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Date: Wed, 13 Jul 2016 09:18:29 +0800
From: Chao Yu <yuchao0@...wei.com>
To: <jaegeuk@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>, Chao Yu <yuchao0@...wei.com>
Subject: [PATCH v4] f2fs: fix to avoid data update racing between GC and DIO
Datas in file can be operated by GC and DIO simultaneously, so we will
face race case as below:
For write case:
Thread A Thread B
- generic_file_direct_write
- invalidate_inode_pages2_range
- f2fs_direct_IO
- do_blockdev_direct_IO
- do_direct_IO
- get_more_blocks
- f2fs_gc
- do_garbage_collect
- gc_data_segment
- move_data_page
- do_write_data_page
migrate data block to new block address
- dio_bio_submit
update user data to old block address
For read case:
Thread A Thread B
- generic_file_direct_write
- invalidate_inode_pages2_range
- f2fs_direct_IO
- do_blockdev_direct_IO
- do_direct_IO
- get_more_blocks
- f2fs_balance_fs
- f2fs_gc
- do_garbage_collect
- gc_data_segment
- move_data_page
- do_write_data_page
migrate data block to new block address
- write_checkpoint
- do_checkpoint
- clear_prefree_segments
- f2fs_issue_discard
discard old block adress
- dio_bio_submit
update user buffer from obsolete block address
In order to fix this, for one file, we should let DIO and GC getting exclusion
against with each other.
Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
v4: split rwsem to avoid deadlock between dio reader and dio writer.
fs/f2fs/data.c | 6 +++++-
fs/f2fs/f2fs.h | 1 +
fs/f2fs/gc.c | 20 ++++++++++++++++++++
fs/f2fs/super.c | 2 ++
4 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 20b3016..62947c30 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1714,6 +1714,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
struct inode *inode = mapping->host;
size_t count = iov_iter_count(iter);
loff_t offset = iocb->ki_pos;
+ int rw = iov_iter_rw(iter);
int err;
err = check_direct_IO(inode, iter, offset);
@@ -1727,8 +1728,11 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
trace_f2fs_direct_IO_enter(inode, offset, count, iov_iter_rw(iter));
+ down_read(&F2FS_I(inode)->dio_rwsem[rw]);
err = blockdev_direct_IO(iocb, inode, iter, get_data_block_dio);
- if (iov_iter_rw(iter) == WRITE) {
+ up_read(&F2FS_I(inode)->dio_rwsem[rw]);
+
+ if (rw == WRITE) {
if (err > 0)
set_inode_flag(inode, FI_UPDATE_WRITE);
else if (err < 0)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 1190c04..5973759 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -474,6 +474,7 @@ struct f2fs_inode_info {
struct list_head inmem_pages; /* inmemory pages managed by f2fs */
struct mutex inmem_lock; /* lock for inmemory pages */
struct extent_tree *extent_tree; /* cached extent_tree entry */
+ struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */
};
static inline void get_extent_info(struct extent_info *ext,
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index c612137..5c8acf7 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -755,12 +755,32 @@ next_step:
/* phase 3 */
inode = find_gc_inode(gc_list, dni.ino);
if (inode) {
+ struct f2fs_inode_info *fi = F2FS_I(inode);
+ bool locked = false;
+
+ if (S_ISREG(inode->i_mode)) {
+ if (!down_write_trylock(&fi->dio_rwsem[READ]))
+ continue;
+ if (!down_write_trylock(
+ &fi->dio_rwsem[WRITE])) {
+ up_write(&fi->dio_rwsem[READ]);
+ continue;
+ }
+ locked = true;
+ }
+
start_bidx = start_bidx_of_node(nofs, inode)
+ ofs_in_node;
if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
move_encrypted_block(inode, start_bidx);
else
move_data_page(inode, start_bidx, gc_type);
+
+ if (locked) {
+ up_write(&fi->dio_rwsem[WRITE]);
+ up_write(&fi->dio_rwsem[READ]);
+ }
+
stat_inc_data_blk_count(sbi, 1, gc_type);
}
}
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 451dfb4..b97c065 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -579,6 +579,8 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
INIT_LIST_HEAD(&fi->gdirty_list);
INIT_LIST_HEAD(&fi->inmem_pages);
mutex_init(&fi->inmem_lock);
+ init_rwsem(&fi->dio_rwsem[READ]);
+ init_rwsem(&fi->dio_rwsem[WRITE]);
/* Will be used by directory only */
fi->i_dir_level = F2FS_SB(sb)->dir_level;
--
2.8.2.311.gee88674
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