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nilfs2: fix the nilfs_iget() vs. nilfs_new_inode() races
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Same story as in commit 41080b5 ("nfsd race fixes: ext2") (similar
ext2 fix) except that nilfs2 needs to use insert_inode_locked4() instead
of insert_inode_locked() and a bug of a check for dead inodes needs to
be fixed.

If nilfs_iget() is called from nfsd after nilfs_new_inode() calls
insert_inode_locked4(), nilfs_iget() will wait for unlock_new_inode() at
the end of nilfs_mkdir()/nilfs_create()/etc to unlock the inode.

If nilfs_iget() is called before nilfs_new_inode() calls
insert_inode_locked4(), it will create an in-core inode and read its
data from the on-disk inode.  But, nilfs_iget() will find i_nlink equals
zero and fail at nilfs_read_inode_common(), which will lead it to call
iget_failed() and cleanly fail.

However, this sanity check doesn't work as expected for reused on-disk
inodes because they leave a non-zero value in i_mode field and it
hinders the test of i_nlink.  This patch also fixes the issue by
removing the test on i_mode that nilfs2 doesn't need.

Signed-off-by: Ryusuke Konishi <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@konis @torvalds
konis authored and torvalds committed Dec 11, 2014
1 parent 72b9918 commit 705304a
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Showing 2 changed files with 36 additions and 11 deletions.
32 changes: 24 additions & 8 deletions fs/nilfs2/inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,8 @@ struct nilfs_iget_args {
int for_gc;
};

static int nilfs_iget_test(struct inode *inode, void *opaque);

void nilfs_inode_add_blocks(struct inode *inode, int n)
{
struct nilfs_root *root = NILFS_I(inode)->i_root;
Expand Down Expand Up @@ -348,6 +350,17 @@ const struct address_space_operations nilfs_aops = {
.is_partially_uptodate = block_is_partially_uptodate,
};

static int nilfs_insert_inode_locked(struct inode *inode,
struct nilfs_root *root,
unsigned long ino)
{
struct nilfs_iget_args args = {
.ino = ino, .root = root, .cno = 0, .for_gc = 0
};

return insert_inode_locked4(inode, ino, nilfs_iget_test, &args);
}

struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
{
struct super_block *sb = dir->i_sb;
Expand Down Expand Up @@ -383,7 +396,7 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
if (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)) {
err = nilfs_bmap_read(ii->i_bmap, NULL);
if (err < 0)
goto failed_bmap;
goto failed_after_creation;

set_bit(NILFS_I_BMAP, &ii->i_state);
/* No lock is needed; iget() ensures it. */
Expand All @@ -399,21 +412,24 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
spin_lock(&nilfs->ns_next_gen_lock);
inode->i_generation = nilfs->ns_next_generation++;
spin_unlock(&nilfs->ns_next_gen_lock);
insert_inode_hash(inode);
if (nilfs_insert_inode_locked(inode, root, ino) < 0) {
err = -EIO;
goto failed_after_creation;
}

err = nilfs_init_acl(inode, dir);
if (unlikely(err))
goto failed_acl; /* never occur. When supporting
goto failed_after_creation; /* never occur. When supporting
nilfs_init_acl(), proper cancellation of
above jobs should be considered */

return inode;

failed_acl:
failed_bmap:
failed_after_creation:
clear_nlink(inode);
unlock_new_inode(inode);
iput(inode); /* raw_inode will be deleted through
generic_delete_inode() */
nilfs_evict_inode() */
goto failed;

failed_ifile_create_inode:
Expand Down Expand Up @@ -461,8 +477,8 @@ int nilfs_read_inode_common(struct inode *inode,
inode->i_atime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
inode->i_ctime.tv_nsec = le32_to_cpu(raw_inode->i_ctime_nsec);
inode->i_mtime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
if (inode->i_nlink == 0 && inode->i_mode == 0)
return -EINVAL; /* this inode is deleted */
if (inode->i_nlink == 0)
return -ESTALE; /* this inode is deleted */

inode->i_blocks = le64_to_cpu(raw_inode->i_blocks);
ii->i_flags = le32_to_cpu(raw_inode->i_flags);
Expand Down
15 changes: 12 additions & 3 deletions fs/nilfs2/namei.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,9 +51,11 @@ static inline int nilfs_add_nondir(struct dentry *dentry, struct inode *inode)
int err = nilfs_add_link(dentry, inode);
if (!err) {
d_instantiate(dentry, inode);
unlock_new_inode(inode);
return 0;
}
inode_dec_link_count(inode);
unlock_new_inode(inode);
iput(inode);
return err;
}
Expand Down Expand Up @@ -182,6 +184,7 @@ static int nilfs_symlink(struct inode *dir, struct dentry *dentry,
out_fail:
drop_nlink(inode);
nilfs_mark_inode_dirty(inode);
unlock_new_inode(inode);
iput(inode);
goto out;
}
Expand All @@ -201,11 +204,15 @@ static int nilfs_link(struct dentry *old_dentry, struct inode *dir,
inode_inc_link_count(inode);
ihold(inode);

err = nilfs_add_nondir(dentry, inode);
if (!err)
err = nilfs_add_link(dentry, inode);
if (!err) {
d_instantiate(dentry, inode);
err = nilfs_transaction_commit(dir->i_sb);
else
} else {
inode_dec_link_count(inode);
iput(inode);
nilfs_transaction_abort(dir->i_sb);
}

return err;
}
Expand Down Expand Up @@ -243,6 +250,7 @@ static int nilfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)

nilfs_mark_inode_dirty(inode);
d_instantiate(dentry, inode);
unlock_new_inode(inode);
out:
if (!err)
err = nilfs_transaction_commit(dir->i_sb);
Expand All @@ -255,6 +263,7 @@ static int nilfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
drop_nlink(inode);
drop_nlink(inode);
nilfs_mark_inode_dirty(inode);
unlock_new_inode(inode);
iput(inode);
out_dir:
drop_nlink(dir);
Expand Down

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