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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-04-28 21:04:59 +0900
committerRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-05-09 13:36:57 +0900
commit201913ed746c7724a40d33ee5a0b6a1fd2ef3193 (patch)
tree149cd7552a854055a2ed278234649a77914aaf96
parent85c2a74fabadfc561b75fbd7decc6bcbfe873d57 (diff)
downloadlinux-201913ed746c7724a40d33ee5a0b6a1fd2ef3193.tar.gz
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>
-rw-r--r--fs/nilfs2/ioctl.c8
-rw-r--r--fs/nilfs2/mdt.c13
2 files changed, 12 insertions, 9 deletions
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 108d281ebca..be387c6b2d4 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 47dd815433f..e1c6777931b 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;
}