vm.block_dump is nasty in that it dumps IO traces directly to printk.
It isn't scalable and can easily lead to looping behavior - IO
generating kernel message which in turn genreates log IO, ad
infinitum.
Now that proper tracepoints are in place, vm.block_dump isn't
necessary. Generate a warning if used so that it can be removed down
the road.
Cc: Added contact info as suggested by Jan.
Signed-off-by: Tejun Heo <t...@kernel.org>
Cc: Jan Kara <j...@suse.cz>
---
include/linux/writeback.h | 3 +++
kernel/sysctl.c | 2 +-
mm/page-writeback.c | 15 +++++++++++++++
patches/series | 1 +
4 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index b82a83a..678ee6d 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -143,6 +143,9 @@ extern int dirty_ratio_handler(struct ctl_table *table, int
write,
extern int dirty_bytes_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
+extern int block_dump_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos);
struct ctl_table;
int dirty_writeback_centisecs_handler(struct ctl_table *, int,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c88878d..9e7f7b5 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1288,7 +1288,7 @@ static struct ctl_table vm_table[] = {
.data = &block_dump,
.maxlen = sizeof(block_dump),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = block_dump_handler,
.extra1 = &zero,
},
{
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 6f42712..605632d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -390,6 +390,21 @@ int dirty_bytes_handler(struct ctl_table *table, int write,
return ret;
}
+int block_dump_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ static bool warned = false;
+ int ret;
+
+ ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ if (!warned && block_dump) {
+ pr_warning("sysctl: vm.block_dump is scheduled for removal. Use
tracepoints instead.\n");
+ pr_warning("sysctl: Please contact Jens Axboe <ax...@kernel.dk>
if you require this.\n");
+ warned = true;
+ }
+ return ret;
+}
+
static unsigned long wp_next_time(unsigned long cur_time)
{
cur_time += VM_COMPLETIONS_PERIOD_LEN;
diff --git a/patches/series b/patches/series
index 9fb9bfe..b2582cb 100644
--- a/patches/series
+++ b/patches/series
@@ -18,3 +18,4 @@ kill-pool-gcwq
remove-gcwq
rename-nr_running
cleanup-leftovers
+dbg
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