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author | Al Viro <viro@zeniv.linux.org.uk> | 2009-05-06 01:07:50 -0400 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2009-05-09 10:49:39 -0400 |
commit | 74dbbdd7fdc11763f4698d2f3e684cf4446951e6 (patch) | |
tree | f31d70174915b0d209fafeec35e996e8ed7e269d /fs/super.c | |
parent | 677c9b2e393a0cd203bd54e9c18b012b2c73305a (diff) | |
download | kernel_samsung_smdk4412-74dbbdd7fdc11763f4698d2f3e684cf4446951e6.zip kernel_samsung_smdk4412-74dbbdd7fdc11763f4698d2f3e684cf4446951e6.tar.gz kernel_samsung_smdk4412-74dbbdd7fdc11763f4698d2f3e684cf4446951e6.tar.bz2 |
New helper: deactivate_locked_super()
Does equivalent of up_write(&s->s_umount); deactivate_super(s);
However, it does not does not unlock it until it's all over.
As the result, it's safe to use to dispose of new superblock on ->get_sb()
failure exits - nobody will see the sucker until it's all over.
Equivalent using up_write/deactivate_super is safe for that purpose
if superblock is either safe to use or has NULL ->s_root when we unlock.
Normally filesystems take the required precautions, but
a) we do have bugs in that area in some of them.
b) up_write/deactivate_super sequence is extremely common,
so the helper makes sense anyway.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/super.c')
-rw-r--r-- | fs/super.c | 46 |
1 files changed, 34 insertions, 12 deletions
@@ -208,6 +208,34 @@ void deactivate_super(struct super_block *s) EXPORT_SYMBOL(deactivate_super); /** + * deactivate_locked_super - drop an active reference to superblock + * @s: superblock to deactivate + * + * Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that + * it does not unlock it until it's all over. As the result, it's safe to + * use to dispose of new superblock on ->get_sb() failure exits - nobody + * will see the sucker until it's all over. Equivalent using up_write + + * deactivate_super is safe for that purpose only if superblock is either + * safe to use or has NULL ->s_root when we unlock. + */ +void deactivate_locked_super(struct super_block *s) +{ + struct file_system_type *fs = s->s_type; + if (atomic_dec_and_lock(&s->s_active, &sb_lock)) { + s->s_count -= S_BIAS-1; + spin_unlock(&sb_lock); + vfs_dq_off(s, 0); + fs->kill_sb(s); + put_filesystem(fs); + put_super(s); + } else { + up_write(&s->s_umount); + } +} + +EXPORT_SYMBOL(deactivate_locked_super); + +/** * grab_super - acquire an active reference * @s: reference we are trying to make active * @@ -797,8 +825,7 @@ int get_sb_ns(struct file_system_type *fs_type, int flags, void *data, sb->s_flags = flags; err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0); if (err) { - up_write(&sb->s_umount); - deactivate_super(sb); + deactivate_locked_super(sb); return err; } @@ -854,8 +881,7 @@ int get_sb_bdev(struct file_system_type *fs_type, if (s->s_root) { if ((flags ^ s->s_flags) & MS_RDONLY) { - up_write(&s->s_umount); - deactivate_super(s); + deactivate_locked_super(s); error = -EBUSY; goto error_bdev; } @@ -870,8 +896,7 @@ int get_sb_bdev(struct file_system_type *fs_type, sb_set_blocksize(s, block_size(bdev)); error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { - up_write(&s->s_umount); - deactivate_super(s); + deactivate_locked_super(s); goto error; } @@ -921,8 +946,7 @@ int get_sb_nodev(struct file_system_type *fs_type, error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { - up_write(&s->s_umount); - deactivate_super(s); + deactivate_locked_super(s); return error; } s->s_flags |= MS_ACTIVE; @@ -952,8 +976,7 @@ int get_sb_single(struct file_system_type *fs_type, s->s_flags = flags; error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { - up_write(&s->s_umount); - deactivate_super(s); + deactivate_locked_super(s); return error; } s->s_flags |= MS_ACTIVE; @@ -1006,8 +1029,7 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void return mnt; out_sb: dput(mnt->mnt_root); - up_write(&mnt->mnt_sb->s_umount); - deactivate_super(mnt->mnt_sb); + deactivate_locked_super(mnt->mnt_sb); out_free_secdata: free_secdata(secdata); out_mnt: |