nilfs2: get rid of sget use for acquiring nilfs object
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 <konishi.ryusuke@lab.ntt.co.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Ryusuke Konishi
Al Viro
Родитель
81fc20bd0e
Коммит
33c8e57c86
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@ -1059,13 +1059,6 @@ static int nilfs_set_bdev_super(struct super_block *s, void *data)
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}
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static int nilfs_test_bdev_super(struct super_block *s, void *data)
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{
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struct nilfs_super_data *sd = data;
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return s->s_bdev == sd->bdev;
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}
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static int nilfs_test_bdev_super2(struct super_block *s, void *data)
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{
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struct nilfs_super_data *sd = data;
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int ret;
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@ -1096,8 +1089,8 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
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const char *dev_name, void *data, struct vfsmount *mnt)
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{
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struct nilfs_super_data sd;
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struct super_block *s, *s2;
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struct the_nilfs *nilfs = NULL;
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struct super_block *s;
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struct the_nilfs *nilfs;
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int err, need_to_close = 1;
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sd.bdev = open_bdev_exclusive(dev_name, flags, fs_type);
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@ -1118,11 +1111,12 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
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goto failed;
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}
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/*
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* once the super is inserted into the list by sget, s_umount
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* will protect the lockfs code from trying to start a snapshot
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* while we are mounting
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*/
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nilfs = find_or_create_nilfs(sd.bdev);
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if (!nilfs) {
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err = -ENOMEM;
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goto failed;
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}
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down(&sd.bdev->bd_mount_sem);
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if (!sd.cno &&
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(err = test_exclusive_mount(fs_type, sd.bdev, flags ^ MS_RDONLY))) {
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@ -1131,51 +1125,22 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
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}
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/*
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* Phase-1: search any existent instance and get the_nilfs
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* Search specified snapshot or R/W mode super_block
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*/
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if (!sd.cno)
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/* trying to get the latest checkpoint. */
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sd.cno = nilfs_last_cno(nilfs);
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s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
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if (IS_ERR(s))
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goto error_s;
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if (!s->s_root) {
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err = -ENOMEM;
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nilfs = alloc_nilfs(sd.bdev);
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if (!nilfs)
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goto cancel_new;
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} else {
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struct nilfs_sb_info *sbi = NILFS_SB(s);
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/*
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* s_umount protects super_block from unmount process;
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* It covers pointers of nilfs_sb_info and the_nilfs.
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*/
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nilfs = sbi->s_nilfs;
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get_nilfs(nilfs);
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up_write(&s->s_umount);
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/*
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* Phase-2: search specified snapshot or R/W mode super_block
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*/
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if (!sd.cno)
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/* trying to get the latest checkpoint. */
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sd.cno = nilfs_last_cno(nilfs);
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s2 = sget(fs_type, nilfs_test_bdev_super2,
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nilfs_set_bdev_super, &sd);
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deactivate_super(s);
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/*
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* Although deactivate_super() invokes close_bdev_exclusive() at
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* kill_block_super(). Here, s is an existent mount; we need
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* one more close_bdev_exclusive() call.
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*/
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s = s2;
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if (IS_ERR(s))
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goto error_s;
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if (IS_ERR(s)) {
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err = PTR_ERR(s);
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goto failed_unlock;
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}
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if (!s->s_root) {
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char b[BDEVNAME_SIZE];
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/* New superblock instance created */
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s->s_flags = flags;
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strlcpy(s->s_id, bdevname(sd.bdev, b), sizeof(s->s_id));
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sb_set_blocksize(s, block_size(sd.bdev));
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@ -1195,15 +1160,9 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
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simple_set_mnt(mnt, s);
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return 0;
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error_s:
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up(&sd.bdev->bd_mount_sem);
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if (nilfs)
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put_nilfs(nilfs);
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close_bdev_exclusive(sd.bdev, flags);
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return PTR_ERR(s);
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failed_unlock:
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up(&sd.bdev->bd_mount_sem);
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put_nilfs(nilfs);
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failed:
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close_bdev_exclusive(sd.bdev, flags);
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@ -1212,8 +1171,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
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cancel_new:
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/* Abandoning the newly allocated superblock */
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up(&sd.bdev->bd_mount_sem);
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if (nilfs)
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put_nilfs(nilfs);
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put_nilfs(nilfs);
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up_write(&s->s_umount);
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deactivate_super(s);
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/*
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@ -35,6 +35,10 @@
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#include "seglist.h"
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#include "segbuf.h"
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static LIST_HEAD(nilfs_objects);
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static DEFINE_SPINLOCK(nilfs_lock);
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void nilfs_set_last_segment(struct the_nilfs *nilfs,
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sector_t start_blocknr, u64 seq, __u64 cno)
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{
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@ -55,7 +59,7 @@ void nilfs_set_last_segment(struct the_nilfs *nilfs,
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* Return Value: On success, pointer to the_nilfs is returned.
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* On error, NULL is returned.
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*/
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struct the_nilfs *alloc_nilfs(struct block_device *bdev)
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static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
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{
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struct the_nilfs *nilfs;
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@ -69,6 +73,7 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
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atomic_set(&nilfs->ns_ndirtyblks, 0);
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init_rwsem(&nilfs->ns_sem);
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mutex_init(&nilfs->ns_writer_mutex);
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INIT_LIST_HEAD(&nilfs->ns_list);
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INIT_LIST_HEAD(&nilfs->ns_supers);
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spin_lock_init(&nilfs->ns_last_segment_lock);
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nilfs->ns_gc_inodes_h = NULL;
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@ -77,6 +82,45 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
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return nilfs;
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}
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/**
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* find_or_create_nilfs - find or create nilfs object
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* @bdev: block device to which the_nilfs is related
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*
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* find_nilfs() looks up an existent nilfs object created on the
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* device and gets the reference count of the object. If no nilfs object
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* is found on the device, a new nilfs object is allocated.
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*
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* Return Value: On success, pointer to the nilfs object is returned.
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* On error, NULL is returned.
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*/
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struct the_nilfs *find_or_create_nilfs(struct block_device *bdev)
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{
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struct the_nilfs *nilfs, *new = NULL;
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retry:
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spin_lock(&nilfs_lock);
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list_for_each_entry(nilfs, &nilfs_objects, ns_list) {
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if (nilfs->ns_bdev == bdev) {
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get_nilfs(nilfs);
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spin_unlock(&nilfs_lock);
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if (new)
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put_nilfs(new);
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return nilfs; /* existing object */
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}
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}
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if (new) {
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list_add_tail(&new->ns_list, &nilfs_objects);
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spin_unlock(&nilfs_lock);
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return new; /* new object */
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}
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spin_unlock(&nilfs_lock);
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new = alloc_nilfs(bdev);
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if (new)
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goto retry;
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return NULL; /* insufficient memory */
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}
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/**
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* put_nilfs - release a reference to the_nilfs
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* @nilfs: the_nilfs structure to be released
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@ -86,13 +130,20 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
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*/
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void put_nilfs(struct the_nilfs *nilfs)
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{
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if (!atomic_dec_and_test(&nilfs->ns_count))
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spin_lock(&nilfs_lock);
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if (!atomic_dec_and_test(&nilfs->ns_count)) {
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spin_unlock(&nilfs_lock);
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return;
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}
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list_del_init(&nilfs->ns_list);
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spin_unlock(&nilfs_lock);
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/*
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* Increment of ns_count never occur below because the caller
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* Increment of ns_count never occurs below because the caller
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* of get_nilfs() holds at least one reference to the_nilfs.
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* Thus its exclusion control is not required here.
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*/
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might_sleep();
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if (nilfs_loaded(nilfs)) {
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nilfs_mdt_clear(nilfs->ns_sufile);
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@ -43,6 +43,7 @@ enum {
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* struct the_nilfs - struct to supervise multiple nilfs mount points
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* @ns_flags: flags
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* @ns_count: reference count
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* @ns_list: list head for nilfs_list
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* @ns_bdev: block device
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* @ns_bdi: backing dev info
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* @ns_writer: back pointer to writable nilfs_sb_info
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@ -88,6 +89,7 @@ enum {
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struct the_nilfs {
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unsigned long ns_flags;
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atomic_t ns_count;
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struct list_head ns_list;
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struct block_device *ns_bdev;
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struct backing_dev_info *ns_bdi;
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@ -191,7 +193,7 @@ THE_NILFS_FNS(DISCONTINUED, discontinued)
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#define NILFS_ALTSB_FREQ 60 /* spare superblock */
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void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
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struct the_nilfs *alloc_nilfs(struct block_device *);
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struct the_nilfs *find_or_create_nilfs(struct block_device *);
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void put_nilfs(struct the_nilfs *);
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int init_nilfs(struct the_nilfs *, struct nilfs_sb_info *, char *);
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int load_nilfs(struct the_nilfs *, struct nilfs_sb_info *);
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