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linux/fs/efs/super.c
Nick Piggin fa0d7e3de6 fs: icache RCU free inodes 
RCU free the struct inode. This will allow:

- Subsequent store-free path walking patch. The inode must be consulted for
  permissions when walking, so an RCU inode reference is a must.
- sb_inode_list_lock to be moved inside i_lock because sb list walkers who want
  to take i_lock no longer need to take sb_inode_list_lock to walk the list in
  the first place. This will simplify and optimize locking.
- Could remove some nested trylock loops in dcache code
- Could potentially simplify things a bit in VM land. Do not need to take the
  page lock to follow page->mapping.

The downsides of this is the performance cost of using RCU. In a simple
creat/unlink microbenchmark, performance drops by about 10% due to inability to
reuse cache-hot slab objects. As iterations increase and RCU freeing starts
kicking over, this increases to about 20%.

In cases where inode lifetimes are longer (ie. many inodes may be allocated
during the average life span of a single inode), a lot of this cache reuse is
not applicable, so the regression caused by this patch is smaller.

The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU,
however this adds some complexity to list walking and store-free path walking,
so I prefer to implement this at a later date, if it is shown to be a win in
real situations. I haven't found a regression in any non-micro benchmark so I
doubt it will be a problem.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:26 +11:00

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/*
* super.c
*
* Copyright (c) 1999 Al Smith
*
* Portions derived from work (c) 1995,1996 Christian Vogelgsang.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/exportfs.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>
#include "efs.h"
#include <linux/efs_vh.h>
#include <linux/efs_fs_sb.h>
static int efs_statfs(struct dentry *dentry, struct kstatfs *buf);
static int efs_fill_super(struct super_block *s, void *d, int silent);
static struct dentry *efs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, efs_fill_super);
}
static struct file_system_type efs_fs_type = {
.owner = THIS_MODULE,
.name = "efs",
.mount = efs_mount,
.kill_sb = kill_block_super,
.fs_flags = FS_REQUIRES_DEV,
};
static struct pt_types sgi_pt_types[] = {
{0x00, "SGI vh"},
{0x01, "SGI trkrepl"},
{0x02, "SGI secrepl"},
{0x03, "SGI raw"},
{0x04, "SGI bsd"},
{SGI_SYSV, "SGI sysv"},
{0x06, "SGI vol"},
{SGI_EFS, "SGI efs"},
{0x08, "SGI lv"},
{0x09, "SGI rlv"},
{0x0A, "SGI xfs"},
{0x0B, "SGI xfslog"},
{0x0C, "SGI xlv"},
{0x82, "Linux swap"},
{0x83, "Linux native"},
{0, NULL}
};
static struct kmem_cache * efs_inode_cachep;
static struct inode *efs_alloc_inode(struct super_block *sb)
{
struct efs_inode_info *ei;
ei = (struct efs_inode_info *)kmem_cache_alloc(efs_inode_cachep, GFP_KERNEL);
if (!ei)
return NULL;
return &ei->vfs_inode;
}
static void efs_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
INIT_LIST_HEAD(&inode->i_dentry);
kmem_cache_free(efs_inode_cachep, INODE_INFO(inode));
}
static void efs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, efs_i_callback);
}
static void init_once(void *foo)
{
struct efs_inode_info *ei = (struct efs_inode_info *) foo;
inode_init_once(&ei->vfs_inode);
}
static int init_inodecache(void)
{
efs_inode_cachep = kmem_cache_create("efs_inode_cache",
sizeof(struct efs_inode_info),
0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
init_once);
if (efs_inode_cachep == NULL)
return -ENOMEM;
return 0;
}
static void destroy_inodecache(void)
{
kmem_cache_destroy(efs_inode_cachep);
}
static void efs_put_super(struct super_block *s)
{
kfree(s->s_fs_info);
s->s_fs_info = NULL;
}
static int efs_remount(struct super_block *sb, int *flags, char *data)
{
*flags |= MS_RDONLY;
return 0;
}
static const struct super_operations efs_superblock_operations = {
.alloc_inode = efs_alloc_inode,
.destroy_inode = efs_destroy_inode,
.put_super = efs_put_super,
.statfs = efs_statfs,
.remount_fs = efs_remount,
};
static const struct export_operations efs_export_ops = {
.fh_to_dentry = efs_fh_to_dentry,
.fh_to_parent = efs_fh_to_parent,
.get_parent = efs_get_parent,
};
static int __init init_efs_fs(void) {
int err;
printk("EFS: "EFS_VERSION" - http://aeschi.ch.eu.org/efs/\n");
err = init_inodecache();
if (err)
goto out1;
err = register_filesystem(&efs_fs_type);
if (err)
goto out;
return 0;
out:
destroy_inodecache();
out1:
return err;
}
static void __exit exit_efs_fs(void) {
unregister_filesystem(&efs_fs_type);
destroy_inodecache();
}
module_init(init_efs_fs)
module_exit(exit_efs_fs)
static efs_block_t efs_validate_vh(struct volume_header *vh) {
int i;
__be32 cs, *ui;
int csum;
efs_block_t sblock = 0; /* shuts up gcc */
struct pt_types *pt_entry;
int pt_type, slice = -1;
if (be32_to_cpu(vh->vh_magic) != VHMAGIC) {
/*
* assume that we're dealing with a partition and allow
* read_super() to try and detect a valid superblock
* on the next block.
*/
return 0;
}
ui = ((__be32 *) (vh + 1)) - 1;
for(csum = 0; ui >= ((__be32 *) vh);) {
cs = *ui--;
csum += be32_to_cpu(cs);
}
if (csum) {
printk(KERN_INFO "EFS: SGI disklabel: checksum bad, label corrupted\n");
return 0;
}
#ifdef DEBUG
printk(KERN_DEBUG "EFS: bf: \"%16s\"\n", vh->vh_bootfile);
for(i = 0; i < NVDIR; i++) {
int j;
char name[VDNAMESIZE+1];
for(j = 0; j < VDNAMESIZE; j++) {
name[j] = vh->vh_vd[i].vd_name[j];
}
name[j] = (char) 0;
if (name[0]) {
printk(KERN_DEBUG "EFS: vh: %8s block: 0x%08x size: 0x%08x\n",
name,
(int) be32_to_cpu(vh->vh_vd[i].vd_lbn),
(int) be32_to_cpu(vh->vh_vd[i].vd_nbytes));
}
}
#endif
for(i = 0; i < NPARTAB; i++) {
pt_type = (int) be32_to_cpu(vh->vh_pt[i].pt_type);
for(pt_entry = sgi_pt_types; pt_entry->pt_name; pt_entry++) {
if (pt_type == pt_entry->pt_type) break;
}
#ifdef DEBUG
if (be32_to_cpu(vh->vh_pt[i].pt_nblks)) {
printk(KERN_DEBUG "EFS: pt %2d: start: %08d size: %08d type: 0x%02x (%s)\n",
i,
(int) be32_to_cpu(vh->vh_pt[i].pt_firstlbn),
(int) be32_to_cpu(vh->vh_pt[i].pt_nblks),
pt_type,
(pt_entry->pt_name) ? pt_entry->pt_name : "unknown");
}
#endif
if (IS_EFS(pt_type)) {
sblock = be32_to_cpu(vh->vh_pt[i].pt_firstlbn);
slice = i;
}
}
if (slice == -1) {
printk(KERN_NOTICE "EFS: partition table contained no EFS partitions\n");
#ifdef DEBUG
} else {
printk(KERN_INFO "EFS: using slice %d (type %s, offset 0x%x)\n",
slice,
(pt_entry->pt_name) ? pt_entry->pt_name : "unknown",
sblock);
#endif
}
return sblock;
}
static int efs_validate_super(struct efs_sb_info *sb, struct efs_super *super) {
if (!IS_EFS_MAGIC(be32_to_cpu(super->fs_magic)))
return -1;
sb->fs_magic = be32_to_cpu(super->fs_magic);
sb->total_blocks = be32_to_cpu(super->fs_size);
sb->first_block = be32_to_cpu(super->fs_firstcg);
sb->group_size = be32_to_cpu(super->fs_cgfsize);
sb->data_free = be32_to_cpu(super->fs_tfree);
sb->inode_free = be32_to_cpu(super->fs_tinode);
sb->inode_blocks = be16_to_cpu(super->fs_cgisize);
sb->total_groups = be16_to_cpu(super->fs_ncg);
return 0;
}
static int efs_fill_super(struct super_block *s, void *d, int silent)
{
struct efs_sb_info *sb;
struct buffer_head *bh;
struct inode *root;
int ret = -EINVAL;
sb = kzalloc(sizeof(struct efs_sb_info), GFP_KERNEL);
if (!sb)
return -ENOMEM;
s->s_fs_info = sb;
s->s_magic = EFS_SUPER_MAGIC;
if (!sb_set_blocksize(s, EFS_BLOCKSIZE)) {
printk(KERN_ERR "EFS: device does not support %d byte blocks\n",
EFS_BLOCKSIZE);
goto out_no_fs_ul;
}
/* read the vh (volume header) block */
bh = sb_bread(s, 0);
if (!bh) {
printk(KERN_ERR "EFS: cannot read volume header\n");
goto out_no_fs_ul;
}
/*
* if this returns zero then we didn't find any partition table.
* this isn't (yet) an error - just assume for the moment that
* the device is valid and go on to search for a superblock.
*/
sb->fs_start = efs_validate_vh((struct volume_header *) bh->b_data);
brelse(bh);
if (sb->fs_start == -1) {
goto out_no_fs_ul;
}
bh = sb_bread(s, sb->fs_start + EFS_SUPER);
if (!bh) {
printk(KERN_ERR "EFS: cannot read superblock\n");
goto out_no_fs_ul;
}
if (efs_validate_super(sb, (struct efs_super *) bh->b_data)) {
#ifdef DEBUG
printk(KERN_WARNING "EFS: invalid superblock at block %u\n", sb->fs_start + EFS_SUPER);
#endif
brelse(bh);
goto out_no_fs_ul;
}
brelse(bh);
if (!(s->s_flags & MS_RDONLY)) {
#ifdef DEBUG
printk(KERN_INFO "EFS: forcing read-only mode\n");
#endif
s->s_flags |= MS_RDONLY;
}
s->s_op = &efs_superblock_operations;
s->s_export_op = &efs_export_ops;
root = efs_iget(s, EFS_ROOTINODE);
if (IS_ERR(root)) {
printk(KERN_ERR "EFS: get root inode failed\n");
ret = PTR_ERR(root);
goto out_no_fs;
}
s->s_root = d_alloc_root(root);
if (!(s->s_root)) {
printk(KERN_ERR "EFS: get root dentry failed\n");
iput(root);
ret = -ENOMEM;
goto out_no_fs;
}
return 0;
out_no_fs_ul:
out_no_fs:
s->s_fs_info = NULL;
kfree(sb);
return ret;
}
static int efs_statfs(struct dentry *dentry, struct kstatfs *buf) {
struct super_block *sb = dentry->d_sb;
struct efs_sb_info *sbi = SUPER_INFO(sb);
u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
buf->f_type = EFS_SUPER_MAGIC; /* efs magic number */
buf->f_bsize = EFS_BLOCKSIZE; /* blocksize */
buf->f_blocks = sbi->total_groups * /* total data blocks */
(sbi->group_size - sbi->inode_blocks);
buf->f_bfree = sbi->data_free; /* free data blocks */
buf->f_bavail = sbi->data_free; /* free blocks for non-root */
buf->f_files = sbi->total_groups * /* total inodes */
sbi->inode_blocks *
(EFS_BLOCKSIZE / sizeof(struct efs_dinode));
buf->f_ffree = sbi->inode_free; /* free inodes */
buf->f_fsid.val[0] = (u32)id;
buf->f_fsid.val[1] = (u32)(id >> 32);
buf->f_namelen = EFS_MAXNAMELEN; /* max filename length */
return 0;
}
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