nilfs2: fix circular locking dependency of writer mutex
This fixes the following circular locking dependency problem: ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.30-rc3 #5 ------------------------------------------------------- segctord/3895 is trying to acquire lock: (&nilfs->ns_writer_mutex){+.+...}, at: [<d0d02172>] nilfs_mdt_get_block+0x89/0x20f [nilfs2] but task is already holding lock: (&bmap->b_sem){++++..}, at: [<d0d02d99>] nilfs_bmap_propagate+0x14/0x2e [nilfs2] which lock already depends on the new lock. The bugfix is done by replacing call sites of nilfs_get_writer() which are never called from read-only context with direct dereferencing of pointer to a writable FS-instance. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
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85c2a74fab
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201913ed74
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@ -516,14 +516,16 @@ static ssize_t
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nilfs_ioctl_do_free_segments(struct the_nilfs *nilfs, __u64 *posp, int flags,
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nilfs_ioctl_do_free_segments(struct the_nilfs *nilfs, __u64 *posp, int flags,
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void *buf, size_t size, size_t nmembs)
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void *buf, size_t size, size_t nmembs)
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{
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{
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struct nilfs_sb_info *sbi = nilfs_get_writer(nilfs);
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struct nilfs_sb_info *sbi = nilfs->ns_writer;
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int ret;
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int ret;
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if (unlikely(!sbi))
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if (unlikely(!sbi)) {
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/* never happens because called for a writable mount */
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WARN_ON(1);
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return -EROFS;
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return -EROFS;
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}
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ret = nilfs_segctor_add_segments_to_be_freed(
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ret = nilfs_segctor_add_segments_to_be_freed(
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NILFS_SC(sbi), buf, nmembs);
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NILFS_SC(sbi), buf, nmembs);
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nilfs_put_writer(nilfs);
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return (ret < 0) ? ret : nmembs;
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return (ret < 0) ? ret : nmembs;
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}
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}
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@ -77,19 +77,22 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
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void *))
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void *))
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{
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{
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struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs;
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struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs;
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struct nilfs_sb_info *writer = NULL;
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struct super_block *sb = inode->i_sb;
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struct super_block *sb = inode->i_sb;
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struct nilfs_transaction_info ti;
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struct nilfs_transaction_info ti;
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struct buffer_head *bh;
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struct buffer_head *bh;
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int err;
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int err;
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if (!sb) {
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if (!sb) {
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writer = nilfs_get_writer(nilfs);
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/*
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if (!writer) {
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* Make sure this function is not called from any
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* read-only context.
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*/
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if (!nilfs->ns_writer) {
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WARN_ON(1);
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err = -EROFS;
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err = -EROFS;
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goto out;
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goto out;
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}
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}
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sb = writer->s_super;
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sb = nilfs->ns_writer->s_super;
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}
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}
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nilfs_transaction_begin(sb, &ti, 0);
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nilfs_transaction_begin(sb, &ti, 0);
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@ -127,8 +130,6 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
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err = nilfs_transaction_commit(sb);
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err = nilfs_transaction_commit(sb);
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else
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else
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nilfs_transaction_abort(sb);
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nilfs_transaction_abort(sb);
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if (writer)
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nilfs_put_writer(nilfs);
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out:
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out:
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return err;
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return err;
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}
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}
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