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List: linux-nilfs
Subject: [PATCH 10/23] nilfs2: do not allocate multiple super block instances for a device
From: Ryusuke Konishi <konishi.ryusuke () lab ! ntt ! co ! jp>
Date: 2010-09-13 15:37:11
Message-ID: 1284392244-27100-11-git-send-email-konishi.ryusuke () lab ! ntt ! co ! jp
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This stops allocating multiple super block instances for a device.
All snapshots and a current mode mount (i.e. latest tree) will be
controlled with nilfs_root objects that are kept within an sb
instance.
nilfs_get_sb() is rewritten so that it always has a root object for
the latest tree and snapshots make additional root objects.
The root dentry of the latest tree is binded to sb->s_root even if it
isn't attached on a directory. Root dentries of snapshots or the
latest tree are binded to mnt->mnt_root on which they are mounted.
With this patch, nilfs_find_sbinfo() function, nilfs->ns_supers list,
and nilfs->ns_current back pointer, are deleted. In addition,
init_nilfs() and load_nilfs() are simplified since they will be called
once for a device, not repeatedly called for mount points.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
---
fs/nilfs2/sb.h | 5 -
fs/nilfs2/super.c | 216 +++++++++++++++++++++++--------------------------
fs/nilfs2/the_nilfs.c | 89 +--------------------
fs/nilfs2/the_nilfs.h | 16 ----
4 files changed, 101 insertions(+), 225 deletions(-)
diff --git a/fs/nilfs2/sb.h b/fs/nilfs2/sb.h
index 3cc3675..35a0715 100644
--- a/fs/nilfs2/sb.h
+++ b/fs/nilfs2/sb.h
@@ -42,9 +42,6 @@ struct nilfs_sc_info;
* NILFS super-block data in memory
*/
struct nilfs_sb_info {
- /* Snapshot status */
- __u64 s_snapshot_cno; /* Checkpoint number */
-
/* Mount options */
unsigned long s_mount_opt;
uid_t s_resuid;
@@ -57,8 +54,6 @@ struct nilfs_sb_info {
/* Fundamental members */
struct super_block *s_super; /* reverse pointer to super_block */
struct the_nilfs *s_nilfs;
- struct list_head s_list; /* list head for nilfs->ns_supers */
- atomic_t s_count; /* reference count */
/* Segment constructor */
struct list_head s_dirty_files; /* dirty files list */
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 0ebe4c6..bd2eb42 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -358,16 +358,11 @@ static void nilfs_put_super(struct super_block *sb)
nilfs_cleanup_super(sbi);
up_write(&nilfs->ns_sem);
}
- down_write(&nilfs->ns_super_sem);
- if (nilfs->ns_current == sbi)
- nilfs->ns_current = NULL;
- list_del_init(&sbi->s_list);
- up_write(&nilfs->ns_super_sem);
put_nilfs(sbi->s_nilfs);
sbi->s_super = NULL;
sb->s_fs_info = NULL;
- nilfs_put_sbinfo(sbi);
+ kfree(sbi);
unlock_kernel();
}
@@ -505,12 +500,12 @@ static int nilfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
struct super_block *sb = vfs->mnt_sb;
struct nilfs_sb_info *sbi = NILFS_SB(sb);
+ struct nilfs_root *root = NILFS_I(vfs->mnt_root->d_inode)->i_root;
if (!nilfs_test_opt(sbi, BARRIER))
seq_puts(seq, ",nobarrier");
- if (nilfs_test_opt(sbi, SNAPSHOT))
- seq_printf(seq, ",cp=%llu",
- (unsigned long long int)sbi->s_snapshot_cno);
+ if (root->cno != NILFS_CPTREE_CURRENT_CNO)
+ seq_printf(seq, ",cp=%llu", (unsigned long long)root->cno);
if (nilfs_test_opt(sbi, ERRORS_PANIC))
seq_puts(seq, ",errors=panic");
if (nilfs_test_opt(sbi, ERRORS_CONT))
@@ -610,27 +605,11 @@ static int parse_options(char *options, struct super_block *sb, int is_remount)
if (match_int(&args[0], &option) || option <= 0)
return 0;
if (is_remount) {
- if (!nilfs_test_opt(sbi, SNAPSHOT)) {
- printk(KERN_ERR
- "NILFS: cannot change regular "
- "mount to snapshot.\n");
- return 0;
- } else if (option != sbi->s_snapshot_cno) {
- printk(KERN_ERR
- "NILFS: cannot remount to a "
- "different snapshot.\n");
- return 0;
- }
- break;
- }
- if (!(sb->s_flags & MS_RDONLY)) {
- printk(KERN_ERR "NILFS: cannot mount snapshot "
- "read/write. A read-only option is "
- "required.\n");
+ printk(KERN_ERR
+ "NILFS: \"%s\" option is invalid "
+ "for remount.\n", p);
return 0;
}
- sbi->s_snapshot_cno = option;
- nilfs_set_opt(sbi, SNAPSHOT);
break;
case Opt_norecovery:
nilfs_set_opt(sbi, NORECOVERY);
@@ -776,16 +755,32 @@ static int nilfs_get_root_dentry(struct super_block *sb,
goto out;
}
- dentry = d_alloc_root(inode);
- if (!dentry) {
- iput(inode);
- printk(KERN_ERR "NILFS: get root dentry failed\n");
- ret = -ENOMEM;
- goto out;
+ if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
+ dentry = d_find_alias(inode);
+ if (!dentry) {
+ dentry = d_alloc_root(inode);
+ if (!dentry) {
+ iput(inode);
+ ret = -ENOMEM;
+ goto failed_dentry;
+ }
+ } else {
+ iput(inode);
+ }
+ } else {
+ dentry = d_obtain_alias(inode);
+ if (IS_ERR(dentry)) {
+ ret = PTR_ERR(dentry);
+ goto failed_dentry;
+ }
}
*root_dentry = dentry;
out:
return ret;
+
+ failed_dentry:
+ printk(KERN_ERR "NILFS: get root dentry failed\n");
+ goto out;
}
static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
@@ -822,6 +817,25 @@ static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
return ret;
}
+static int nilfs_tree_was_touched(struct dentry *root_dentry)
+{
+ return atomic_read(&root_dentry->d_count) > 1;
+}
+
+/**
+ * nilfs_try_to_shrink_tree() - try to shrink dentries of a checkpoint
+ * @root_dentry: root dentry of the tree to be shrunk
+ *
+ * This function returns true if the tree was in-use.
+ */
+static int nilfs_try_to_shrink_tree(struct dentry *root_dentry)
+{
+ if (have_submounts(root_dentry))
+ return true;
+ shrink_dcache_parent(root_dentry);
+ return nilfs_tree_was_touched(root_dentry);
+}
+
/**
* nilfs_fill_super() - initialize a super block instance
* @sb: super_block
@@ -850,7 +864,6 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
get_nilfs(nilfs);
sbi->s_nilfs = nilfs;
sbi->s_super = sb;
- atomic_set(&sbi->s_count, 1);
err = init_nilfs(nilfs, sbi, (char *)data);
if (err)
@@ -858,7 +871,6 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
spin_lock_init(&sbi->s_inode_lock);
INIT_LIST_HEAD(&sbi->s_dirty_files);
- INIT_LIST_HEAD(&sbi->s_list);
/*
* Following initialization is overlapped because
@@ -880,20 +892,11 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
if (err)
goto failed_sbi;
- if (nilfs_test_opt(sbi, SNAPSHOT)) {
- err = nilfs_attach_snapshot(sb, sbi->s_snapshot_cno,
- &sb->s_root);
- if (err)
- goto failed_sbi;
-
- goto add_to_supers;
- }
-
cno = nilfs_last_cno(nilfs);
err = nilfs_attach_checkpoint(sbi, cno, true, &fsroot);
if (err) {
- printk(KERN_ERR "NILFS: error loading a checkpoint"
- " (checkpoint number=%llu).\n", (unsigned long long)cno);
+ printk(KERN_ERR "NILFS: error loading last checkpoint "
+ "(checkpoint number=%llu).\n", (unsigned long long)cno);
goto failed_sbi;
}
@@ -915,13 +918,6 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
up_write(&nilfs->ns_sem);
}
- add_to_supers:
- down_write(&nilfs->ns_super_sem);
- list_add(&sbi->s_list, &nilfs->ns_supers);
- if (!nilfs_test_opt(sbi, SNAPSHOT))
- nilfs->ns_current = sbi;
- up_write(&nilfs->ns_super_sem);
-
return 0;
failed_segctor:
@@ -933,7 +929,7 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
failed_sbi:
put_nilfs(nilfs);
sb->s_fs_info = NULL;
- nilfs_put_sbinfo(sbi);
+ kfree(sbi);
return err;
}
@@ -943,15 +939,12 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
struct the_nilfs *nilfs = sbi->s_nilfs;
unsigned long old_sb_flags;
struct nilfs_mount_options old_opts;
- int was_snapshot, err;
+ int err;
lock_kernel();
- down_write(&nilfs->ns_super_sem);
old_sb_flags = sb->s_flags;
old_opts.mount_opt = sbi->s_mount_opt;
- old_opts.snapshot_cno = sbi->s_snapshot_cno;
- was_snapshot = nilfs_test_opt(sbi, SNAPSHOT);
if (!parse_options(data, sb, 1)) {
err = -EINVAL;
@@ -960,11 +953,6 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
sb->s_flags = (sb->s_flags & ~MS_POSIXACL);
err = -EINVAL;
- if (was_snapshot && !(*flags & MS_RDONLY)) {
- printk(KERN_ERR "NILFS (device %s): cannot remount snapshot "
- "read/write.\n", sb->s_id);
- goto restore_opts;
- }
if (!nilfs_valid_fs(nilfs)) {
printk(KERN_WARNING "NILFS (device %s): couldn't "
@@ -1021,15 +1009,12 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
up_write(&nilfs->ns_sem);
}
out:
- up_write(&nilfs->ns_super_sem);
unlock_kernel();
return 0;
restore_opts:
sb->s_flags = old_sb_flags;
sbi->s_mount_opt = old_opts.mount_opt;
- sbi->s_snapshot_cno = old_opts.snapshot_cno;
- up_write(&nilfs->ns_super_sem);
unlock_kernel();
return err;
}
@@ -1084,18 +1069,14 @@ static int nilfs_identify(char *data, struct nilfs_super_data *sd)
static int nilfs_set_bdev_super(struct super_block *s, void *data)
{
- struct nilfs_super_data *sd = data;
-
- s->s_bdev = sd->bdev;
+ s->s_bdev = data;
s->s_dev = s->s_bdev->bd_dev;
return 0;
}
static int nilfs_test_bdev_super(struct super_block *s, void *data)
{
- struct nilfs_super_data *sd = data;
-
- return sd->sbi && s->s_fs_info == (void *)sd->sbi;
+ return (void *)s->s_bdev == data;
}
static int
@@ -1106,7 +1087,8 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
struct super_block *s;
fmode_t mode = FMODE_READ;
struct the_nilfs *nilfs;
- int err, need_to_close = 1;
+ struct dentry *root_dentry;
+ int err, s_new = false;
if (!(flags & MS_RDONLY))
mode |= FMODE_WRITE;
@@ -1115,12 +1097,6 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
if (IS_ERR(sd.bdev))
return PTR_ERR(sd.bdev);
- /*
- * To get mount instance using sget() vfs-routine, NILFS needs
- * much more information than normal filesystems to identify mount
- * instance. For snapshot mounts, not only a mount type (ro-mount
- * or rw-mount) but also a checkpoint number is required.
- */
sd.cno = 0;
sd.flags = flags;
if (nilfs_identify((char *)data, &sd)) {
@@ -1136,38 +1112,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
mutex_lock(&nilfs->ns_mount_mutex);
- if (!sd.cno) {
- /*
- * Check if an exclusive mount exists or not.
- * Snapshot mounts coexist with a current mount
- * (i.e. rw-mount or ro-mount), whereas rw-mount and
- * ro-mount are mutually exclusive.
- */
- down_read(&nilfs->ns_super_sem);
- if (nilfs->ns_current &&
- ((nilfs->ns_current->s_super->s_flags ^ flags)
- & MS_RDONLY)) {
- up_read(&nilfs->ns_super_sem);
- err = -EBUSY;
- goto failed_unlock;
- }
- up_read(&nilfs->ns_super_sem);
- }
-
- /*
- * Find existing nilfs_sb_info struct
- */
- sd.sbi = nilfs_find_sbinfo(nilfs, !(flags & MS_RDONLY), sd.cno);
-
- /*
- * Get super block instance holding the nilfs_sb_info struct.
- * A new instance is allocated if no existing mount is present or
- * existing instance has been unmounted.
- */
- s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
- if (sd.sbi)
- nilfs_put_sbinfo(sd.sbi);
-
+ s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, sd.bdev);
if (IS_ERR(s)) {
err = PTR_ERR(s);
goto failed_unlock;
@@ -1176,6 +1121,8 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
if (!s->s_root) {
char b[BDEVNAME_SIZE];
+ s_new = true;
+
/* New superblock instance created */
s->s_flags = flags;
s->s_mode = mode;
@@ -1188,16 +1135,53 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
goto cancel_new;
s->s_flags |= MS_ACTIVE;
- need_to_close = 0;
+ } else if (!sd.cno) {
+ int busy = false;
+
+ if (nilfs_tree_was_touched(s->s_root)) {
+ busy = nilfs_try_to_shrink_tree(s->s_root);
+ if (busy && (flags ^ s->s_flags) & MS_RDONLY) {
+ printk(KERN_ERR "NILFS: the device already "
+ "has a %s mount.\n",
+ (s->s_flags & MS_RDONLY) ?
+ "read-only" : "read/write");
+ err = -EBUSY;
+ goto failed_super;
+ }
+ }
+ if (!busy) {
+ /*
+ * Try remount to setup mount states if the current
+ * tree is not mounted and only snapshots use this sb.
+ */
+ err = nilfs_remount(s, &flags, data);
+ if (err)
+ goto failed_super;
+ }
+ }
+
+ if (sd.cno) {
+ err = nilfs_attach_snapshot(s, sd.cno, &root_dentry);
+ if (err) {
+ if (s_new)
+ goto cancel_new;
+ goto failed_super;
+ }
+ } else {
+ root_dentry = dget(s->s_root);
}
mutex_unlock(&nilfs->ns_mount_mutex);
put_nilfs(nilfs);
- if (need_to_close)
+ if (!s_new)
close_bdev_exclusive(sd.bdev, mode);
- simple_set_mnt(mnt, s);
+
+ mnt->mnt_sb = s;
+ mnt->mnt_root = root_dentry;
return 0;
+ failed_super:
+ deactivate_locked_super(s);
failed_unlock:
mutex_unlock(&nilfs->ns_mount_mutex);
put_nilfs(nilfs);
@@ -1212,7 +1196,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
put_nilfs(nilfs);
deactivate_locked_super(s);
/*
- * deactivate_locked_super() invokes close_bdev_exclusive().
+ * This deactivate_locked_super() invokes close_bdev_exclusive().
* We must finish all post-cleaning before this call;
* put_nilfs() needs the block device.
*/
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 3bb1579..e8d950d 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -82,11 +82,9 @@ static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
atomic_set(&nilfs->ns_count, 1);
atomic_set(&nilfs->ns_ndirtyblks, 0);
init_rwsem(&nilfs->ns_sem);
- init_rwsem(&nilfs->ns_super_sem);
mutex_init(&nilfs->ns_mount_mutex);
init_rwsem(&nilfs->ns_writer_sem);
INIT_LIST_HEAD(&nilfs->ns_list);
- INIT_LIST_HEAD(&nilfs->ns_supers);
INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
spin_lock_init(&nilfs->ns_last_segment_lock);
nilfs->ns_cptree = RB_ROOT;
@@ -307,15 +305,6 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
int valid_fs = nilfs_valid_fs(nilfs);
int err;
- if (nilfs_loaded(nilfs)) {
- if (valid_fs ||
- ((s_flags & MS_RDONLY) && nilfs_test_opt(sbi, NORECOVERY)))
- return 0;
- printk(KERN_ERR "NILFS: the filesystem is in an incomplete "
- "recovery state.\n");
- return -EINVAL;
- }
-
if (!valid_fs) {
printk(KERN_WARNING "NILFS warning: mounting unchecked fs\n");
if (s_flags & MS_RDONLY) {
@@ -632,12 +621,7 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs,
*
* init_nilfs() performs common initialization per block device (e.g.
* reading the super block, getting disk layout information, initializing
- * shared fields in the_nilfs). It takes on some portion of the jobs
- * typically done by a fill_super() routine. This division arises from
- * the nature that multiple NILFS instances may be simultaneously
- * mounted on a device.
- * For multiple mounts on the same device, only the first mount
- * invokes these tasks.
+ * shared fields in the_nilfs).
*
* Return Value: On success, 0 is returned. On error, a negative error
* code is returned.
@@ -651,27 +635,6 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
int err;
down_write(&nilfs->ns_sem);
- if (nilfs_init(nilfs)) {
- /* Load values from existing the_nilfs */
- sbp = nilfs->ns_sbp[0];
- err = nilfs_store_magic_and_option(sb, sbp, data);
- if (err)
- goto out;
-
- err = nilfs_check_feature_compatibility(sb, sbp);
- if (err)
- goto out;
-
- blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
- if (sb->s_blocksize != blocksize &&
- !sb_set_blocksize(sb, blocksize)) {
- printk(KERN_ERR "NILFS: blocksize %d unfit to device\n",
- blocksize);
- err = -EINVAL;
- }
- sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);
- goto out;
- }
blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
if (!blocksize) {
@@ -901,56 +864,6 @@ void nilfs_put_root(struct nilfs_root *root)
}
}
-/**
- * nilfs_find_sbinfo - find existing nilfs_sb_info structure
- * @nilfs: nilfs object
- * @rw_mount: mount type (non-zero value for read/write mount)
- * @cno: checkpoint number (zero for read-only mount)
- *
- * nilfs_find_sbinfo() returns the nilfs_sb_info structure which
- * @rw_mount and @cno (in case of snapshots) matched. If no instance
- * was found, NULL is returned. Although the super block instance can
- * be unmounted after this function returns, the nilfs_sb_info struct
- * is kept on memory until nilfs_put_sbinfo() is called.
- */
-struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *nilfs,
- int rw_mount, __u64 cno)
-{
- struct nilfs_sb_info *sbi;
-
- down_read(&nilfs->ns_super_sem);
- /*
- * The SNAPSHOT flag and sb->s_flags are supposed to be
- * protected with nilfs->ns_super_sem.
- */
- sbi = nilfs->ns_current;
- if (rw_mount) {
- if (sbi && !(sbi->s_super->s_flags & MS_RDONLY))
- goto found; /* read/write mount */
- else
- goto out;
- } else if (cno == 0) {
- if (sbi && (sbi->s_super->s_flags & MS_RDONLY))
- goto found; /* read-only mount */
- else
- goto out;
- }
-
- list_for_each_entry(sbi, &nilfs->ns_supers, s_list) {
- if (nilfs_test_opt(sbi, SNAPSHOT) &&
- sbi->s_snapshot_cno == cno)
- goto found; /* snapshot mount */
- }
- out:
- up_read(&nilfs->ns_super_sem);
- return NULL;
-
- found:
- atomic_inc(&sbi->s_count);
- up_read(&nilfs->ns_super_sem);
- return sbi;
-}
-
int nilfs_checkpoint_is_mounted(struct the_nilfs *nilfs, __u64 cno,
int snapshot_mount)
{
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index 0afede6..7b43693 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -52,16 +52,13 @@ enum {
* @ns_bdi: backing dev info
* @ns_writer: back pointer to writable nilfs_sb_info
* @ns_sem: semaphore for shared states
- * @ns_super_sem: semaphore for global operations across super block instances
* @ns_mount_mutex: mutex protecting mount process of nilfs
* @ns_writer_sem: semaphore protecting ns_writer attach/detach
- * @ns_current: back pointer to current mount
* @ns_sbh: buffer heads of on-disk super blocks
* @ns_sbp: pointers to super block data
* @ns_sbwtime: previous write time of super block
* @ns_sbwcount: write count of super block
* @ns_sbsize: size of valid data in super block
- * @ns_supers: list of nilfs super block structs
* @ns_seg_seq: segment sequence counter
* @ns_segnum: index number of the latest full segment.
* @ns_nextnum: index number of the full segment index to be used next
@@ -104,17 +101,10 @@ struct the_nilfs {
struct backing_dev_info *ns_bdi;
struct nilfs_sb_info *ns_writer;
struct rw_semaphore ns_sem;
- struct rw_semaphore ns_super_sem;
struct mutex ns_mount_mutex;
struct rw_semaphore ns_writer_sem;
/*
- * components protected by ns_super_sem
- */
- struct nilfs_sb_info *ns_current;
- struct list_head ns_supers;
-
- /*
* used for
* - loading the latest checkpoint exclusively.
* - allocating a new full segment.
@@ -294,12 +284,6 @@ nilfs_detach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
up_write(&nilfs->ns_writer_sem);
}
-static inline void nilfs_put_sbinfo(struct nilfs_sb_info *sbi)
-{
- if (atomic_dec_and_test(&sbi->s_count))
- kfree(sbi);
-}
-
static inline int nilfs_valid_fs(struct the_nilfs *nilfs)
{
unsigned valid_fs;
--
1.6.6.2
--
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