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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2015-02-05 12:25:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-05 13:35:29 -0800
commit7ef3ff2fea8bf5e4a21cef47ad87710a3d0fdb52 (patch)
treefae90c5009ed6bf5009cedf9646c0a4edd71304c /fs/nilfs2/segment.h
parent81cca6fb1271b91f06b008976ea132bec2f14d86 (diff)
downloadlinux-7ef3ff2fea8bf5e4a21cef47ad87710a3d0fdb52.tar.bz2
nilfs2: fix deadlock of segment constructor over I_SYNC flag
Nilfs2 eventually hangs in a stress test with fsstress program. This issue was caused by the following deadlock over I_SYNC flag between nilfs_segctor_thread() and writeback_sb_inodes(): nilfs_segctor_thread() nilfs_segctor_thread_construct() nilfs_segctor_unlock() nilfs_dispose_list() iput() iput_final() evict() inode_wait_for_writeback() * wait for I_SYNC flag writeback_sb_inodes() * set I_SYNC flag on inode->i_state __writeback_single_inode() do_writepages() nilfs_writepages() nilfs_construct_dsync_segment() nilfs_segctor_sync() * wait for completion of segment constructor inode_sync_complete() * clear I_SYNC flag after __writeback_single_inode() completed writeback_sb_inodes() calls do_writepages() for dirty inodes after setting I_SYNC flag on inode->i_state. do_writepages() in turn calls nilfs_writepages(), which can run segment constructor and wait for its completion. On the other hand, segment constructor calls iput(), which can call evict() and wait for the I_SYNC flag on inode_wait_for_writeback(). Since segment constructor doesn't know when I_SYNC will be set, it cannot know whether iput() will block or not unless inode->i_nlink has a non-zero count. We can prevent evict() from being called in iput() by implementing sop->drop_inode(), but it's not preferable to leave inodes with i_nlink == 0 for long periods because it even defers file truncation and inode deallocation. So, this instead resolves the deadlock by calling iput() asynchronously with a workqueue for inodes with i_nlink == 0. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/nilfs2/segment.h')
-rw-r--r--fs/nilfs2/segment.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/nilfs2/segment.h b/fs/nilfs2/segment.h
index 38a1d0013314..a48d6de1e02c 100644
--- a/fs/nilfs2/segment.h
+++ b/fs/nilfs2/segment.h
@@ -26,6 +26,7 @@
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
+#include <linux/workqueue.h>
#include <linux/nilfs2_fs.h>
#include "nilfs.h"
@@ -92,6 +93,8 @@ struct nilfs_segsum_pointer {
* @sc_nblk_inc: Block count of current generation
* @sc_dirty_files: List of files to be written
* @sc_gc_inodes: List of GC inodes having blocks to be written
+ * @sc_iput_queue: list of inodes for which iput should be done
+ * @sc_iput_work: work struct to defer iput call
* @sc_freesegs: array of segment numbers to be freed
* @sc_nfreesegs: number of segments on @sc_freesegs
* @sc_dsync_inode: inode whose data pages are written for a sync operation
@@ -135,6 +138,8 @@ struct nilfs_sc_info {
struct list_head sc_dirty_files;
struct list_head sc_gc_inodes;
+ struct list_head sc_iput_queue;
+ struct work_struct sc_iput_work;
__u64 *sc_freesegs;
size_t sc_nfreesegs;