+ }
+ inode->i_state |= I_SYNC;
+ spin_unlock(&inode->i_lock);
+
write_chunk = writeback_chunk_size(wb->bdi, work);
wbc.nr_to_write = write_chunk;
wbc.pages_skipped = 0;
- writeback_single_inode(inode, wb, &wbc);
+ /*
+ * We use I_SYNC to pin the inode in memory. While it is set
+ * evict_inode() will wait so the inode cannot be freed.
+ */
+ __writeback_single_inode(inode, wb, &wbc);
work->nr_pages -= write_chunk - wbc.nr_to_write;
wrote += write_chunk - wbc.nr_to_write;
+ spin_lock(&wb->list_lock);
+ spin_lock(&inode->i_lock);
if (!(inode->i_state & I_DIRTY))
wrote++;
- if (wbc.pages_skipped) {
- /*
- * writeback is not making progress due to locked
- * buffers. Skip this inode for now.
- */
- redirty_tail(inode, wb);
- }
+ requeue_inode(inode, wb, &wbc);
+ inode_sync_complete(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&wb->list_lock);
- iput(inode);
- cond_resched();
- spin_lock(&wb->list_lock);
+ cond_resched_lock(&wb->list_lock);
/*
* bail out to wb_writeback() often enough to check
* background threshold and other termination conditions.
trace_writeback_wait(wb->bdi, work);
inode = wb_inode(wb->b_more_io.prev);
spin_lock(&inode->i_lock);
- inode_wait_for_writeback(inode, wb);
- spin_unlock(&inode->i_lock);
+ spin_unlock(&wb->list_lock);
+ /* This function drops i_lock... */
+ inode_sleep_on_writeback(inode);
+ spin_lock(&wb->list_lock);
}
}
spin_unlock(&wb->list_lock);
int write_inode_now(struct inode *inode, int sync)
{
struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
- int ret;
struct writeback_control wbc = {
.nr_to_write = LONG_MAX,
.sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
wbc.nr_to_write = 0;
might_sleep();
- spin_lock(&wb->list_lock);
- spin_lock(&inode->i_lock);
- ret = writeback_single_inode(inode, wb, &wbc);
- spin_unlock(&inode->i_lock);
- spin_unlock(&wb->list_lock);
- return ret;
+ return writeback_single_inode(inode, wb, &wbc);
}
EXPORT_SYMBOL(write_inode_now);
*/
int sync_inode(struct inode *inode, struct writeback_control *wbc)
{
- struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
- int ret;
-
- spin_lock(&wb->list_lock);
- spin_lock(&inode->i_lock);
- ret = writeback_single_inode(inode, wb, wbc);
- spin_unlock(&inode->i_lock);
- spin_unlock(&wb->list_lock);
- return ret;
+ return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
}
EXPORT_SYMBOL(sync_inode);
projects / firefly-linux-kernel-4.4.55.git / blobdiff