Since dm-log-writes will record all writes, include data and metadata
writes, it can consume a lot of space.
However for a lot of filesystems, the data bio (without METADATA flag)
can be skipped for certain use case, thus we can skip them in
dm-log-writes to hugely reduce space usage.
This patch will introduce a new optional constructor parameter,
"dump_type=%s", for dm-log-writes.
The '%s' can be ALL, METADATA, FUA, FLUSH, DISCARD, MARK or the ORed
result of them.
The default dump_type will be 'ALL', so the behavior is not changed at
all.
But user can specify dump_type=METADATA|FUA|FLUSH|DISCARD|MARK to skip
data writes to save space on log device.
Currently the dump_type can only be speicified at contruction time.
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
drivers/md/dm-log-writes.c | 146 +++++++++++++++++++++++++++++++++++--
1 file changed, 141 insertions(+), 5 deletions(-)
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index af94bbe77ce2..9edf0bdcae39 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -115,6 +115,7 @@ struct log_writes_c {
struct list_head logging_blocks;
wait_queue_head_t wait;
struct task_struct *log_kthread;
+ u32 dump_type;
};
struct pending_block {
@@ -503,15 +504,99 @@ static int log_writes_kthread(void *arg)
return 0;
}
+#define string_type_to_bit(string) \
+({ \
+ if (!strcasecmp(p, #string)) { \
+ dump_type |= LOG_##string##_FLAG; \
+ continue; \
+ } \
+})
+static int parse_dump_types(struct log_writes_c *lc, const char *string)
+{
+ char *orig;
+ char *opts;
+ char *p;
+ u32 dump_type = LOG_MARK_FLAG;
+ int ret = 0;
+
+ opts = kstrdup(string, GFP_KERNEL);
+ if (!opts)
+ return -ENOMEM;
+ orig = opts;
+
+ while ((p = strsep(&opts, "|")) != NULL) {
+ if (!*p)
+ continue;
+ if (!strcasecmp(p, "ALL")) {
+ dump_type = (u32)-1;
+ /* No need to check other flags */
+ break;
+ }
+ string_type_to_bit(METADATA);
+ string_type_to_bit(FUA);
+ string_type_to_bit(FLUSH);
+ string_type_to_bit(DISCARD);
+ string_type_to_bit(MARK);
+ ret = -EINVAL;
+ goto out;
+ }
+out:
+ kfree(orig);
+ if (!ret)
+ lc->dump_type = dump_type;
+ return ret;
+}
+#undef string_type_to_bit
+
+/* Must be large enough to contain "METADATA|FUA|FLUSH|DISCARD|MARK" */
+#define DUMP_TYPES_BUF_SIZE 256
+#define dump_type_to_string(name) \
+({ \
+ if (lc->dump_type & LOG_##name##_FLAG) { \
+ if (!first_word) \
+ strcat(buf, "|"); \
+ strcat(buf, #name); \
+ first_word = false; \
+ } \
+ })
+static void status_dump_types(struct log_writes_c *lc, char *buf)
+{
+ bool first_word = true;
+
+ buf[0] = '\0';
+
+ if (lc->dump_type == (u32)-1) {
+ strcat(buf, "ALL");
+ return;
+ }
+ dump_type_to_string(METADATA);
+ dump_type_to_string(FUA);
+ dump_type_to_string(FLUSH);
+ dump_type_to_string(DISCARD);
+ dump_type_to_string(MARK);
+ return;
+}
+#undef dump_type_to_string
+
/*
* Construct a log-writes mapping:
- * log-writes <dev_path> <log_dev_path>
+ * log-writes <dev_path> <log_dev_path> [<option feature> ...]
+ * option feature can be:
+ * - dump_type=<flags>
+ * flags can be ALL, METADATA, FUA, FLUSH, DISCARD or any of them combined
+ * with '|'.
+ * Default value is ALL.
+ *
+ * This will make log-writes only to record writes with certain type.
+ * E.g dump_type=METADATA|FUA|FLUSH|DISCARD will only record metadata writes
+ * and save log device space.
*/
static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct log_writes_c *lc;
struct dm_arg_set as;
const char *devname, *logdevname;
+ const char *arg_name;
int ret;
as.argc = argc;
@@ -533,8 +618,10 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
init_waitqueue_head(&lc->wait);
atomic_set(&lc->io_blocks, 0);
atomic_set(&lc->pending_blocks, 0);
+ lc->dump_type = (u32)-1;
devname = dm_shift_arg(&as);
+ argc--;
ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev);
if (ret) {
ti->error = "Device lookup failed";
@@ -542,6 +629,7 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
}
logdevname = dm_shift_arg(&as);
+ argc--;
ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table),
&lc->logdev);
if (ret) {
@@ -550,15 +638,35 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad;
}
+ while (argc) {
+ arg_name = dm_shift_arg(&as);
+ argc--;
+
+ if (!arg_name) {
+ ti->error = "Insufficient feature arguments";
+ goto free_all;
+ }
+ /* dump_type= */
+ if (!strncasecmp(arg_name, "dump_type=", strlen("dump_type="))) {
+ ret = parse_dump_types(lc,
+ arg_name + strlen("dump_type="));
+ if (ret < 0) {
+ ti->error = "Bad dump type";
+ goto free_all;
+ }
+ continue;
+ }
+ ti->error = "Unrecognised log-writes feature requested";
+ goto free_all;
+ }
+
lc->sectorsize = bdev_logical_block_size(lc->dev->bdev);
lc->sectorshift = ilog2(lc->sectorsize);
lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
if (IS_ERR(lc->log_kthread)) {
ret = PTR_ERR(lc->log_kthread);
ti->error = "Couldn't alloc kthread";
- dm_put_device(ti, lc->dev);
- dm_put_device(ti, lc->logdev);
- goto bad;
+ goto free_all;
}
/*
@@ -579,6 +687,9 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->private = lc;
return 0;
+free_all:
+ dm_put_device(ti, lc->dev);
+ dm_put_device(ti, lc->logdev);
bad:
kfree(lc);
return ret;
@@ -589,6 +700,8 @@ static int log_mark(struct log_writes_c *lc, char *data)
struct pending_block *block;
size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry);
+ if (!(lc->dump_type & LOG_MARK_FLAG))
+ goto wake_up;
block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
if (!block) {
DMERR("Error allocating pending block");
@@ -607,6 +720,7 @@ static int log_mark(struct log_writes_c *lc, char *data)
spin_lock_irq(&lc->blocks_lock);
list_add_tail(&block->list, &lc->logging_blocks);
spin_unlock_irq(&lc->blocks_lock);
+wake_up:
wake_up_process(lc->log_kthread);
return 0;
}
@@ -643,6 +757,22 @@ static void normal_map_bio(struct dm_target *ti, struct bio *bio)
bio_set_dev(bio, lc->dev->bdev);
}
+static bool need_record(struct log_writes_c *lc, struct bio *bio)
+{
+ if (lc->dump_type == (u32)-1)
+ return true;
+
+ if (lc->dump_type & LOG_METADATA_FLAG && (bio->bi_opf & REQ_META))
+ return true;
+ if (lc->dump_type & LOG_FUA_FLAG && (bio->bi_opf & REQ_FUA))
+ return true;
+ if (lc->dump_type & LOG_FLUSH_FLAG && (bio->bi_opf & REQ_PREFLUSH))
+ return true;
+ if (lc->dump_type & LOG_DISCARD_FLAG && (bio_op(bio) == REQ_PREFLUSH))
+ return true;
+ return false;
+}
+
static int log_writes_map(struct dm_target *ti, struct bio *bio)
{
struct log_writes_c *lc = ti->private;
@@ -673,6 +803,9 @@ static int log_writes_map(struct dm_target *ti, struct bio *bio)
if (!bio_sectors(bio) && !flush_bio)
goto map_bio;
+ /* Check against lc->dump_type */
+ if (!need_record(lc, bio))
+ goto map_bio;
/*
* Discards will have bi_size set but there's no actual data, so just
* allocate the size of the pending block.
@@ -803,6 +936,7 @@ static void log_writes_status(struct dm_target *ti, status_type_t type,
{
unsigned sz = 0;
struct log_writes_c *lc = ti->private;
+ char dump_type_buf[DUMP_TYPES_BUF_SIZE];
switch (type) {
case STATUSTYPE_INFO:
@@ -813,7 +947,9 @@ static void log_writes_status(struct dm_target *ti, status_type_t type,
break;
case STATUSTYPE_TABLE:
- DMEMIT("%s %s", lc->dev->name, lc->logdev->name);
+ status_dump_types(lc, dump_type_buf);
+ DMEMIT("%s %s dump_type=%s", lc->dev->name, lc->logdev->name,
+ dump_type_buf);
break;
}
}
--
2.22.0
--
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