[PATCH v3 6/7] ramfs: Convert ramfs_nommu_get_unmapped_area() to use filemap_get_folios_contig()

Vishal Moola (Oracle)
2022-08-24T00:43:06Z

Converted to use folios throughout. This is in preparation for the
removal for find_get_pages_contig(). Now also supports large folios.

The initial version of this function set the page_address to be returned
after finishing all the checks. Since folio_batches have a maximum of 15
folios, the function had to be modified to support getting and checking up
to lpages, 15 pages at a time while still returning the initial page address.
Now the function sets ret as soon as the first batch arrives, and updates it
only if a check fails.

The physical adjacency check utilizes the page frame numbers. The page frame
number of each folio must be nr_pages away from the first folio.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
---
fs/ramfs/file-nommu.c | 50 +++++++++++++++++++++++++------------------
1 file changed, 29 insertions(+), 21 deletions(-)

diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
index ba3525ccc27e..cb240eac5036 100644
--- a/fs/ramfs/file-nommu.c
+++ b/fs/ramfs/file-nommu.c
@@ -203,9 +203,9 @@ static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
- unsigned long maxpages, lpages, nr, loop, ret;
+ unsigned long maxpages, lpages, nr_folios, loop, ret, nr_pages, pfn;
struct inode *inode = file_inode(file);
- struct page **pages = NULL, **ptr, *page;
+ struct folio_batch fbatch;
loff_t isize;

/* the mapping mustn't extend beyond the EOF */
@@ -221,31 +221,39 @@ static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
goto out;

/* gang-find the pages */
- pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL);
- if (!pages)
- goto out_free;
-
- nr = find_get_pages_contig(inode->i_mapping, pgoff, lpages, pages);
- if (nr != lpages)
- goto out_free_pages; /* leave if some pages were missing */
+ folio_batch_init(&fbatch);
+ nr_pages = 0;
+repeat:
+ nr_folios = filemap_get_folios_contig(inode->i_mapping, &pgoff,
+ ULONG_MAX, &fbatch);
+ if (!nr_folios) {
+ ret = -ENOSYS;
+ return ret;
+ }

+ if (ret == -ENOSYS) {
+ ret = (unsigned long) folio_address(fbatch.folios[0]);
+ pfn = folio_pfn(fbatch.folios[0]);
+ }
/* check the pages for physical adjacency */
- ptr = pages;
- page = *ptr++;
- page++;
- for (loop = lpages; loop > 1; loop--)
- if (*ptr++ != page++)
- goto out_free_pages;
+ for (loop = 0; loop < nr_folios; loop++) {
+ if (pfn + nr_pages != folio_pfn(fbatch.folios[loop])) {
+ ret = -ENOSYS;
+ goto out_free; /* leave if not physical adjacent */
+ }
+ nr_pages += folio_nr_pages(fbatch.folios[loop]);
+ if (nr_pages >= lpages)
+ goto out_free; /* successfully found desired pages*/
+ }

+ if (nr_pages < lpages) {
+ folio_batch_release(&fbatch);
+ goto repeat; /* loop if pages are missing */
+ }
/* okay - all conditions fulfilled */
- ret = (unsigned long) page_address(pages[0]);

-out_free_pages:
- ptr = pages;
- for (loop = nr; loop > 0; loop--)
- put_page(*ptr++);
out_free:
- kfree(pages);
+ folio_batch_release(&fbatch);
out:
return ret;
}
--
2.36.1