From: Omar Sandoval <osandov@xxxxxx>
Implement the swap file a_ops on Btrfs. Activation needs to make sure
that the file can be used as a swap file, which currently means it must
be fully allocated as nocow with no compression on one device. It also
sets up the swap extents directly with add_swap_extent(), so export it.
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
---
fs/btrfs/inode.c | 220 +++++++++++++++++++++++++++++++++++++++++++++++
mm/swapfile.c | 1 +
2 files changed, 221 insertions(+)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 9228cb866115..6cca8529e307 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -10526,6 +10526,224 @@ void btrfs_set_range_writeback(void *private_data, u64 start, u64 end)
}
}
+struct btrfs_swap_info {
+ u64 start;
+ u64 block_start;
+ u64 block_len;
+ u64 lowest_ppage;
+ u64 highest_ppage;
+ unsigned long nr_pages;
+ int nr_extents;
+};
+
+static int btrfs_add_swap_extent(struct swap_info_struct *sis,
+ struct btrfs_swap_info *bsi)
+{
+ unsigned long nr_pages;
+ u64 first_ppage, first_ppage_reported, next_ppage;
+ int ret;
+
+ first_ppage = ALIGN(bsi->block_start, PAGE_SIZE) >> PAGE_SHIFT;
+ next_ppage = ALIGN_DOWN(bsi->block_start + bsi->block_len,
+ PAGE_SIZE) >> PAGE_SHIFT;
+
+ if (first_ppage >= next_ppage)
+ return 0;
+ nr_pages = next_ppage - first_ppage;
+
+ first_ppage_reported = first_ppage;
+ if (bsi->start == 0)
+ first_ppage_reported++;
+ if (bsi->lowest_ppage > first_ppage_reported)
+ bsi->lowest_ppage = first_ppage_reported;
+ if (bsi->highest_ppage < (next_ppage - 1))
+ bsi->highest_ppage = next_ppage - 1;
+
+ ret = add_swap_extent(sis, bsi->nr_pages, nr_pages, first_ppage);
+ if (ret < 0)
+ return ret;
+ bsi->nr_extents += ret;
+ bsi->nr_pages += nr_pages;
+ return 0;
+}
+
+static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
+ sector_t *span)
+{
+ struct inode *inode = file_inode(file);
+ struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
+ struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+ struct extent_state *cached_state = NULL;
+ struct extent_map *em = NULL;
+ struct btrfs_device *device = NULL;
+ struct btrfs_swap_info bsi = {
+ .lowest_ppage = (sector_t)-1ULL,
+ };
+ int ret = 0;
+ u64 isize = inode->i_size;
+ u64 start;
+
+ /*
+ * The inode is locked, so these flags won't change after we check them.
+ */
+ if (BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS) {
+ btrfs_err(fs_info, "swapfile is compressed");
+ return -EINVAL;
+ }
+ if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW)) {
+ btrfs_err(fs_info, "swapfile is copy-on-write");
+ return -EINVAL;
+ }
+
+ /*
+ * Balance or device remove/replace/resize can move stuff around from
+ * under us. The EXCL_OP flag makes sure they aren't running/won't run
+ * concurrently while we are mapping the swap extents, and the fs_info
+ * nr_swapfiles counter prevents them from running while the swap file
+ * is active and moving the extents. Note that this also prevents a
+ * concurrent device add which isn't actually necessary, but it's not
+ * really worth the trouble to allow it.
+ */
+ if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags))
+ return -EBUSY;
+ atomic_inc(&fs_info->nr_swapfiles);
+ /*
+ * Snapshots can create extents which require COW even if NODATACOW is
+ * set. We use this counter to prevent snapshots. We must increment it
+ * before walking the extents because we don't want a concurrent
+ * snapshot to run after we've already checked the extents.
+ */
+ atomic_inc(&BTRFS_I(inode)->root->nr_swapfiles);
+
+ lock_extent_bits(io_tree, 0, isize - 1, &cached_state);
+ start = 0;
+ while (start < isize) {
+ u64 end, logical_block_start, physical_block_start;
+ u64 len = isize - start;
+
+ em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len, 0);
+ if (IS_ERR(em)) {
+ ret = PTR_ERR(em);
+ goto out;
+ }
+ end = extent_map_end(em);
+
+ if (em->block_start == EXTENT_MAP_HOLE) {
+ btrfs_err(fs_info, "swapfile has holes");
+ ret = -EINVAL;
+ goto out;
+ }
+ if (em->block_start == EXTENT_MAP_INLINE) {
+ /*
+ * It's unlikely we'll ever actually find ourselves
+ * here, as a file small enough to fit inline won't be
+ * big enough to store more than the swap header, but in
+ * case something changes in the future, let's catch it
+ * here rather than later.
+ */
+ btrfs_err(fs_info, "swapfile is inline");
+ ret = -EINVAL;
+ goto out;
+ }
+ if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
+ btrfs_err(fs_info, "swapfile is compressed");
+ ret = -EINVAL;
+ goto out;
+ }
+
+ logical_block_start = em->block_start + (start - em->start);
+ len = min(len, em->len - (start - em->start));
+ free_extent_map(em);
+ em = NULL;
+
+ ret = can_nocow_extent(inode, start, &len, NULL, NULL, NULL);
+ if (ret < 0) {
+ goto out;
+ } else if (ret) {
+ ret = 0;
+ } else {
+ btrfs_err(fs_info, "swapfile is copy-on-write");
+ ret = -EINVAL;
+ goto out;
+ }
+
+ em = btrfs_get_chunk_map(fs_info, logical_block_start, len);
+ if (IS_ERR(em)) {
+ ret = PTR_ERR(em);
+ goto out;
+ }
+
+ if (em->map_lookup->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
+ btrfs_err(fs_info, "swapfile data profile is not single");
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (device == NULL) {
+ device = em->map_lookup->stripes[0].dev;
+ } else if (device != em->map_lookup->stripes[0].dev) {
+ btrfs_err(fs_info, "swapfile is on multiple devices");
+ ret = -EINVAL;
+ goto out;
+ }
+
+ physical_block_start = (em->map_lookup->stripes[0].physical +
+ (logical_block_start - em->start));
+ len = min(len, em->len - (logical_block_start - em->start));
+ free_extent_map(em);
+ em = NULL;
+
+ if (bsi.block_len &&
+ bsi.block_start + bsi.block_len == physical_block_start) {
+ bsi.block_len += len;
+ } else {
+ if (bsi.block_len) {
+ ret = btrfs_add_swap_extent(sis, &bsi);
+ if (ret)
+ goto out;
+ }
+ bsi.start = start;
+ bsi.block_start = physical_block_start;
+ bsi.block_len = len;
+ }
+
+ start = end;
+ }
+
+ if (bsi.block_len)
+ ret = btrfs_add_swap_extent(sis, &bsi);
+
+out:
+ if (!IS_ERR_OR_NULL(em))
+ free_extent_map(em);
+
+ unlock_extent_cached(io_tree, 0, isize - 1, &cached_state);
+
+ clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
+
+ if (ret) {
+ atomic_dec(&BTRFS_I(inode)->root->nr_swapfiles);
+ atomic_dec(&fs_info->nr_swapfiles);
+ return ret;
+ }
+
+ if (device)
+ sis->bdev = device->bdev;
+ *span = bsi.highest_ppage - bsi.lowest_ppage + 1;
+ sis->max = bsi.nr_pages;
+ sis->pages = bsi.nr_pages - 1;
+ sis->highest_bit = bsi.nr_pages - 1;
+ return bsi.nr_extents;
+}
+
+static void btrfs_swap_deactivate(struct file *file)
+{
+ struct inode *inode = file_inode(file);
+
+ atomic_dec(&BTRFS_I(inode)->root->nr_swapfiles);
+ atomic_dec(&BTRFS_I(inode)->root->fs_info->nr_swapfiles);
+}
+
static const struct inode_operations btrfs_dir_inode_operations = {
.getattr = btrfs_getattr,
.lookup = btrfs_lookup,
@@ -10606,6 +10824,8 @@ static const struct address_space_operations btrfs_aops = {
.releasepage = btrfs_releasepage,
.set_page_dirty = btrfs_set_page_dirty,
.error_remove_page = generic_error_remove_page,
+ .swap_activate = btrfs_swap_activate,
+ .swap_deactivate = btrfs_swap_deactivate,
};
static const struct address_space_operations btrfs_symlink_aops = {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 886c9d89b144..0d934b5be05c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2382,6 +2382,7 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
list_add_tail(&new_se->list, &sis->first_swap_extent.list);
return 1;
}
+EXPORT_SYMBOL_GPL(add_swap_extent);
/*
* A `swap extent' is a simple thing which maps a contiguous range of pages
--
2.17.0
