From 0b1efc3e78d12278a8c0f2c665d66564a2cb965f Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 25 Jun 2024 12:18:57 +0200 Subject: readahead: drop dead code in ondemand_readahead() ondemand_readahead() scales up the readahead window if the current read would hit the readahead mark placed by itself. However the condition is mostly dead code because: a) In case of async readahead we always increase ra->start so ra->start == index is never true. b) In case of sync readahead we either go through try_context_readahead() in which case ra->async_size == 1 < ra->size or we go through initial_readahead where ra->async_size == ra->size iff ra->size == max_pages. So the only practical effect is reducing async_size for large initial reads. Make the code more obvious. Link: https://lkml.kernel.org/r/20240625101909.12234-7-jack@suse.cz Signed-off-by: Jan Kara Reviewed-by: Josef Bacik Tested-by: Zhang Peng Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/readahead.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-) (limited to 'mm') diff --git a/mm/readahead.c b/mm/readahead.c index 9ea5125a0dce..d92a5e8d89c4 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -549,7 +549,6 @@ static void ondemand_readahead(struct readahead_control *ractl, struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host); struct file_ra_state *ra = ractl->ra; unsigned long max_pages = ra->ra_pages; - unsigned long add_pages; pgoff_t index = readahead_index(ractl); pgoff_t expected, prev_index; unsigned int order = folio ? folio_order(folio) : 0; @@ -638,26 +637,10 @@ static void ondemand_readahead(struct readahead_control *ractl, initial_readahead: ra->start = index; ra->size = get_init_ra_size(req_size, max_pages); - ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size; + ra->async_size = ra->size > req_size ? ra->size - req_size : + ra->size >> 1; readit: - /* - * Will this read hit the readahead marker made by itself? - * If so, trigger the readahead marker hit now, and merge - * the resulted next readahead window into the current one. - * Take care of maximum IO pages as above. - */ - if (index == ra->start && ra->size == ra->async_size) { - add_pages = get_next_ra_size(ra, max_pages); - if (ra->size + add_pages <= max_pages) { - ra->async_size = add_pages; - ra->size += add_pages; - } else { - ra->size = max_pages; - ra->async_size = max_pages >> 1; - } - } - ractl->_index = ra->start; page_cache_ra_order(ractl, ra, order); } -- cgit v1.2.3