[PATCH 41/45] writeback: make __writeback_single_inode() cgroup writeback aware
From: Tejun Heo <tj@kernel.org>
Date: 2015-01-06 21:26:18
Also in:
linux-fsdevel, linux-mm, lkml
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
Metadata is always dirtied against the root cgroup and should thus be written out only by the root cgroup writeback. This patch updates __writeback_single_inode() so that it skips writing out metadata if the writeback is for a non-root cgroup. wbc_skip_metadata() is added to decide whether to skip metadata writeback. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> --- fs/fs-writeback.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index dbfd0b0..2bb14d5 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c@@ -684,6 +684,19 @@ static inline bool iwbl_still_has_dirty_pages(struct inode_wb_link *iwbl, return test_bit(IWBL_DIRTY_PAGES, &iwbl->data); } +/** + * wbc_skip_metadata - determine whether to skip writing out metadata + * @wbc: writeback_control in effect + * + * Called by __writeback_single_inode() to decide whether to skip writing + * out metadata. Metadata is always dirtied against the root cgroup and + * should only be written out by the root. + */ +static inline bool wbc_skip_metadata(struct writeback_control *wbc) +{ + return wbc->iwbl && !iwbl_is_root(wbc->iwbl); +} + #else /* CONFIG_CGROUP_WRITEBACK */ static void init_cgwb_dirty_page_context(struct dirty_context *dctx)
@@ -791,6 +804,11 @@ static inline bool iwbl_still_has_dirty_pages(struct inode_wb_link *iwbl, return mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY); } +static inline bool wbc_skip_metadata(struct writeback_control *wbc) +{ + return false; +} + #endif /* CONFIG_CGROUP_WRITEBACK */ /**
@@ -1128,6 +1146,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) struct address_space *mapping = inode->i_mapping; struct inode_wb_link *iwbl = inode_writeback_iwbl(inode, wbc); long nr_to_write = wbc->nr_to_write; + bool skip_metadata = wbc_skip_metadata(wbc); unsigned dirty; int ret;
@@ -1144,7 +1163,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) * separate, external IO completion path and ->sync_fs for guaranteeing * inode metadata is written back correctly. */ - if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) { + if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync && !skip_metadata) { int err = filemap_fdatawait(mapping); if (ret == 0) ret = err;
@@ -1157,8 +1176,12 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) */ spin_lock(&inode->i_lock); - dirty = inode->i_state & I_DIRTY; - inode->i_state &= ~I_DIRTY; + if (skip_metadata) + dirty = inode->i_state & I_DIRTY_PAGES; + else + dirty = inode->i_state & I_DIRTY; + + inode->i_state &= ~dirty; /* * Paired with smp_mb() in __mark_inode_dirty_dctx(). This allows
--
2.1.0
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