[PATCH 4/8] zram: reorganize code layout

Sergey Senozhatsky
2015-03-03T12:49:53Z

This patch looks big, but basically it just moves code blocks forward
and backward. No functional changes.

Our current code layout looks a bit like a sandwitch.

For example,
a) between read/write handlers, we have update_used_max() helper function:

static int zram_decompress_page
static int zram_bvec_read
static inline void update_used_max
static int zram_bvec_write
static int zram_bvec_rw

b) RW request handlers __zram_make_request/zram_bio_discard are divided by
sysfs attr reset_store() function and corresponding zram_reset_device()
handler:

static void zram_bio_discard
static void zram_reset_device
static ssize_t disksize_store
static ssize_t reset_store
static void __zram_make_request

c) we first a bunch of sysfs read/store functions. then a number of
one-liners, then helper functions, RW functions, sysfs functions, helper
functions again, and so on.

Reorganize layout to be more logically grouped (a brief description,
`cat zram_drv.c | grep static` gives a bigger picture):

-- one-liners: zram_test_flag/etc.

-- helpers: is_partial_io/update_position/etc

-- sysfs attr show/store functions + ZRAM_ATTR_RO() generated stats
show() functions
exception: reset and disksize store functions are required to be after meta()
functions. because we do device create/destroy actions in these sysfs
handlers.

-- "mm" functions: meta get/put, meta alloc/free, page free
static inline bool zram_meta_get
static inline void zram_meta_put
static void zram_meta_free
static struct zram_meta *zram_meta_alloc
static void zram_free_page

-- a block of I/O functions
static int zram_decompress_page
static int zram_bvec_read
static int zram_bvec_write
static void zram_bio_discard
static int zram_bvec_rw
static void __zram_make_request
static void zram_make_request
static void zram_slot_free_notify
static int zram_rw_page

-- device contol: add/remove/init/reset functions (+zram-control class
will sit here)
static void zram_reset_device_internal
static int zram_reset_device
static ssize_t reset_store
static ssize_t disksize_store
static int zram_add
static void zram_remove
static int __init zram_init
static void __exit zram_exit

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
drivers/block/zram/zram_drv.c | 593 +++++++++++++++++++++---------------------
1 file changed, 296 insertions(+), 297 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 59662dc..bab8b20 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -63,6 +63,119 @@ static inline struct zram *dev_to_zram(struct device *dev)
return (struct zram *)dev_to_disk(dev)->private_data;
}

+/* flag operations needs meta->tb_lock */
+static int zram_test_flag(struct zram_meta *meta, u32 index,
+ enum zram_pageflags flag)
+{
+ return meta->table[index].value & BIT(flag);
+}
+
+static void zram_set_flag(struct zram_meta *meta, u32 index,
+ enum zram_pageflags flag)
+{
+ meta->table[index].value |= BIT(flag);
+}
+
+static void zram_clear_flag(struct zram_meta *meta, u32 index,
+ enum zram_pageflags flag)
+{
+ meta->table[index].value &= ~BIT(flag);
+}
+
+static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
+{
+ return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
+}
+
+static void zram_set_obj_size(struct zram_meta *meta,
+ u32 index, size_t size)
+{
+ unsigned long flags = meta->table[index].value >> ZRAM_FLAG_SHIFT;
+
+ meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
+}
+
+static inline int is_partial_io(struct bio_vec *bvec)
+{
+ return bvec->bv_len != PAGE_SIZE;
+}
+
+/*
+ * Check if request is within bounds and aligned on zram logical blocks.
+ */
+static inline int valid_io_request(struct zram *zram,
+ sector_t start, unsigned int size)
+{
+ u64 end, bound;
+
+ /* unaligned request */
+ if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
+ return 0;
+ if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
+ return 0;
+
+ end = start + (size >> SECTOR_SHIFT);
+ bound = zram->disksize >> SECTOR_SHIFT;
+ /* out of range range */
+ if (unlikely(start >= bound || end > bound || start > end))
+ return 0;
+
+ /* I/O request is valid */
+ return 1;
+}
+
+static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
+{
+ if (*offset + bvec->bv_len >= PAGE_SIZE)
+ (*index)++;
+ *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
+}
+
+static inline void update_used_max(struct zram *zram,
+ const unsigned long pages)
+{
+ unsigned long old_max, cur_max;
+
+ old_max = atomic_long_read(&zram->stats.max_used_pages);
+
+ do {
+ cur_max = old_max;
+ if (pages > cur_max)
+ old_max = atomic_long_cmpxchg(
+ &zram->stats.max_used_pages, cur_max, pages);
+ } while (old_max != cur_max);
+}
+
+static int page_zero_filled(void *ptr)
+{
+ unsigned int pos;
+ unsigned long *page;
+
+ page = (unsigned long *)ptr;
+
+ for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
+ if (page[pos])
+ return 0;
+ }
+
+ return 1;
+}
+
+static void handle_zero_page(struct bio_vec *bvec)
+{
+ struct page *page = bvec->bv_page;
+ void *user_mem;
+
+ user_mem = kmap_atomic(page);
+ if (is_partial_io(bvec))
+ memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
+ else
+ clear_page(user_mem);
+ kunmap_atomic(user_mem);
+
+ flush_dcache_page(page);
+}
+
static ssize_t disksize_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -246,65 +359,25 @@ static ssize_t comp_algorithm_store(struct device *dev,
return len;
}

-/* flag operations needs meta->tb_lock */
-static int zram_test_flag(struct zram_meta *meta, u32 index,
- enum zram_pageflags flag)
-{
- return meta->table[index].value & BIT(flag);
-}
-
-static void zram_set_flag(struct zram_meta *meta, u32 index,
- enum zram_pageflags flag)
-{
- meta->table[index].value |= BIT(flag);
-}
-
-static void zram_clear_flag(struct zram_meta *meta, u32 index,
- enum zram_pageflags flag)
-{
- meta->table[index].value &= ~BIT(flag);
-}
-
-static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
-{
- return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
-}
-
-static void zram_set_obj_size(struct zram_meta *meta,
- u32 index, size_t size)
-{
- unsigned long flags = meta->table[index].value >> ZRAM_FLAG_SHIFT;
-
- meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
-}
+ZRAM_ATTR_RO(num_reads);
+ZRAM_ATTR_RO(num_writes);
+ZRAM_ATTR_RO(failed_reads);
+ZRAM_ATTR_RO(failed_writes);
+ZRAM_ATTR_RO(invalid_io);
+ZRAM_ATTR_RO(notify_free);
+ZRAM_ATTR_RO(zero_pages);
+ZRAM_ATTR_RO(compr_data_size);

-static inline int is_partial_io(struct bio_vec *bvec)
+static inline bool zram_meta_get(struct zram *zram)
{
- return bvec->bv_len != PAGE_SIZE;
+ if (atomic_inc_not_zero(&zram->refcount))
+ return true;
+ return false;
}

-/*
- * Check if request is within bounds and aligned on zram logical blocks.
- */
-static inline int valid_io_request(struct zram *zram,
- sector_t start, unsigned int size)
+static inline void zram_meta_put(struct zram *zram)
{
- u64 end, bound;
-
- /* unaligned request */
- if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
- return 0;
- if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
- return 0;
-
- end = start + (size >> SECTOR_SHIFT);
- bound = zram->disksize >> SECTOR_SHIFT;
- /* out of range range */
- if (unlikely(start >= bound || end > bound || start > end))
- return 0;
-
- /* I/O request is valid */
- return 1;
+ atomic_dec(&zram->refcount);
}

static void zram_meta_free(struct zram_meta *meta, u64 disksize)
@@ -358,56 +431,6 @@ out_error:
return NULL;
}

-static inline bool zram_meta_get(struct zram *zram)
-{
- if (atomic_inc_not_zero(&zram->refcount))
- return true;
- return false;
-}
-
-static inline void zram_meta_put(struct zram *zram)
-{
- atomic_dec(&zram->refcount);
-}
-
-static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
-{
- if (*offset + bvec->bv_len >= PAGE_SIZE)
- (*index)++;
- *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
-}
-
-static int page_zero_filled(void *ptr)
-{
- unsigned int pos;
- unsigned long *page;
-
- page = (unsigned long *)ptr;
-
- for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
- if (page[pos])
- return 0;
- }
-
- return 1;
-}
-
-static void handle_zero_page(struct bio_vec *bvec)
-{
- struct page *page = bvec->bv_page;
- void *user_mem;
-
- user_mem = kmap_atomic(page);
- if (is_partial_io(bvec))
- memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
- else
- clear_page(user_mem);
- kunmap_atomic(user_mem);
-
- flush_dcache_page(page);
-}
-
-
/*
* To protect concurrent access to the same index entry,
* caller should hold this table index entry's bit_spinlock to
@@ -440,6 +463,7 @@ static void zram_free_page(struct zram *zram, size_t index)
zram_set_obj_size(meta, index, 0);
}

+
static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
{
int ret = 0;
@@ -525,21 +549,6 @@ out_cleanup:
return ret;
}

-static inline void update_used_max(struct zram *zram,
- const unsigned long pages)
-{
- unsigned long old_max, cur_max;
-
- old_max = atomic_long_read(&zram->stats.max_used_pages);
-
- do {
- cur_max = old_max;
- if (pages > cur_max)
- old_max = atomic_long_cmpxchg(
- &zram->stats.max_used_pages, cur_max, pages);
- } while (old_max != cur_max);
-}
-
static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
int offset)
{
@@ -667,36 +676,13 @@ out:
return ret;
}

-static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
- int offset, int rw)
-{
- int ret;
-
- if (rw == READ) {
- atomic64_inc(&zram->stats.num_reads);
- ret = zram_bvec_read(zram, bvec, index, offset);
- } else {
- atomic64_inc(&zram->stats.num_writes);
- ret = zram_bvec_write(zram, bvec, index, offset);
- }
-
- if (unlikely(ret)) {
- if (rw == READ)
- atomic64_inc(&zram->stats.failed_reads);
- else
- atomic64_inc(&zram->stats.failed_writes);
- }
-
- return ret;
-}
-
-/*
- * zram_bio_discard - handler on discard request
- * @index: physical block index in PAGE_SIZE units
- * @offset: byte offset within physical block
- */
-static void zram_bio_discard(struct zram *zram, u32 index,
- int offset, struct bio *bio)
+/*
+ * zram_bio_discard - handler on discard request
+ * @index: physical block index in PAGE_SIZE units
+ * @offset: byte offset within physical block
+ */
+static void zram_bio_discard(struct zram *zram, u32 index,
+ int offset, struct bio *bio)
{
size_t n = bio->bi_iter.bi_size;
struct zram_meta *meta = zram->meta;
@@ -729,151 +715,29 @@ static void zram_bio_discard(struct zram *zram, u32 index,
}
}

-static ssize_t disksize_store(struct device *dev,
- struct device_attribute *attr, const char *buf, size_t len)
-{
- u64 disksize;
- struct zcomp *comp;
- struct zram_meta *meta;
- struct zram *zram = dev_to_zram(dev);
- int err;
-
- disksize = memparse(buf, NULL);
- if (!disksize)
- return -EINVAL;
-
- disksize = PAGE_ALIGN(disksize);
- meta = zram_meta_alloc(zram->disk->first_minor, disksize);
- if (!meta)
- return -ENOMEM;
-
- comp = zcomp_create(zram->compressor, zram->max_comp_streams);
- if (IS_ERR(comp)) {
- pr_info("Cannot initialise %s compressing backend\n",
- zram->compressor);
- err = PTR_ERR(comp);
- goto out_free_meta;
- }
-
- down_write(&zram->init_lock);
- if (init_done(zram)) {
- pr_info("Cannot change disksize for initialized device\n");
- err = -EBUSY;
- goto out_destroy_comp;
- }
-
- init_waitqueue_head(&zram->io_done);
- atomic_set(&zram->refcount, 1);
- zram->meta = meta;
- zram->comp = comp;
- zram->disksize = disksize;
- set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
- up_write(&zram->init_lock);
-
- /*
- * Revalidate disk out of the init_lock to avoid lockdep splat.
- * It's okay because disk's capacity is protected by init_lock
- * so that revalidate_disk always sees up-to-date capacity.
- */
- revalidate_disk(zram->disk);
-
- return len;
-
-out_destroy_comp:
- up_write(&zram->init_lock);
- zcomp_destroy(comp);
-out_free_meta:
- zram_meta_free(meta, disksize);
- return err;
-}
-
-/* internal device reset part -- cleanup allocated memory and
- * return back to initial state */
-static void zram_reset_device_internal(struct zram *zram)
+static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
+ int offset, int rw)
{
- struct zram_meta *meta;
- struct zcomp *comp;
- u64 disksize;
-
- down_write(&zram->init_lock);
-
- zram->limit_pages = 0;
+ int ret;

- if (!init_done(zram)) {
- up_write(&zram->init_lock);
- return;
+ if (rw == READ) {
+ atomic64_inc(&zram->stats.num_reads);
+ ret = zram_bvec_read(zram, bvec, index, offset);
+ } else {
+ atomic64_inc(&zram->stats.num_writes);
+ ret = zram_bvec_write(zram, bvec, index, offset);
}

- meta = zram->meta;
- comp = zram->comp;
- disksize = zram->disksize;
- /*
- * Refcount will go down to 0 eventually and r/w handler
- * cannot handle further I/O so it will bail out by
- * check zram_meta_get.
- */
- zram_meta_put(zram);
- /*
- * We want to free zram_meta in process context to avoid
- * deadlock between reclaim path and any other locks.
- */
- wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
-
- /* Reset stats */
- memset(&zram->stats, 0, sizeof(zram->stats));
- zram->disksize = 0;
- zram->max_comp_streams = 1;
- set_capacity(zram->disk, 0);
-
- up_write(&zram->init_lock);
- /* I/O operation under all of CPU are done so let's free */
- zram_meta_free(meta, disksize);
- zcomp_destroy(comp);
-}
-
-static int zram_reset_device(struct zram *zram)
-{
- int ret = 0;
- struct block_device *bdev = bdget_disk(zram->disk, 0);
-
- if (!bdev)
- return -ENOMEM;
-
- mutex_lock(&bdev->bd_mutex);
- /* Do not reset an active device! */
- if (bdev->bd_openers) {
- ret = -EBUSY;
- goto out;
+ if (unlikely(ret)) {
+ if (rw == READ)
+ atomic64_inc(&zram->stats.failed_reads);
+ else
+ atomic64_inc(&zram->stats.failed_writes);
}

- /* Make sure all pending I/O is finished */
- fsync_bdev(bdev);
- zram_reset_device_internal(zram);
-out:
- mutex_unlock(&bdev->bd_mutex);
- bdput(bdev);
return ret;
}

-static ssize_t reset_store(struct device *dev,
- struct device_attribute *attr, const char *buf, size_t len)
-{
- int ret;
- unsigned short do_reset;
- struct zram *zram;
-
- zram = dev_to_zram(dev);
- ret = kstrtou16(buf, 10, &do_reset);
- if (ret)
- return ret;
-
- if (!do_reset)
- return -EINVAL;
-
- ret = zram_reset_device(zram);
- return ret ? ret : len;
-}
-
static void __zram_make_request(struct zram *zram, struct bio *bio)
{
int offset, rw;
@@ -928,9 +792,7 @@ out:
bio_io_error(bio);
}

-/*
- * Handler function for all zram I/O requests.
- */
+/* Handler function for all zram I/O requests */
static void zram_make_request(struct request_queue *queue, struct bio *bio)
{
struct zram *zram = queue->queuedata;
@@ -1010,6 +872,152 @@ out:
return err;
}

+/* internal device reset part -- cleanup allocated memory and
+ * return back to initial state */
+static void zram_reset_device_internal(struct zram *zram)
+{
+ struct zram_meta *meta;
+ struct zcomp *comp;
+ u64 disksize;
+
+ down_write(&zram->init_lock);
+
+ zram->limit_pages = 0;
+
+ if (!init_done(zram)) {
+ up_write(&zram->init_lock);
+ return;
+ }
+
+ meta = zram->meta;
+ comp = zram->comp;
+ disksize = zram->disksize;
+ /*
+ * Refcount will go down to 0 eventually and r/w handler
+ * cannot handle further I/O so it will bail out by
+ * check zram_meta_get.
+ */
+ zram_meta_put(zram);
+ /*
+ * We want to free zram_meta in process context to avoid
+ * deadlock between reclaim path and any other locks.
+ */
+ wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
+
+ /* Reset stats */
+ memset(&zram->stats, 0, sizeof(zram->stats));
+ zram->disksize = 0;
+ zram->max_comp_streams = 1;
+ set_capacity(zram->disk, 0);
+
+ up_write(&zram->init_lock);
+ /* I/O operation under all of CPU are done so let's free */
+ zram_meta_free(meta, disksize);
+ zcomp_destroy(comp);
+}
+
+static int zram_reset_device(struct zram *zram)
+{
+ int ret = 0;
+ struct block_device *bdev = bdget_disk(zram->disk, 0);
+
+ if (!bdev)
+ return -ENOMEM;
+
+ mutex_lock(&bdev->bd_mutex);
+ /* Do not reset an active device! */
+ if (bdev->bd_openers) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ /* Make sure all pending I/O is finished */
+ fsync_bdev(bdev);
+ zram_reset_device_internal(zram);
+out:
+ mutex_unlock(&bdev->bd_mutex);
+ bdput(bdev);
+ return ret;
+}
+
+static ssize_t reset_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ int ret;
+ unsigned short do_reset;
+ struct zram *zram;
+
+ zram = dev_to_zram(dev);
+ ret = kstrtou16(buf, 10, &do_reset);
+ if (ret)
+ return ret;
+
+ if (!do_reset)
+ return -EINVAL;
+
+ ret = zram_reset_device(zram);
+ return ret ? ret : len;
+}
+
+static ssize_t disksize_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ u64 disksize;
+ struct zcomp *comp;
+ struct zram_meta *meta;
+ struct zram *zram = dev_to_zram(dev);
+ int err;
+
+ disksize = memparse(buf, NULL);
+ if (!disksize)
+ return -EINVAL;
+
+ disksize = PAGE_ALIGN(disksize);
+ meta = zram_meta_alloc(zram->disk->first_minor, disksize);
+ if (!meta)
+ return -ENOMEM;
+
+ comp = zcomp_create(zram->compressor, zram->max_comp_streams);
+ if (IS_ERR(comp)) {
+ pr_info("Cannot initialise %s compressing backend\n",
+ zram->compressor);
+ err = PTR_ERR(comp);
+ goto out_free_meta;
+ }
+
+ down_write(&zram->init_lock);
+ if (init_done(zram)) {
+ pr_info("Cannot change disksize for initialized device\n");
+ err = -EBUSY;
+ goto out_destroy_comp;
+ }
+
+ init_waitqueue_head(&zram->io_done);
+ atomic_set(&zram->refcount, 1);
+ zram->meta = meta;
+ zram->comp = comp;
+ zram->disksize = disksize;
+ set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
+ up_write(&zram->init_lock);
+
+ /*
+ * Revalidate disk out of the init_lock to avoid lockdep splat.
+ * It's okay because disk's capacity is protected by init_lock
+ * so that revalidate_disk always sees up-to-date capacity.
+ */
+ revalidate_disk(zram->disk);
+
+ return len;
+
+out_destroy_comp:
+ up_write(&zram->init_lock);
+ zcomp_destroy(comp);
+out_free_meta:
+ zram_meta_free(meta, disksize);
+ return err;
+}
+
+/* per-device block device operations and sysfs attrs */
static const struct block_device_operations zram_devops = {
.swap_slot_free_notify = zram_slot_free_notify,
.rw_page = zram_rw_page,
@@ -1026,15 +1034,6 @@ static DEVICE_ATTR_RW(mem_used_max);
static DEVICE_ATTR_RW(max_comp_streams);
static DEVICE_ATTR_RW(comp_algorithm);

-ZRAM_ATTR_RO(num_reads);
-ZRAM_ATTR_RO(num_writes);
-ZRAM_ATTR_RO(failed_reads);
-ZRAM_ATTR_RO(failed_writes);
-ZRAM_ATTR_RO(invalid_io);
-ZRAM_ATTR_RO(notify_free);
-ZRAM_ATTR_RO(zero_pages);
-ZRAM_ATTR_RO(compr_data_size);
-
static struct attribute *zram_disk_attrs[] = {
&dev_attr_disksize.attr,
&dev_attr_initstate.attr,
--
2.3.1.167.g7f4ba4b