On Mon, Jul 26, 2021 at 11:46:47AM -0500, Goldwyn Rodrigues wrote:
> Simplification.
>
> file_ra_state_init() take struct address_space *, just to use inode
> pointer by dereferencing from mapping->host.
>
> The callers also derive mapping either by file->f_mapping, or
> even file->f_mapping->host->i_mapping.
>
> Change file_ra_state_init() to accept struct inode * to reduce pointer
> dereferencing, both in the callee and the caller.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
(some adjacent comments)
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index 4806295116d8..c43bf9915cda 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -351,7 +351,7 @@ static void readahead_cache(struct inode *inode)
> if (!ra)
> return;
>
> - file_ra_state_init(ra, inode->i_mapping);
> + file_ra_state_init(ra, inode);
> last_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
>
> page_cache_sync_readahead(inode->i_mapping, ra, NULL, 0, last_index);
Why does btrfs allocate a file_ra_state using kmalloc instead of
on the stack?
> +++ b/include/linux/fs.h
> @@ -3260,7 +3260,7 @@ extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
>
>
> extern void
> -file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
> +file_ra_state_init(struct file_ra_state *ra, struct inode *inode);
This should move to pagemap.h (and lose the extern).
I'd put it near the definition of VM_READAHEAD_PAGES.
> diff --git a/mm/readahead.c b/mm/readahead.c
> index d589f147f4c2..3541941df5e7 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -31,9 +31,9 @@
> * memset *ra to zero.
> */
> void
> -file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
> +file_ra_state_init(struct file_ra_state *ra, struct inode *inode)
> {
> - ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
> + ra->ra_pages = inode_to_bdi(inode)->ra_pages;
> ra->prev_pos = -1;
> }
> EXPORT_SYMBOL_GPL(file_ra_state_init);
I'm not entirely sure why this function is out-of-line, tbh.
Would it make more sense for it to be static inline in a header?
