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 CC: Trond Myklebust --- Documentation/filesystems/Locking | 9 ++++++++ include/linux/fs.h | 1 include/linux/swap.h | 3 ++ mm/Kconfig | 4 +++ mm/page_io.c | 42 ++++++++++++++++++++++++++++++++++++++ mm/swap_state.c | 4 +++ mm/swapfile.c | 22 +++++++++++++++++++ 7 files changed, 84 insertions(+), 1 deletion(-) Index: linux-2.6/include/linux/swap.h =================================================================== --- linux-2.6.orig/include/linux/swap.h +++ linux-2.6/include/linux/swap.h @@ -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 */ }; @@ -265,6 +266,8 @@ extern int shmem_unuse(swp_entry_t entry /* 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/mm/page_io.c =================================================================== --- linux-2.6.orig/mm/page_io.c +++ linux-2.6/mm/page_io.c @@ -17,6 +17,7 @@ #include #include #include +#include #include 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 +141,23 @@ out: return ret; } +#ifdef CONFIG_SWAP_FILE +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 +165,18 @@ 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/mm/swap_state.c =================================================================== --- linux-2.6.orig/mm/swap_state.c +++ linux-2.6/mm/swap_state.c @@ -26,7 +26,11 @@ */ static const struct address_space_operations swap_aops = { .writepage = swap_writepage, +#ifdef CONFIG_SWAP_FILE + .set_page_dirty = swap_set_page_dirty, +#else .set_page_dirty = __set_page_dirty_nobuffers, +#endif .migratepage = migrate_page, }; Index: linux-2.6/mm/swapfile.c =================================================================== --- linux-2.6.orig/mm/swapfile.c +++ linux-2.6/mm/swapfile.c @@ -948,6 +948,13 @@ 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 } /* @@ -1040,6 +1047,19 @@ 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; @@ -1603,7 +1623,7 @@ 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/include/linux/fs.h =================================================================== --- linux-2.6.orig/include/linux/fs.h +++ linux-2.6/include/linux/fs.h @@ -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/Documentation/filesystems/Locking =================================================================== --- linux-2.6.orig/Documentation/filesystems/Locking +++ linux-2.6/Documentation/filesystems/Locking @@ -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/mm/Kconfig =================================================================== --- linux-2.6.orig/mm/Kconfig +++ linux-2.6/mm/Kconfig @@ -165,6 +165,9 @@ config ZONE_DMA_FLAG config SLAB_FAIR def_bool n + +config SWAP_FILE + def_bool n # # Adaptive file readahead # -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/