writeback: fix writeback_inodes_wb from writeback_inodes_sb
When we call writeback_inodes_wb from writeback_inodes_sb we always have
s_umount held, which currently makes the whole operation a no-op.
But if we are called to write out inodes for a specific superblock we always
have s_umount held, so replace the incorrect logic checking for WB_SYNC_ALL
which only worked by coincidence with the proper check for an explicit
superblock argument.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 2627f0d..68ece4b 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -518,39 +518,19 @@
return ret;
}
-static void unpin_sb_for_writeback(struct super_block *sb)
-{
- up_read(&sb->s_umount);
- put_super(sb);
-}
-
-enum sb_pin_state {
- SB_PINNED,
- SB_NOT_PINNED,
- SB_PIN_FAILED
-};
-
/*
- * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
+ * For background writeback the caller does not have the sb pinned
* before calling writeback. So make sure that we do pin it, so it doesn't
* go away while we are writing inodes from it.
*/
-static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
- struct super_block *sb)
+static bool pin_sb_for_writeback(struct super_block *sb)
{
- /*
- * Caller must already hold the ref for this
- */
- if (wbc->sync_mode == WB_SYNC_ALL) {
- WARN_ON(!rwsem_is_locked(&sb->s_umount));
- return SB_NOT_PINNED;
- }
spin_lock(&sb_lock);
sb->s_count++;
if (down_read_trylock(&sb->s_umount)) {
if (sb->s_root) {
spin_unlock(&sb_lock);
- return SB_PINNED;
+ return true;
}
/*
* umounted, drop rwsem again and fall through to failure
@@ -559,7 +539,7 @@
}
sb->s_count--;
spin_unlock(&sb_lock);
- return SB_PIN_FAILED;
+ return false;
}
/*
@@ -638,24 +618,29 @@
struct inode *inode = list_entry(wb->b_io.prev,
struct inode, i_list);
struct super_block *sb = inode->i_sb;
- enum sb_pin_state state;
- if (wbc->sb && sb != wbc->sb) {
- /* super block given and doesn't
- match, skip this inode */
- redirty_tail(inode);
- continue;
+ if (wbc->sb) {
+ /*
+ * We are requested to write out inodes for a specific
+ * superblock. This means we already have s_umount
+ * taken by the caller which also waits for us to
+ * complete the writeout.
+ */
+ if (sb != wbc->sb) {
+ redirty_tail(inode);
+ continue;
+ }
+
+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
+ ret = writeback_sb_inodes(sb, wb, wbc);
+ } else {
+ if (!pin_sb_for_writeback(sb))
+ continue;
+ ret = writeback_sb_inodes(sb, wb, wbc);
+ drop_super(sb);
}
- state = pin_sb_for_writeback(wbc, sb);
- if (state == SB_PIN_FAILED) {
- requeue_io(inode);
- continue;
- }
- ret = writeback_sb_inodes(sb, wb, wbc);
-
- if (state == SB_PINNED)
- unpin_sb_for_writeback(sb);
if (ret)
break;
}