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nilfs2: get rid of sget use for acquiring nilfs object
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This will change the way to obtain nilfs object in nilfs_get_sb()
function.

Previously, a preliminary sget() call was performed, and the nilfs
object was acquired from a super block instance found by the sget()
call.

This patch, instead, instroduces a new dedicated function
find_or_create_nilfs(); as the name implies, the function finds an
existent nilfs object from a global list or creates a new one if no
object is found on the device.

Signed-off-by: Ryusuke Konishi <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Al Viro <[email protected]>
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@konis
konis authored and Al Viro committed Jun 12, 2009
1 parent 81fc20b commit 33c8e57
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Showing 3 changed files with 76 additions and 65 deletions.
80 changes: 19 additions & 61 deletions fs/nilfs2/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1059,13 +1059,6 @@ static int nilfs_set_bdev_super(struct super_block *s, void *data)
}

static int nilfs_test_bdev_super(struct super_block *s, void *data)
{
struct nilfs_super_data *sd = data;

return s->s_bdev == sd->bdev;
}

static int nilfs_test_bdev_super2(struct super_block *s, void *data)
{
struct nilfs_super_data *sd = data;
int ret;
Expand Down Expand Up @@ -1096,8 +1089,8 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
const char *dev_name, void *data, struct vfsmount *mnt)
{
struct nilfs_super_data sd;
struct super_block *s, *s2;
struct the_nilfs *nilfs = NULL;
struct super_block *s;
struct the_nilfs *nilfs;
int err, need_to_close = 1;

sd.bdev = open_bdev_exclusive(dev_name, flags, fs_type);
Expand All @@ -1118,11 +1111,12 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
goto failed;
}

/*
* once the super is inserted into the list by sget, s_umount
* will protect the lockfs code from trying to start a snapshot
* while we are mounting
*/
nilfs = find_or_create_nilfs(sd.bdev);
if (!nilfs) {
err = -ENOMEM;
goto failed;
}

down(&sd.bdev->bd_mount_sem);
if (!sd.cno &&
(err = test_exclusive_mount(fs_type, sd.bdev, flags ^ MS_RDONLY))) {
Expand All @@ -1131,51 +1125,22 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
}

/*
* Phase-1: search any existent instance and get the_nilfs
* Search specified snapshot or R/W mode super_block
*/
s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
if (IS_ERR(s))
goto error_s;

if (!s->s_root) {
err = -ENOMEM;
nilfs = alloc_nilfs(sd.bdev);
if (!nilfs)
goto cancel_new;
} else {
struct nilfs_sb_info *sbi = NILFS_SB(s);
if (!sd.cno)
/* trying to get the latest checkpoint. */
sd.cno = nilfs_last_cno(nilfs);

/*
* s_umount protects super_block from unmount process;
* It covers pointers of nilfs_sb_info and the_nilfs.
*/
nilfs = sbi->s_nilfs;
get_nilfs(nilfs);
up_write(&s->s_umount);

/*
* Phase-2: search specified snapshot or R/W mode super_block
*/
if (!sd.cno)
/* trying to get the latest checkpoint. */
sd.cno = nilfs_last_cno(nilfs);

s2 = sget(fs_type, nilfs_test_bdev_super2,
nilfs_set_bdev_super, &sd);
deactivate_super(s);
/*
* Although deactivate_super() invokes close_bdev_exclusive() at
* kill_block_super(). Here, s is an existent mount; we need
* one more close_bdev_exclusive() call.
*/
s = s2;
if (IS_ERR(s))
goto error_s;
s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
if (IS_ERR(s)) {
err = PTR_ERR(s);
goto failed_unlock;
}

if (!s->s_root) {
char b[BDEVNAME_SIZE];

/* New superblock instance created */
s->s_flags = flags;
strlcpy(s->s_id, bdevname(sd.bdev, b), sizeof(s->s_id));
sb_set_blocksize(s, block_size(sd.bdev));
Expand All @@ -1195,15 +1160,9 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
simple_set_mnt(mnt, s);
return 0;

error_s:
up(&sd.bdev->bd_mount_sem);
if (nilfs)
put_nilfs(nilfs);
close_bdev_exclusive(sd.bdev, flags);
return PTR_ERR(s);

failed_unlock:
up(&sd.bdev->bd_mount_sem);
put_nilfs(nilfs);
failed:
close_bdev_exclusive(sd.bdev, flags);

Expand All @@ -1212,8 +1171,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
cancel_new:
/* Abandoning the newly allocated superblock */
up(&sd.bdev->bd_mount_sem);
if (nilfs)
put_nilfs(nilfs);
put_nilfs(nilfs);
up_write(&s->s_umount);
deactivate_super(s);
/*
Expand Down
57 changes: 54 additions & 3 deletions fs/nilfs2/the_nilfs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,10 @@
#include "seglist.h"
#include "segbuf.h"


static LIST_HEAD(nilfs_objects);
static DEFINE_SPINLOCK(nilfs_lock);

void nilfs_set_last_segment(struct the_nilfs *nilfs,
sector_t start_blocknr, u64 seq, __u64 cno)
{
Expand All @@ -55,7 +59,7 @@ void nilfs_set_last_segment(struct the_nilfs *nilfs,
* Return Value: On success, pointer to the_nilfs is returned.
* On error, NULL is returned.
*/
struct the_nilfs *alloc_nilfs(struct block_device *bdev)
static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
{
struct the_nilfs *nilfs;

Expand All @@ -69,6 +73,7 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
atomic_set(&nilfs->ns_ndirtyblks, 0);
init_rwsem(&nilfs->ns_sem);
mutex_init(&nilfs->ns_writer_mutex);
INIT_LIST_HEAD(&nilfs->ns_list);
INIT_LIST_HEAD(&nilfs->ns_supers);
spin_lock_init(&nilfs->ns_last_segment_lock);
nilfs->ns_gc_inodes_h = NULL;
Expand All @@ -77,6 +82,45 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
return nilfs;
}

/**
* find_or_create_nilfs - find or create nilfs object
* @bdev: block device to which the_nilfs is related
*
* find_nilfs() looks up an existent nilfs object created on the
* device and gets the reference count of the object. If no nilfs object
* is found on the device, a new nilfs object is allocated.
*
* Return Value: On success, pointer to the nilfs object is returned.
* On error, NULL is returned.
*/
struct the_nilfs *find_or_create_nilfs(struct block_device *bdev)
{
struct the_nilfs *nilfs, *new = NULL;

retry:
spin_lock(&nilfs_lock);
list_for_each_entry(nilfs, &nilfs_objects, ns_list) {
if (nilfs->ns_bdev == bdev) {
get_nilfs(nilfs);
spin_unlock(&nilfs_lock);
if (new)
put_nilfs(new);
return nilfs; /* existing object */
}
}
if (new) {
list_add_tail(&new->ns_list, &nilfs_objects);
spin_unlock(&nilfs_lock);
return new; /* new object */
}
spin_unlock(&nilfs_lock);

new = alloc_nilfs(bdev);
if (new)
goto retry;
return NULL; /* insufficient memory */
}

/**
* put_nilfs - release a reference to the_nilfs
* @nilfs: the_nilfs structure to be released
Expand All @@ -86,13 +130,20 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
*/
void put_nilfs(struct the_nilfs *nilfs)
{
if (!atomic_dec_and_test(&nilfs->ns_count))
spin_lock(&nilfs_lock);
if (!atomic_dec_and_test(&nilfs->ns_count)) {
spin_unlock(&nilfs_lock);
return;
}
list_del_init(&nilfs->ns_list);
spin_unlock(&nilfs_lock);

/*
* Increment of ns_count never occur below because the caller
* Increment of ns_count never occurs below because the caller
* of get_nilfs() holds at least one reference to the_nilfs.
* Thus its exclusion control is not required here.
*/

might_sleep();
if (nilfs_loaded(nilfs)) {
nilfs_mdt_clear(nilfs->ns_sufile);
Expand Down
4 changes: 3 additions & 1 deletion fs/nilfs2/the_nilfs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ enum {
* struct the_nilfs - struct to supervise multiple nilfs mount points
* @ns_flags: flags
* @ns_count: reference count
* @ns_list: list head for nilfs_list
* @ns_bdev: block device
* @ns_bdi: backing dev info
* @ns_writer: back pointer to writable nilfs_sb_info
Expand Down Expand Up @@ -88,6 +89,7 @@ enum {
struct the_nilfs {
unsigned long ns_flags;
atomic_t ns_count;
struct list_head ns_list;

struct block_device *ns_bdev;
struct backing_dev_info *ns_bdi;
Expand Down Expand Up @@ -191,7 +193,7 @@ THE_NILFS_FNS(DISCONTINUED, discontinued)
#define NILFS_ALTSB_FREQ 60 /* spare superblock */

void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
struct the_nilfs *alloc_nilfs(struct block_device *);
struct the_nilfs *find_or_create_nilfs(struct block_device *);
void put_nilfs(struct the_nilfs *);
int init_nilfs(struct the_nilfs *, struct nilfs_sb_info *, char *);
int load_nilfs(struct the_nilfs *, struct nilfs_sb_info *);
Expand Down

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