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[PATCH] splice: fix page stealing LRU handling.

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Originally from Nick Piggin, just adapted to the newer branch.

You can't check PageLRU without holding zone->lru_lock.  The page
release code can get away with it only because the page refcount is 0 at
that point. Also, you can't reliably remove pages from the LRU unless
the refcount is 0. Ever.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2006-04-02 23:11:04 +02:00
parent ad8d6f0a78
commit 3e7ee3e7b3
3 changed files with 18 additions and 19 deletions
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3
fs/pipe.c
View file

@ -95,6 +95,8 @@ static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buff
{
struct page *page = buf->page;
buf->flags &= ~PIPE_BUF_FLAG_STOLEN;
/*
* If nobody else uses this page, and we don't already have a
* temporary page, let's keep track of it as a one-deep
@ -124,6 +126,7 @@ static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer
static int anon_pipe_buf_steal(struct pipe_inode_info *info,
struct pipe_buffer *buf)
{
buf->flags |= PIPE_BUF_FLAG_STOLEN;
return 0;
}

30
fs/splice.c
View file

@ -67,16 +67,7 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
if (!remove_mapping(mapping, page))
return 1;
if (PageLRU(page)) {
struct zone *zone = page_zone(page);
spin_lock_irq(&zone->lru_lock);
BUG_ON(!PageLRU(page));
__ClearPageLRU(page);
del_page_from_lru(zone, page);
spin_unlock_irq(&zone->lru_lock);
}
buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
return 0;
}
@ -85,6 +76,7 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
{
page_cache_release(buf->page);
buf->page = NULL;
buf->flags &= ~(PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU);
}
static void *page_cache_pipe_buf_map(struct file *file,
@ -414,11 +406,12 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
{
struct file *file = sd->file;
struct address_space *mapping = file->f_mapping;
gfp_t gfp_mask = mapping_gfp_mask(mapping);
unsigned int offset;
struct page *page;
pgoff_t index;
char *src;
int ret, stolen;
int ret;
/*
* after this, page will be locked and unmapped
@ -429,7 +422,6 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
index = sd->pos >> PAGE_CACHE_SHIFT;
offset = sd->pos & ~PAGE_CACHE_MASK;
stolen = 0;
/*
* reuse buf page, if SPLICE_F_MOVE is set
@ -443,15 +435,15 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
goto find_page;
page = buf->page;
stolen = 1;
if (add_to_page_cache_lru(page, mapping, index,
mapping_gfp_mask(mapping)))
if (add_to_page_cache(page, mapping, index, gfp_mask))
goto find_page;
if (!(buf->flags & PIPE_BUF_FLAG_LRU))
lru_cache_add(page);
} else {
find_page:
ret = -ENOMEM;
page = find_or_create_page(mapping, index,
mapping_gfp_mask(mapping));
page = find_or_create_page(mapping, index, gfp_mask);
if (!page)
goto out;
@ -494,7 +486,7 @@ find_page:
} else if (ret)
goto out;
if (!stolen) {
if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
char *dst = kmap_atomic(page, KM_USER0);
memcpy(dst + offset, src + buf->offset, sd->len);
@ -511,7 +503,7 @@ find_page:
balance_dirty_pages_ratelimited(mapping);
out:
if (!stolen) {
if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
page_cache_release(page);
unlock_page(page);
}

4
include/linux/pipe_fs_i.h
View file

@ -5,10 +5,14 @@
#define PIPE_BUFFERS (16)
#define PIPE_BUF_FLAG_STOLEN 0x01
#define PIPE_BUF_FLAG_LRU 0x02
struct pipe_buffer {
struct page *page;
unsigned int offset, len;
struct pipe_buf_operations *ops;
unsigned int flags;
};
struct pipe_buf_operations {