I've been carrying a patch in the unstable portion of the patch series
for a while now to debug problems with delayed allocation. This
allows us to observe the state of which inodes have inodes subject for
delayed allocation, and how many data/metadata blocks have been
reserved.
I've finally cleaned it up enough that it's something where I wouldn't
feel terrible dropping it into the mainline kernel. (It's still a
little gross, but it's not truly horrifying any more.)
What do people think? Is this something that's worth having in the
kernel sources? Or shall I continue carrying it as an out-of-tree
debugging patch?
(Note: we can use similar technique to gain visibility into the status
the extent status LRU list.)
- Ted
>From f6417debc1c96a9dfa6b9f19da14eff35bf0f504 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@xxxxxxx>
Date: Thu, 20 Jun 2013 12:35:39 -0400
Subject: [PATCH] ext4: add delalloc debugging
This adds a file in /proc/fs/ext4/<dev> which when opened for reading,
will trigger debugging code that dumps a lot of information about
inodes subject to delayed allocation to the console.
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
---
fs/ext4/super.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 77 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 85b3dd6..ecb8256 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1832,6 +1832,74 @@ static const struct file_operations ext4_seq_options_fops = {
.release = single_release,
};
+#ifdef CONFIG_EXT4_DEBUG
+static void print_inode_delalloc_info(struct inode *inode)
+{
+ if (!EXT4_I(inode)->i_reserved_data_blocks ||
+ !EXT4_I(inode)->i_reserved_meta_blocks)
+ return;
+
+ printk(KERN_DEBUG "ino %lu: %u %u\n", inode->i_ino,
+ EXT4_I(inode)->i_reserved_data_blocks,
+ EXT4_I(inode)->i_reserved_meta_blocks);
+}
+
+static int debug_delalloc_show(struct seq_file *seq, void *offset)
+{
+ return 0;
+}
+
+static int options_delalloc_debug_open_fs(struct inode *proc_inode,
+ struct file *file)
+{
+ struct super_block *sb = PDE_DATA(proc_inode);
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct inode *inode;
+ extern spinlock_t inode_sb_list_lock;
+
+ printk(KERN_DEBUG "EXT4-fs debug delalloc of %s\n", sb->s_id);
+ printk(KERN_DEBUG "EXT4-fs: dirty clusters %lld free clusters %lld\n",
+ percpu_counter_sum(&sbi->s_dirtyclusters_counter),
+ percpu_counter_sum(&sbi->s_freeclusters_counter));
+
+#ifndef MODULE
+ spin_lock(&inode_sb_list_lock);
+ if (!list_empty(&sb->s_bdi->wb.b_dirty)) {
+ printk(KERN_DEBUG "s_bdi->wb.b_dirty list:\n");
+ list_for_each_entry(inode, &sb->s_bdi->wb.b_dirty,
+ i_wb_list) {
+ print_inode_delalloc_info(inode);
+ }
+ }
+ if (!list_empty(&sb->s_bdi->wb.b_io)) {
+ printk(KERN_DEBUG "s_bdi->wb.b_io list:\n");
+ list_for_each_entry(inode, &sb->s_bdi->wb.b_io,
+ i_wb_list) {
+ print_inode_delalloc_info(inode);
+ }
+ }
+ if (!list_empty(&sb->s_bdi->wb.b_more_io)) {
+ printk(KERN_DEBUG "s_bdi->wb.b_more_io list:\n");
+ list_for_each_entry(inode, &sb->s_bdi->wb.b_more_io,
+ i_wb_list) {
+ print_inode_delalloc_info(inode);
+ }
+ }
+ spin_unlock(&inode_sb_list_lock);
+ printk(KERN_DEBUG "ext4 debug delalloc done\n");
+#endif
+ return single_open(file, debug_delalloc_show, sb);
+}
+
+static const struct file_operations ext4_seq_delalloc_debug_fops = {
+ .owner = THIS_MODULE,
+ .open = options_delalloc_debug_open_fs,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+#endif
+
static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
int read_only)
{
@@ -3764,9 +3832,14 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
if (ext4_proc_root)
sbi->s_proc = proc_mkdir(sb->s_id, ext4_proc_root);
- if (sbi->s_proc)
+ if (sbi->s_proc) {
proc_create_data("options", S_IRUGO, sbi->s_proc,
&ext4_seq_options_fops, sb);
+#ifdef CONFIG_EXT4_DEBUG
+ proc_create_data("delalloc_debug", S_IRUSR, sbi->s_proc,
+ &ext4_seq_delalloc_debug_fops, sb);
+#endif
+ }
bgl_lock_init(sbi->s_blockgroup_lock);
@@ -4149,6 +4222,9 @@ failed_mount:
crypto_free_shash(sbi->s_chksum_driver);
if (sbi->s_proc) {
remove_proc_entry("options", sbi->s_proc);
+#ifdef CONFIG_EXT4_DEBUG
+ remove_proc_entry("delalloc_debug", sbi->s_proc);
+#endif
remove_proc_entry(sb->s_id, ext4_proc_root);
}
#ifdef CONFIG_QUOTA
--
1.7.12.rc0.22.gcdd159b
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