int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
pgoff_t offset, unsigned long nr_to_read)
{
- int ret = 0;
-
if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages))
return -EINVAL;
this_chunk = nr_to_read;
err = __do_page_cache_readahead(mapping, filp,
offset, this_chunk, 0);
- if (err < 0) {
- ret = err;
- break;
- }
- ret += err;
+ if (err < 0)
+ return err;
+
offset += this_chunk;
nr_to_read -= this_chunk;
}
- return ret;
+ return 0;
}
/*
unsigned long req_size)
{
unsigned long max = max_sane_readahead(ra->ra_pages);
+ pgoff_t prev_offset;
/*
* start of file
/*
* sequential cache miss
+ * trivial case: (offset - prev_offset) == 1
+ * unaligned reads: (offset - prev_offset) == 0
*/
- if (offset - (ra->prev_pos >> PAGE_CACHE_SHIFT) <= 1UL)
+ prev_offset = (unsigned long long)ra->prev_pos >> PAGE_CACHE_SHIFT;
+ if (offset - prev_offset <= 1UL)
goto initial_readahead;
/*
do_readahead(struct address_space *mapping, struct file *filp,
pgoff_t index, unsigned long nr)
{
- if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
+ if (!mapping || !mapping->a_ops)
return -EINVAL;
- force_page_cache_readahead(mapping, filp, index, nr);
- return 0;
+ return force_page_cache_readahead(mapping, filp, index, nr);
}
SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count)