From 7361f4d8ca65d23a18ba009b4484612183332c2f Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Mon, 7 Nov 2005 00:59:28 -0800 Subject: [PATCH] [PATCH] readahead commentary Add a few comments surrounding the generic readahead API. Also convert some ulongs into pgoff_t: the identifier for PAGE_CACHE_SIZE offsets into pagecache. Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 8 ++++---- mm/readahead.c | 31 ++++++++++++++++++++++--------- 2 files changed, 26 insertions(+), 13 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 5c1fb0a2e806..7b115feca4df 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -932,13 +932,13 @@ int write_one_page(struct page *page, int wait); * turning readahead off */ int do_page_cache_readahead(struct address_space *mapping, struct file *filp, - unsigned long offset, unsigned long nr_to_read); + pgoff_t offset, unsigned long nr_to_read); int force_page_cache_readahead(struct address_space *mapping, struct file *filp, - unsigned long offset, unsigned long nr_to_read); -unsigned long page_cache_readahead(struct address_space *mapping, + pgoff_t offset, unsigned long nr_to_read); +unsigned long page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, - unsigned long offset, + pgoff_t offset, unsigned long size); void handle_ra_miss(struct address_space *mapping, struct file_ra_state *ra, pgoff_t offset); diff --git a/mm/readahead.c b/mm/readahead.c index d0b50034e245..72e7adbb87c7 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -254,7 +254,7 @@ out: */ static int __do_page_cache_readahead(struct address_space *mapping, struct file *filp, - unsigned long offset, unsigned long nr_to_read) + pgoff_t offset, unsigned long nr_to_read) { struct inode *inode = mapping->host; struct page *page; @@ -274,7 +274,7 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp, */ read_lock_irq(&mapping->tree_lock); for (page_idx = 0; page_idx < nr_to_read; page_idx++) { - unsigned long page_offset = offset + page_idx; + pgoff_t page_offset = offset + page_idx; if (page_offset > end_index) break; @@ -311,7 +311,7 @@ out: * memory at once. */ int force_page_cache_readahead(struct address_space *mapping, struct file *filp, - unsigned long offset, unsigned long nr_to_read) + pgoff_t offset, unsigned long nr_to_read) { int ret = 0; @@ -368,7 +368,7 @@ static inline int check_ra_success(struct file_ra_state *ra, * request queues. */ int do_page_cache_readahead(struct address_space *mapping, struct file *filp, - unsigned long offset, unsigned long nr_to_read) + pgoff_t offset, unsigned long nr_to_read) { if (bdi_read_congested(mapping->backing_dev_info)) return -1; @@ -385,7 +385,7 @@ int do_page_cache_readahead(struct address_space *mapping, struct file *filp, */ static int blockable_page_cache_readahead(struct address_space *mapping, struct file *filp, - unsigned long offset, unsigned long nr_to_read, + pgoff_t offset, unsigned long nr_to_read, struct file_ra_state *ra, int block) { int actual; @@ -430,14 +430,27 @@ static int make_ahead_window(struct address_space *mapping, struct file *filp, return ret; } -/* - * page_cache_readahead is the main function. If performs the adaptive +/** + * page_cache_readahead - generic adaptive readahead + * @mapping: address_space which holds the pagecache and I/O vectors + * @ra: file_ra_state which holds the readahead state + * @filp: passed on to ->readpage() and ->readpages() + * @offset: start offset into @mapping, in PAGE_CACHE_SIZE units + * @req_size: hint: total size of the read which the caller is performing in + * PAGE_CACHE_SIZE units + * + * page_cache_readahead() is the main function. If performs the adaptive * readahead window size management and submits the readahead I/O. + * + * Note that @filp is purely used for passing on to the ->readpage[s]() + * handler: it may refer to a different file from @mapping (so we may not use + * @filp->f_mapping or @filp->f_dentry->d_inode here). + * Also, @ra may not be equal to &@filp->f_ra. + * */ unsigned long page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra, - struct file *filp, unsigned long offset, - unsigned long req_size) + struct file *filp, pgoff_t offset, unsigned long req_size) { unsigned long max, newsize; int sequential; -- 2.20.1