[PATCH v3 07/11] fs: clean up __mark_inode_dirty() a bit

Eric Biggers
2021-01-12T19:05:34Z

Improve some comments, and don't bother checking for the I_DIRTY_TIME
flag in the case where we just cleared it.

Also, warn if I_DIRTY_TIME and I_DIRTY_PAGES are passed to
__mark_inode_dirty() at the same time, as this case isn't handled.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/fs-writeback.c | 49 +++++++++++++++++++++++++++++------------------
1 file changed, 30 insertions(+), 19 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 2e6064012f7d3..80ee9816d9df5 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2219,23 +2219,24 @@ static noinline void block_dump___mark_inode_dirty(struct inode *inode)
}

/**
- * __mark_inode_dirty - internal function
+ * __mark_inode_dirty - internal function to mark an inode dirty
*
* @inode: inode to mark
- * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
+ * @flags: what kind of dirty, e.g. I_DIRTY_SYNC. This can be a combination of
+ * multiple I_DIRTY_* flags, except that I_DIRTY_TIME can't be combined
+ * with I_DIRTY_PAGES.
*
- * Mark an inode as dirty. Callers should use mark_inode_dirty or
- * mark_inode_dirty_sync.
+ * Mark an inode as dirty. We notify the filesystem, then update the inode's
+ * dirty flags. Then, if needed we add the inode to the appropriate dirty list.
*
- * Put the inode on the super block's dirty list.
+ * Most callers should use mark_inode_dirty() or mark_inode_dirty_sync()
+ * instead of calling this directly.
*
- * CAREFUL! We mark it dirty unconditionally, but move it onto the
- * dirty list only if it is hashed or if it refers to a blockdev.
- * If it was not hashed, it will never be added to the dirty list
- * even if it is later hashed, as it will have been marked dirty already.
+ * CAREFUL! We only add the inode to the dirty list if it is hashed or if it
+ * refers to a blockdev. Unhashed inodes will never be added to the dirty list
+ * even if they are later hashed, as they will have been marked dirty already.
*
- * In short, make sure you hash any inodes _before_ you start marking
- * them dirty.
+ * In short, ensure you hash any inodes _before_ you start marking them dirty.
*
* Note that for blockdevs, inode->dirtied_when represents the dirtying time of
* the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
@@ -2247,25 +2248,34 @@ static noinline void block_dump___mark_inode_dirty(struct inode *inode)
void __mark_inode_dirty(struct inode *inode, int flags)
{
struct super_block *sb = inode->i_sb;
- int dirtytime;
+ int dirtytime = 0;

trace_writeback_mark_inode_dirty(inode, flags);

- /*
- * Don't do this for I_DIRTY_PAGES - that doesn't actually
- * dirty the inode itself
- */
if (flags & I_DIRTY_INODE) {
+ /*
+ * Notify the filesystem about the inode being dirtied, so that
+ * (if needed) it can update on-disk fields and journal the
+ * inode. This is only needed when the inode itself is being
+ * dirtied now. I.e. it's only needed for I_DIRTY_INODE, not
+ * for just I_DIRTY_PAGES or I_DIRTY_TIME.
+ */
trace_writeback_dirty_inode_start(inode, flags);
-
if (sb->s_op->dirty_inode)
sb->s_op->dirty_inode(inode, flags & I_DIRTY_INODE);
-
trace_writeback_dirty_inode(inode, flags);

+ /* I_DIRTY_INODE supersedes I_DIRTY_TIME. */
flags &= ~I_DIRTY_TIME;
+ } else {
+ /*
+ * Else it's either I_DIRTY_PAGES, I_DIRTY_TIME, or nothing.
+ * (We don't support setting both I_DIRTY_PAGES and I_DIRTY_TIME
+ * in one call to __mark_inode_dirty().)
+ */
+ dirtytime = flags & I_DIRTY_TIME;
+ WARN_ON_ONCE(dirtytime && flags != I_DIRTY_TIME);
}
- dirtytime = flags & I_DIRTY_TIME;

/*
* Paired with smp_mb() in __writeback_single_inode() for the
@@ -2288,6 +2298,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)

inode_attach_wb(inode, NULL);

+ /* I_DIRTY_INODE supersedes I_DIRTY_TIME. */
if (flags & I_DIRTY_INODE)
inode->i_state &= ~I_DIRTY_TIME;
inode->i_state |= flags;
--
2.30.0