On Mon, 5 Oct 2015 12:29:36 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> Maybe it would be better to add the gfp_t argument to the
> address_space_operations. At a minimum, writepage(), readpage(),
> writepages(), readpages(). What a pickle.
I'm being dumb. All we need to do is to add a new
address_space_operations.readpage_gfp(..., gfp_t gfp)
etc. That should be trivial. Each fs type only has 2-4 instances of
address_space_operations so the overhead is miniscule.
As a background janitorial thing we can migrate filesystems over to the
new interface then remove address_space_operations.readpage() etc. But
this *would* add overhead: more stack and more text for no gain. So
perhaps we just leave things as they are.
That's so simple that I expect we can short-term fix this bug with that
approach. umm, something like
--- a/fs/mpage.c~a
+++ a/fs/mpage.c
@@ -139,7 +139,8 @@ map_buffer_to_page(struct page *page, st
static struct bio *
do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
sector_t *last_block_in_bio, struct buffer_head *map_bh,
- unsigned long *first_logical_block, get_block_t get_block)
+ unsigned long *first_logical_block, get_block_t get_block,
+ gfp_t gfp)
{
struct inode *inode = page->mapping->host;
const unsigned blkbits = inode->i_blkbits;
@@ -278,7 +279,7 @@ alloc_new:
}
bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
min_t(int, nr_pages, BIO_MAX_PAGES),
- GFP_KERNEL);
+ gfp);
if (bio == NULL)
goto confused;
}
@@ -310,7 +311,7 @@ confused:
}
/**
- * mpage_readpages - populate an address space with some pages & start reads against them
+ * mpage_readpages_gfp - populate an address space with some pages & start reads against them
* @mapping: the address_space
* @pages: The address of a list_head which contains the target pages. These
* pages have their ->index populated and are otherwise uninitialised.
@@ -318,6 +319,7 @@ confused:
* issued in @pages->prev to @pages->next order.
* @nr_pages: The number of pages at *@pages
* @get_block: The filesystem's block mapper function.
+ * @gfp: memory allocation constraints
*
* This function walks the pages and the blocks within each page, building and
* emitting large BIOs.
@@ -352,9 +354,8 @@ confused:
*
* This all causes the disk requests to be issued in the correct order.
*/
-int
-mpage_readpages(struct address_space *mapping, struct list_head *pages,
- unsigned nr_pages, get_block_t get_block)
+int mpage_readpages_gfp(struct address_space *mapping, struct list_head *pages,
+ unsigned nr_pages, get_block_t get_block, gfp_t gfp)
{
struct bio *bio = NULL;
unsigned page_idx;
@@ -370,12 +371,12 @@ mpage_readpages(struct address_space *ma
prefetchw(&page->flags);
list_del(&page->lru);
if (!add_to_page_cache_lru(page, mapping,
- page->index, GFP_KERNEL)) {
+ page->index, gfp)) {
bio = do_mpage_readpage(bio, page,
nr_pages - page_idx,
&last_block_in_bio, &map_bh,
&first_logical_block,
- get_block);
+ get_block, gfp);
}
page_cache_release(page);
}
@@ -384,6 +385,14 @@ mpage_readpages(struct address_space *ma
mpage_bio_submit(READ, bio);
return 0;
}
+EXPORT_SYMBOL(mpage_readpages_gfp);
+
+int mpage_readpages(struct address_space *mapping, struct list_head *pages,
+ unsigned nr_pages, get_block_t get_block)
+{
+ return mpage_readpages_gfp(mapping, pages, nr_pages, get_block,
+ GFP_KERNEL);
+}
EXPORT_SYMBOL(mpage_readpages);
/*
@@ -399,7 +408,7 @@ int mpage_readpage(struct page *page, ge
map_bh.b_state = 0;
map_bh.b_size = 0;
bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
- &map_bh, &first_logical_block, get_block);
+ &map_bh, &first_logical_block, get_block, GFP_KERNEL);
if (bio)
mpage_bio_submit(READ, bio);
return 0;
diff -puN include/linux/fs.h~a include/linux/fs.h
diff -puN include/linux/mpage.h~a include/linux/mpage.h
--- a/include/linux/mpage.h~a
+++ a/include/linux/mpage.h
@@ -15,6 +15,8 @@ struct writeback_control;
int mpage_readpages(struct address_space *mapping, struct list_head *pages,
unsigned nr_pages, get_block_t get_block);
+int mpage_readpages_gfp(struct address_space *mapping, struct list_head *pages,
+ unsigned nr_pages, get_block_t get_block, gfp_t gfp);
int mpage_readpage(struct page *page, get_block_t get_block);
int mpage_writepages(struct address_space *mapping,
struct writeback_control *wbc, get_block_t get_block);
diff -puN fs/xfs/xfs_aops.c~a fs/xfs/xfs_aops.c
--- a/fs/xfs/xfs_aops.c~a
+++ a/fs/xfs/xfs_aops.c
@@ -1908,13 +1908,14 @@ xfs_vm_readpage(
}
STATIC int
-xfs_vm_readpages(
+xfs_vm_readpages_gfp(
struct file *unused,
struct address_space *mapping,
struct list_head *pages,
unsigned nr_pages)
{
- return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);
+ return mpage_readpages_gfp(mapping, pages, nr_pages, xfs_get_blocks,
+ GFP_NOFS);
}
/*
@@ -1987,7 +1988,7 @@ xfs_vm_set_page_dirty(
const struct address_space_operations xfs_address_space_operations = {
.readpage = xfs_vm_readpage,
- .readpages = xfs_vm_readpages,
+ .readpages = xfs_vm_readpages_gfp,
.writepage = xfs_vm_writepage,
.writepages = xfs_vm_writepages,
.set_page_dirty = xfs_vm_set_page_dirty,
_
--
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