From 201913ed746c7724a40d33ee5a0b6a1fd2ef3193 Mon Sep 17 00:00:00 2001 From: Ryusuke Konishi Date: Tue, 28 Apr 2009 21:04:59 +0900 Subject: [PATCH] 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: [] nilfs_mdt_get_block+0x89/0x20f [nilfs2] but task is already holding lock: (&bmap->b_sem){++++..}, at: [] 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 --- fs/nilfs2/ioctl.c | 8 +++++--- fs/nilfs2/mdt.c | 13 +++++++------ 2 files changed, 12 insertions(+), 9 deletions(-) diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c index 108d281ebca5..be387c6b2d46 100644 --- a/fs/nilfs2/ioctl.c +++ b/fs/nilfs2/ioctl.c @@ -516,14 +516,16 @@ static ssize_t nilfs_ioctl_do_free_segments(struct the_nilfs *nilfs, __u64 *posp, int flags, void *buf, size_t size, size_t nmembs) { - struct nilfs_sb_info *sbi = nilfs_get_writer(nilfs); + struct nilfs_sb_info *sbi = nilfs->ns_writer; int ret; - if (unlikely(!sbi)) + if (unlikely(!sbi)) { + /* never happens because called for a writable mount */ + WARN_ON(1); return -EROFS; + } ret = nilfs_segctor_add_segments_to_be_freed( NILFS_SC(sbi), buf, nmembs); - nilfs_put_writer(nilfs); return (ret < 0) ? ret : nmembs; } diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c index 47dd815433fd..e1c6777931b7 100644 --- a/fs/nilfs2/mdt.c +++ b/fs/nilfs2/mdt.c @@ -77,19 +77,22 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block, void *)) { struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs; - struct nilfs_sb_info *writer = NULL; struct super_block *sb = inode->i_sb; struct nilfs_transaction_info ti; struct buffer_head *bh; int err; if (!sb) { - writer = nilfs_get_writer(nilfs); - if (!writer) { + /* + * Make sure this function is not called from any + * read-only context. + */ + if (!nilfs->ns_writer) { + WARN_ON(1); err = -EROFS; goto out; } - sb = writer->s_super; + sb = nilfs->ns_writer->s_super; } nilfs_transaction_begin(sb, &ti, 0); @@ -127,8 +130,6 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block, err = nilfs_transaction_commit(sb); else nilfs_transaction_abort(sb); - if (writer) - nilfs_put_writer(nilfs); out: return err; } -- 2.20.1