Re: [PATCH v2 07/12] fs: clean up __mark_inode_dirty() a bit

Jan Kara
2021-01-11T15:00:27Z

On Fri 08-01-21 23:58:58, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> 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>
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> 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
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR