A new addres_space_operations method is added:
int swapfile(struct address_space *, int)
When during sys_swapon() this method is found and returns no error the
swapper_space.a_ops will proxy to sis->swap_file->f_mapping->a_ops.
The swapfile method will be used to communicate to the address_space that the
VM relies on it, and the address_space should take adequate measures (like
reserving memory for mempools or the like).
Signed-off-by: Peter Zijlstra <[email protected]>
CC: Trond Myklebust <[email protected]>
---
Documentation/filesystems/Locking | 9 ++++++
include/linux/fs.h | 1
include/linux/swap.h | 3 ++
mm/Kconfig | 4 ++
mm/page_io.c | 55 ++++++++++++++++++++++++++++++++++++++
mm/swap_state.c | 5 +++
mm/swapfile.c | 22 ++++++++++++++-
7 files changed, 98 insertions(+), 1 deletion(-)
Index: linux-2.6-git/include/linux/swap.h
===================================================================
--- linux-2.6-git.orig/include/linux/swap.h 2007-03-26 13:40:38.000000000 +0200
+++ linux-2.6-git/include/linux/swap.h 2007-03-26 13:40:43.000000000 +0200
@@ -163,6 +163,7 @@ enum {
SWP_USED = (1 << 0), /* is slot in swap_info[] used? */
SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */
SWP_ACTIVE = (SWP_USED | SWP_WRITEOK),
+ SWP_FILE = (1 << 2), /* file swap area */
/* add others here before... */
SWP_SCANNING = (1 << 8), /* refcount in scan_swap_map */
};
@@ -264,6 +265,8 @@ extern void swap_unplug_io_fn(struct bac
/* linux/mm/page_io.c */
extern int swap_readpage(struct file *, struct page *);
extern int swap_writepage(struct page *page, struct writeback_control *wbc);
+extern void swap_sync_page(struct page *page);
+extern int swap_set_page_dirty(struct page *page);
extern int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err);
/* linux/mm/swap_state.c */
Index: linux-2.6-git/mm/page_io.c
===================================================================
--- linux-2.6-git.orig/mm/page_io.c 2007-03-26 13:34:51.000000000 +0200
+++ linux-2.6-git/mm/page_io.c 2007-03-26 13:40:43.000000000 +0200
@@ -17,6 +17,7 @@
#include <linux/bio.h>
#include <linux/swapops.h>
#include <linux/writeback.h>
+#include <linux/buffer_head.h>
#include <asm/pgtable.h>
static struct bio *get_swap_bio(gfp_t gfp_flags, pgoff_t index,
@@ -110,6 +111,18 @@ int swap_writepage(struct page *page, st
unlock_page(page);
goto out;
}
+#ifdef CONFIG_SWAP_FILE
+ {
+ struct swap_info_struct *sis = page_swap_info(page);
+ if (sis->flags & SWP_FILE) {
+ ret = sis->swap_file->f_mapping->
+ a_ops->writepage(page, wbc);
+ if (!ret)
+ count_vm_event(PSWPOUT);
+ return ret;
+ }
+ }
+#endif
bio = get_swap_bio(GFP_NOIO, page_private(page), page,
end_swap_bio_write);
if (bio == NULL) {
@@ -128,6 +141,36 @@ out:
return ret;
}
+#ifdef CONFIG_SWAP_FILE
+void swap_sync_page(struct page *page)
+{
+ struct swap_info_struct *sis = page_swap_info(page);
+
+ if (sis->flags & SWP_FILE) {
+ const struct address_space_operations * a_ops =
+ sis->swap_file->f_mapping->a_ops;
+ if (a_ops->sync_page)
+ a_ops->sync_page(page);
+ } else
+ block_sync_page(page);
+}
+
+int swap_set_page_dirty(struct page *page)
+{
+ struct swap_info_struct *sis = page_swap_info(page);
+
+ if (sis->flags & SWP_FILE) {
+ const struct address_space_operations * a_ops =
+ sis->swap_file->f_mapping->a_ops;
+ if (a_ops->set_page_dirty)
+ return a_ops->set_page_dirty(page);
+ return __set_page_dirty_buffers(page);
+ }
+
+ return __set_page_dirty_nobuffers(page);
+}
+#endif
+
int swap_readpage(struct file *file, struct page *page)
{
struct bio *bio;
@@ -135,6 +178,18 @@ int swap_readpage(struct file *file, str
BUG_ON(!PageLocked(page));
ClearPageUptodate(page);
+#ifdef CONFIG_SWAP_FILE
+ {
+ struct swap_info_struct *sis = page_swap_info(page);
+ if (sis->flags & SWP_FILE) {
+ ret = sis->swap_file->f_mapping->
+ a_ops->readpage(sis->swap_file, page);
+ if (!ret)
+ count_vm_event(PSWPIN);
+ return ret;
+ }
+ }
+#endif
bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
end_swap_bio_read);
if (bio == NULL) {
Index: linux-2.6-git/mm/swap_state.c
===================================================================
--- linux-2.6-git.orig/mm/swap_state.c 2007-03-26 13:34:51.000000000 +0200
+++ linux-2.6-git/mm/swap_state.c 2007-03-26 13:40:43.000000000 +0200
@@ -26,8 +26,13 @@
*/
static const struct address_space_operations swap_aops = {
.writepage = swap_writepage,
+#ifdef CONFIG_SWAP_FILE
+ .sync_page = swap_sync_page,
+ .set_page_dirty = swap_set_page_dirty,
+#else
.sync_page = block_sync_page,
.set_page_dirty = __set_page_dirty_nobuffers,
+#endif
.migratepage = migrate_page,
};
Index: linux-2.6-git/mm/swapfile.c
===================================================================
--- linux-2.6-git.orig/mm/swapfile.c 2007-03-26 13:40:38.000000000 +0200
+++ linux-2.6-git/mm/swapfile.c 2007-03-26 13:40:43.000000000 +0200
@@ -981,6 +981,13 @@ static void destroy_swap_extents(struct
list_del(&se->list);
kfree(se);
}
+#ifdef CONFIG_SWAP_FILE
+ if (sis->flags & SWP_FILE) {
+ sis->flags &= ~SWP_FILE;
+ sis->swap_file->f_mapping->a_ops->
+ swapfile(sis->swap_file->f_mapping, 0);
+ }
+#endif
}
/*
@@ -1073,6 +1080,19 @@ static int setup_swap_extents(struct swa
goto done;
}
+#ifdef CONFIG_SWAP_FILE
+ if (sis->swap_file->f_mapping->a_ops->swapfile) {
+ ret = sis->swap_file->f_mapping->a_ops->
+ swapfile(sis->swap_file->f_mapping, 1);
+ if (!ret) {
+ sis->flags |= SWP_FILE;
+ ret = add_swap_extent(sis, 0, sis->max, 0);
+ *span = sis->pages;
+ }
+ goto done;
+ }
+#endif
+
blkbits = inode->i_blkbits;
blocks_per_page = PAGE_SIZE >> blkbits;
@@ -1640,7 +1660,7 @@ asmlinkage long sys_swapon(const char __
mutex_lock(&swapon_mutex);
spin_lock(&swap_lock);
- p->flags = SWP_ACTIVE;
+ p->flags |= SWP_WRITEOK;
nr_swap_pages += nr_good_pages;
total_swap_pages += nr_good_pages;
Index: linux-2.6-git/include/linux/fs.h
===================================================================
--- linux-2.6-git.orig/include/linux/fs.h 2007-03-26 13:34:51.000000000 +0200
+++ linux-2.6-git/include/linux/fs.h 2007-03-26 13:40:43.000000000 +0200
@@ -428,6 +428,7 @@ struct address_space_operations {
int (*migratepage) (struct address_space *,
struct page *, struct page *);
int (*launder_page) (struct page *);
+ int (*swapfile)(struct address_space *, int);
};
struct backing_dev_info;
Index: linux-2.6-git/Documentation/filesystems/Locking
===================================================================
--- linux-2.6-git.orig/Documentation/filesystems/Locking 2007-03-26 13:34:51.000000000 +0200
+++ linux-2.6-git/Documentation/filesystems/Locking 2007-03-26 13:40:43.000000000 +0200
@@ -172,6 +172,7 @@ prototypes:
int (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
loff_t offset, unsigned long nr_segs);
int (*launder_page) (struct page *);
+ int (*swapfile) (struct address_space *, int);
locking rules:
All except set_page_dirty may block
@@ -190,6 +191,7 @@ invalidatepage: no yes
releasepage: no yes
direct_IO: no
launder_page: no yes
+swapfile no
->prepare_write(), ->commit_write(), ->sync_page() and ->readpage()
may be called from the request handler (/dev/loop).
@@ -289,6 +291,13 @@ cleaned, or an error value if not. Note
getting mapped back in and redirtied, it needs to be kept locked
across the entire operation.
+ ->swapfile() will be called with a non zero argument on address spaces
+backing non block device backed swapfiles. A return value of zero indicates
+success. In which case this address space can be used for backing swapspace.
+The swapspace operations will be proxied to the address space operations.
+Swapoff will call this method with a zero argument to release the address
+space.
+
Note: currently almost all instances of address_space methods are
using BKL for internal serialization and that's one of the worst sources
of contention. Normally they are calling library functions (in fs/buffer.c)
Index: linux-2.6-git/mm/Kconfig
===================================================================
--- linux-2.6-git.orig/mm/Kconfig 2007-03-26 13:36:32.000000000 +0200
+++ linux-2.6-git/mm/Kconfig 2007-03-26 13:41:22.000000000 +0200
@@ -166,3 +166,6 @@ config ZONE_DMA_FLAG
config SLAB_FAIR
def_bool n
depends on SLAB
+
+config SWAP_FILE
+ def_bool n
--
-
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