[PATCH 12/14] mm: split swap_type_of

Christoph Hellwig
2020-09-21T07:20:49Z

swap_type_of is used for two entirely different purposes:

(1) check what swap type a given device/offset corresponds to
(2) find the first available swap device that can be written to

Mixing both in a single function creates an unreadable mess. Create two
separate functions instead, and switch both to pass a dev_t instead of
a struct block_device to further simplify the code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/swap.h | 3 ++-
kernel/power/swap.c | 17 ++++++++---------
kernel/power/user.c | 16 ++++------------
mm/swapfile.c | 39 +++++++++++++++++++++------------------
4 files changed, 35 insertions(+), 40 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 661046994db4b9..4340a7b6e7a1dc 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -467,7 +467,8 @@ extern int swapcache_prepare(swp_entry_t);
extern void swap_free(swp_entry_t);
extern void swapcache_free_entries(swp_entry_t *entries, int n);
extern int free_swap_and_cache(swp_entry_t);
-extern int swap_type_of(dev_t, sector_t, struct block_device **);
+int swap_type_of(dev_t device, sector_t offset);
+int find_first_swap(dev_t *device);
extern unsigned int count_swap_pages(int, int);
extern sector_t map_swap_page(struct page *, struct block_device **);
extern sector_t swapdev_block(int, pgoff_t);
diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index 01e2858b5fe367..9d3ffbfe08dbf6 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -335,12 +335,17 @@ static int swsusp_swap_check(void)
{
int res;

- res = swap_type_of(swsusp_resume_device, swsusp_resume_block,
- &hib_resume_bdev);
+ if (swsusp_resume_device)
+ res = swap_type_of(swsusp_resume_device, swsusp_resume_block);
+ else
+ res = find_first_swap(&swsusp_resume_device);
if (res < 0)
return res;
-
root_swap = res;
+
+ hib_resume_bdev = bdget(swsusp_resume_device);
+ if (!hib_resume_bdev)
+ return -ENOMEM;
res = blkdev_get(hib_resume_bdev, FMODE_WRITE, NULL);
if (res)
return res;
@@ -349,12 +354,6 @@ static int swsusp_swap_check(void)
if (res < 0)
blkdev_put(hib_resume_bdev, FMODE_WRITE);

- /*
- * Update the resume device to the one actually used,
- * so the test_resume mode can use it in case it is
- * invoked from hibernate() to test the snapshot.
- */
- swsusp_resume_device = hib_resume_bdev->bd_dev;
return res;
}

diff --git a/kernel/power/user.c b/kernel/power/user.c
index b5815685b944fe..6510a8f7687f42 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -69,8 +69,7 @@ static int snapshot_open(struct inode *inode, struct file *filp)
memset(&data->handle, 0, sizeof(struct snapshot_handle));
if ((filp->f_flags & O_ACCMODE) == O_RDONLY) {
/* Hibernating. The image device should be accessible. */
- data->swap = swsusp_resume_device ?
- swap_type_of(swsusp_resume_device, 0, NULL) : -1;
+ data->swap = swap_type_of(swsusp_resume_device, 0);
data->mode = O_RDONLY;
data->free_bitmaps = false;
error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
@@ -210,7 +209,6 @@ struct compat_resume_swap_area {
static int snapshot_set_swap_area(struct snapshot_data *data,
void __user *argp)
{
- struct block_device *bdev;
sector_t offset;
dev_t swdev;

@@ -237,16 +235,10 @@ static int snapshot_set_swap_area(struct snapshot_data *data,
* User space encodes device types as two-byte values,
* so we need to recode them
*/
- if (!swdev) {
- data->swap = -1;
- return -EINVAL;
- }
- data->swap = swap_type_of(swdev, offset, &bdev);
+ data->swap = swap_type_of(swdev, offset);
if (data->swap < 0)
- return -ENODEV;
-
- data->dev = bdev->bd_dev;
- bdput(bdev);
+ return swdev ? -ENODEV : -EINVAL;
+ data->dev = swdev;
return 0;
}

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7438c4affc75fa..b90f8692074397 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1801,13 +1801,12 @@ int free_swap_and_cache(swp_entry_t entry)
*
* This is needed for the suspend to disk (aka swsusp).
*/
-int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
+int swap_type_of(dev_t device, sector_t offset)
{
- struct block_device *bdev = NULL;
int type;

- if (device)
- bdev = bdget(device);
+ if (!device)
+ return -1;

spin_lock(&swap_lock);
for (type = 0; type < nr_swapfiles; type++) {
@@ -1816,30 +1815,34 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
if (!(sis->flags & SWP_WRITEOK))
continue;

- if (!bdev) {
- if (bdev_p)
- *bdev_p = bdgrab(sis->bdev);
-
- spin_unlock(&swap_lock);
- return type;
- }
- if (bdev == sis->bdev) {
+ if (device == sis->bdev->bd_dev) {
struct swap_extent *se = first_se(sis);

if (se->start_block == offset) {
- if (bdev_p)
- *bdev_p = bdgrab(sis->bdev);
-
spin_unlock(&swap_lock);
- bdput(bdev);
return type;
}
}
}
spin_unlock(&swap_lock);
- if (bdev)
- bdput(bdev);
+ return -ENODEV;
+}

+int find_first_swap(dev_t *device)
+{
+ int type;
+
+ spin_lock(&swap_lock);
+ for (type = 0; type < nr_swapfiles; type++) {
+ struct swap_info_struct *sis = swap_info[type];
+
+ if (!(sis->flags & SWP_WRITEOK))
+ continue;
+ *device = sis->bdev->bd_dev;
+ spin_unlock(&swap_lock);
+ return type;
+ }
+ spin_unlock(&swap_lock);
return -ENODEV;
}

--
2.28.0