This simplifies the test function passed on the remaining sget()
callsite in nilfs.
Instead of checking mount type (i.e. ro-mount/rw-mount/snapshot mount)
in the test function passed to sget(), this patch first looks up the
nilfs_sb_info struct which the given mount type matches, and then
acquires the super block instance holding the nilfs_sb_info.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/sb.h | 1 +
fs/nilfs2/super.c | 42 ++++++++++++++++------------------------
fs/nilfs2/the_nilfs.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
fs/nilfs2/the_nilfs.h | 7 ++++++
4 files changed, 75 insertions(+), 25 deletions(-)
diff --git a/fs/nilfs2/sb.h b/fs/nilfs2/sb.h
index adccd4f..0776ccc 100644
--- a/fs/nilfs2/sb.h
+++ b/fs/nilfs2/sb.h
@@ -60,6 +60,7 @@ struct nilfs_sb_info {
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 0a62901..7370bc5 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -330,7 +330,7 @@ static void nilfs_put_super(struct super_block *sb)
put_nilfs(sbi->s_nilfs);
sbi->s_super = NULL;
sb->s_fs_info = NULL;
- kfree(sbi);
+ nilfs_put_sbinfo(sbi);
}
/**
@@ -775,6 +775,7 @@ 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)
@@ -892,7 +893,7 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
failed_sbi:
put_nilfs(nilfs);
sb->s_fs_info = NULL;
- kfree(sbi);
+ nilfs_put_sbinfo(sbi);
return err;
}
@@ -1000,6 +1001,7 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
struct nilfs_super_data {
struct block_device *bdev;
+ struct nilfs_sb_info *sbi;
__u64 cno;
int flags;
};
@@ -1057,27 +1059,8 @@ 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;
- int ret;
-
- if (s->s_bdev != sd->bdev)
- return 0;
-
- if (!((s->s_flags | sd->flags) & MS_RDONLY))
- return 1; /* Reuse an old R/W-mode super_block */
-
- if (s->s_flags & sd->flags & MS_RDONLY) {
- if (down_read_trylock(&s->s_umount)) {
- ret = s->s_root &&
- (sd->cno == NILFS_SB(s)->s_snapshot_cno);
- up_read(&s->s_umount);
- /*
- * This path is locked with sb_lock by sget().
- * So, drop_super() causes deadlock.
- */
- return ret;
- }
- }
- return 0;
+
+ return sd->sbi && s->s_fs_info == (void *)sd->sbi;
}
static int
@@ -1098,7 +1081,6 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
* 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.
- * The results are passed in sget() using nilfs_super_data.
*/
sd.cno = 0;
sd.flags = flags;
@@ -1134,13 +1116,23 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
}
/*
- * Search specified snapshot or R/W mode super_block
+ * Find existing nilfs_sb_info struct
*/
+ sd.sbi = nilfs_find_sbinfo(nilfs, !(flags & MS_RDONLY), sd.cno);
+
if (!sd.cno)
/* trying to get the latest checkpoint. */
sd.cno = nilfs_last_cno(nilfs);
+ /*
+ * 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);
+
if (IS_ERR(s)) {
err = PTR_ERR(s);
goto failed_unlock;
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 92ff3b1..ff8600e 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -664,6 +664,56 @@ int nilfs_near_disk_full(struct the_nilfs *nilfs)
return ret;
}
+/**
+ * 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_sem);
+ /*
+ * The SNAPSHOT flag and sb->s_flags are supposed to be
+ * protected with nilfs->ns_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_sem);
+ return NULL;
+
+ found:
+ atomic_inc(&sbi->s_count);
+ up_read(&nilfs->ns_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 99f7e29..be4c040 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -201,6 +201,7 @@ 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 *);
int nilfs_count_free_blocks(struct the_nilfs *, sector_t *);
+struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *, int, __u64);
int nilfs_checkpoint_is_mounted(struct the_nilfs *, __u64, int);
int nilfs_near_disk_full(struct the_nilfs *);
void nilfs_fall_back_super_block(struct the_nilfs *);
@@ -243,6 +244,12 @@ nilfs_detach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
mutex_unlock(&nilfs->ns_writer_mutex);
}
+static inline void nilfs_put_sbinfo(struct nilfs_sb_info *sbi)
+{
+ if (!atomic_dec_and_test(&sbi->s_count))
+ kfree(sbi);
+}
+
static inline void
nilfs_get_segment_range(struct the_nilfs *nilfs, __u64 segnum,
sector_t *seg_start, sector_t *seg_end)
--
1.6.2
--
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