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mm/filemap: remove dynamically allocated array from filemap_read 

Increasing the batch size runs into diminishing returns.  It's probably
better to make, eg, three calls to filemap_get_pages() than it is to call
into kmalloc().

Link: https://lkml.kernel.org/r/20210122160140.223228-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2021-02-24 12:01:52 -08:00 committed by Linus Torvalds
parent 3a6bae4839
commit 0c7c575df5
1 changed files with 2 additions and 13 deletions
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15
mm/filemap.c
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@ -2431,8 +2431,8 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
struct file_ra_state *ra = &filp->f_ra;
struct address_space *mapping = filp->f_mapping;
struct inode *inode = mapping->host;
struct page *pages_onstack[PAGEVEC_SIZE], **pages = NULL;
unsigned int nr_pages = min_t(unsigned int, 512,
struct page *pages[PAGEVEC_SIZE];
unsigned int nr_pages = min_t(unsigned int, PAGEVEC_SIZE,
((iocb->ki_pos + iter->count + PAGE_SIZE - 1) >> PAGE_SHIFT) -
(iocb->ki_pos >> PAGE_SHIFT));
int i, pg_nr, error = 0;
@ -2446,14 +2446,6 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
if (nr_pages > ARRAY_SIZE(pages_onstack))
pages = kmalloc_array(nr_pages, sizeof(void *), GFP_KERNEL);
if (!pages) {
pages = pages_onstack;
nr_pages = min_t(unsigned int, nr_pages, ARRAY_SIZE(pages_onstack));
}
do {
cond_resched();
@ -2538,9 +2530,6 @@ put_pages:
file_accessed(filp);
if (pages != pages_onstack)
kfree(pages);
return written ? written : error;
}
EXPORT_SYMBOL_GPL(generic_file_buffered_read);