diff options
Diffstat (limited to 'fs/fs-writeback.c')
| -rw-r--r-- | fs/fs-writeback.c | 57 |
1 files changed, 33 insertions, 24 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index cee1df6e3bd4..e91980f49388 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1442,9 +1442,15 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, } /* - * 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. + * Write out an inode and its dirty pages (or some of its dirty pages, depending + * on @wbc->nr_to_write), and clear the relevant dirty flags from i_state. + * + * This doesn't remove the inode from the writeback list it is on, except + * potentially to move it from b_dirty_time to b_dirty due to timestamp + * expiration. The caller is otherwise responsible for writeback list handling. + * + * The caller is also responsible for setting the I_SYNC flag beforehand and + * calling inode_sync_complete() to clear it afterwards. */ static int __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) @@ -1487,9 +1493,10 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) } /* - * Some filesystems may redirty the inode during the writeback - * due to delalloc, clear dirty metadata flags right before - * write_inode() + * Get and clear the dirty flags from i_state. This needs to be done + * after calling writepages because some filesystems may redirty the + * inode during writepages due to delalloc. It also needs to be done + * after handling timestamp expiration, as that may dirty the inode too. */ spin_lock(&inode->i_lock); dirty = inode->i_state & I_DIRTY; @@ -1524,12 +1531,13 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) } /* - * 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. + * Write out an inode's dirty data and metadata on-demand, i.e. separately from + * the regular batched writeback done by the flusher threads in + * writeback_sb_inodes(). @wbc controls various aspects of the write, such as + * whether it is a data-integrity sync (%WB_SYNC_ALL) or not (%WB_SYNC_NONE). * - * 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(). + * To prevent the inode from going away, either the caller must have a reference + * to the inode, or the inode must have I_WILL_FREE or I_FREEING set. */ static int writeback_single_inode(struct inode *inode, struct writeback_control *wbc) @@ -1544,23 +1552,23 @@ static int writeback_single_inode(struct inode *inode, WARN_ON(inode->i_state & I_WILL_FREE); if (inode->i_state & I_SYNC) { - if (wbc->sync_mode != WB_SYNC_ALL) - goto out; /* - * 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. + * Writeback is already running on the inode. For WB_SYNC_NONE, + * that's enough and we can just return. For WB_SYNC_ALL, we + * must wait for the existing writeback to complete, then do + * writeback again if there's anything left. */ + if (wbc->sync_mode != WB_SYNC_ALL) + goto out; __inode_wait_for_writeback(inode); } WARN_ON(inode->i_state & I_SYNC); /* - * Skip inode if it is clean and we have no outstanding writeback in - * WB_SYNC_ALL mode. 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 the inode is already fully clean, then there's nothing to do. + * + * For data-integrity syncs we also need to check whether any pages are + * still under writeback, e.g. due to prior WB_SYNC_NONE writeback. If + * there are any such pages, we'll need to wait for them. */ if (!(inode->i_state & I_DIRTY_ALL) && (wbc->sync_mode != WB_SYNC_ALL || @@ -1576,8 +1584,9 @@ static int writeback_single_inode(struct inode *inode, wb = inode_to_wb_and_lock_list(inode); 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 the inode is now fully clean, then it can be safely removed from + * its writeback list (if any). Otherwise the flusher threads are + * responsible for the writeback lists. */ if (!(inode->i_state & I_DIRTY_ALL)) inode_io_list_del_locked(inode, wb); |