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Date: Thu, 21 May 2009 16:01:03 -0400
From: Theodore Ts'o <tytso@....edu>
To: linux-kernel@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org, Theodore Ts'o <tytso@....edu>
Subject: [PATCH 5/5] Dump the inode structure (for debugging purposes only)
This is not intended for merging; but it's useful for determining how
much varous fields in the struct inode space, and whether there is any
padding leading to waste, especially on a 64-bit platforms.
For example:
Begin dump of struct inode (size 1144)
i_hash : 0 16 0
i_list : 16 16 0
i_sb_list : 32 16 0
i_dentry : 48 16 0
i_ino : 64 8 0
i_count : 72 4 0
i_nlink : 76 4 0
i_uid : 80 4 0
i_gid : 84 4 0
i_rdev : 88 4 0
i_version : 96 8 4
i_size : 104 8 0
i_atime : 112 16 0
i_mtime : 128 16 0
i_ctime : 144 16 0
i_blocks : 160 8 0
i_blkbits : 168 4 0
i_bytes : 172 2 0
i_mode : 174 2 0
i_lock : 176 64 0
i_mutex : 240 152 0
i_alloc_sem: 392 128 0
i_op : 520 8 0
i_fop : 528 8 0
i_sb : 536 8 0
i_flock : 544 8 0
i_mapping : 552 8 0
i_data : 560 328 0
i_dquot : 888 16 0
i_devices : 904 16 0
i_pipe : 920 8 0
i_bdev : 920 8 -8
i_cdev : 920 8 -8
i_generation: 928 4 0
i_dnotify_mask: 932 4 0
i_dnotify : 936 8 0
inotify_watches: 944 16 0
inotify_mutex: 960 152 0
dirtied_when: 1112 8 0
i_state : 1120 2 0
i_flags : 1122 2 0
i_writecount: 1124 4 0
i_security: 1128 8 0
i_private : 1136 8 0
This shows us that i_data, an struct address_space data structure,
takes 328 bytes; i_mutex takes 152 bytes, the i_alloc_sem rw_semaphore
takes 128 bytes, and the i_lock spinlock takes 64 bytes. A lot of
this space is due to varous LOCKDEP and spinlock debugging options.
(With all debugging turned off, the inode structure shrinks from 1144
bytes to 560 bytes, with i_data being 144 bytes, i_mutex being 32
bytes, i_alloc_sem being 24 bytes, and i_lock taking 4 bytes.)
---
fs/Makefile | 1 +
fs/inode-struct-dumper.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 88 insertions(+), 0 deletions(-)
create mode 100644 fs/inode-struct-dumper.c
diff --git a/fs/Makefile b/fs/Makefile
index af6d047..196f3f5 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_EVENTFD) += eventfd.o
obj-$(CONFIG_AIO) += aio.o
obj-$(CONFIG_FILE_LOCKING) += locks.o
obj-$(CONFIG_COMPAT) += compat.o compat_ioctl.o
+obj-y += inode-struct-dumper.o
nfsd-$(CONFIG_NFSD) := nfsctl.o
obj-y += $(nfsd-y) $(nfsd-m)
diff --git a/fs/inode-struct-dumper.c b/fs/inode-struct-dumper.c
new file mode 100644
index 0000000..c85d792
--- /dev/null
+++ b/fs/inode-struct-dumper.c
@@ -0,0 +1,87 @@
+/*
+ * inode struct dumper --- dump out the inode structure
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/stddef.h>
+
+#define ELEMENT(xx) { \
+ offset=offsetof(struct inode, xx); \
+ size=sizeof(p->xx); \
+ printk(KERN_NOTICE "%-10s: %d %d %d\n", #xx, \
+ offset, size, offset-(last_offset+last_size)); \
+ last_offset=offset; \
+ last_size = size; \
+ }
+
+static int __init dumper_init(void)
+{
+ struct inode *p;
+ int offset, size, last_offset=0, last_size=0;
+
+ printk(KERN_NOTICE "Begin dump of struct inode (size %lu)\n",
+ sizeof(struct inode));
+ ELEMENT(i_hash);
+ ELEMENT(i_list);
+ ELEMENT(i_sb_list);
+ ELEMENT(i_dentry);
+ ELEMENT(i_ino);
+ ELEMENT(i_count);
+ ELEMENT(i_nlink);
+ ELEMENT(i_uid);
+ ELEMENT(i_gid);
+ ELEMENT(i_rdev);
+ ELEMENT(i_version);
+ ELEMENT(i_size);
+#ifdef __NEED_I_SIZE_ORDERED
+ ELEMENT(i_size_seqcount);
+#endif
+ ELEMENT(i_atime);
+ ELEMENT(i_mtime);
+ ELEMENT(i_ctime);
+ ELEMENT(i_blocks);
+ ELEMENT(i_blkbits);
+ ELEMENT(i_bytes);
+ ELEMENT(i_mode);
+ ELEMENT(i_lock);
+ ELEMENT(i_mutex);
+ ELEMENT(i_alloc_sem);
+ ELEMENT(i_op);
+ ELEMENT(i_fop);
+ ELEMENT(i_sb);
+ ELEMENT(i_flock);
+ ELEMENT(i_mapping);
+ ELEMENT(i_data);
+#ifdef CONFIG_QUOTA
+ ELEMENT(i_dquot);
+#endif
+ ELEMENT(i_devices);
+ ELEMENT(i_pipe);
+ ELEMENT(i_bdev);
+ ELEMENT(i_cdev);
+ ELEMENT(i_generation);
+#ifdef CONFIG_DNOTIFY
+ ELEMENT(i_dnotify_mask);
+ ELEMENT(i_dnotify);
+#endif
+#ifdef CONFIG_INOTIFY
+ ELEMENT(inotify_watches);
+ ELEMENT(inotify_mutex);
+#endif
+ ELEMENT(dirtied_when);
+ ELEMENT(i_state);
+ ELEMENT(i_flags);
+ ELEMENT(i_writecount);
+#ifdef CONFIG_SECURITY
+ ELEMENT(i_security);
+#endif
+ ELEMENT(i_private);
+ return 0;
+}
+
+module_init(dumper_init);
+
--
1.6.3.1.1.g75fc.dirty
--
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