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Date: Wed, 30 Dec 2020 15:55:57 +0800
From: Chao Yu <yuchao0@...wei.com>
To: <jaegeuk@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>, <chao@...nel.org>,
Chao Yu <yuchao0@...wei.com>
Subject: [PATCH v2] f2fs: fix to keep isolation of atomic write
ThreadA ThreadB
- f2fs_ioc_start_atomic_write
- write
- f2fs_ioc_commit_atomic_write
- f2fs_commit_inmem_pages
- f2fs_drop_inmem_pages
- f2fs_drop_inmem_pages
- __revoke_inmem_pages
- f2fs_vm_page_mkwrite
- set_page_dirty
- tag ATOMIC_WRITTEN_PAGE and add page
to inmem_pages list
- clear_inode_flag(FI_ATOMIC_FILE)
- f2fs_vm_page_mkwrite
- set_page_dirty
- f2fs_update_dirty_page
- f2fs_trace_pid
- tag inmem page private to pid
- truncate
- f2fs_invalidate_page
- set page->mapping to NULL
then it will cause panic once we
access page->mapping
The root cause is we missed to keep isolation of atomic write in the case
of commit_atomic_write vs mkwrite, let commit_atomic_write helds i_mmap_sem
lock to avoid this issue.
Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
v2:
- use i_mmap_sem to avoid mkwrite racing with below flows:
* f2fs_ioc_start_atomic_write
* f2fs_drop_inmem_pages
* f2fs_commit_inmem_pages
fs/f2fs/file.c | 3 +++
fs/f2fs/segment.c | 7 +++++++
2 files changed, 10 insertions(+)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 4e6d4b9120a8..a48ec650d691 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2050,6 +2050,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
goto out;
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+ down_write(&F2FS_I(inode)->i_mmap_sem);
/*
* Should wait end_io to count F2FS_WB_CP_DATA correctly by
@@ -2060,6 +2061,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
inode->i_ino, get_dirty_pages(inode));
ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
if (ret) {
+ up_write(&F2FS_I(inode)->i_mmap_sem);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
goto out;
}
@@ -2073,6 +2075,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
/* add inode in inmem_list first and set atomic_file */
set_inode_flag(inode, FI_ATOMIC_FILE);
clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
+ up_write(&F2FS_I(inode)->i_mmap_sem);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index d8570b0359f5..dab870d9faf6 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -327,6 +327,8 @@ void f2fs_drop_inmem_pages(struct inode *inode)
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct f2fs_inode_info *fi = F2FS_I(inode);
+ down_write(&F2FS_I(inode)->i_mmap_sem);
+
while (!list_empty(&fi->inmem_pages)) {
mutex_lock(&fi->inmem_lock);
__revoke_inmem_pages(inode, &fi->inmem_pages,
@@ -344,6 +346,8 @@ void f2fs_drop_inmem_pages(struct inode *inode)
sbi->atomic_files--;
}
spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
+
+ up_write(&F2FS_I(inode)->i_mmap_sem);
}
void f2fs_drop_inmem_page(struct inode *inode, struct page *page)
@@ -467,6 +471,7 @@ int f2fs_commit_inmem_pages(struct inode *inode)
f2fs_balance_fs(sbi, true);
down_write(&fi->i_gc_rwsem[WRITE]);
+ down_write(&F2FS_I(inode)->i_mmap_sem);
f2fs_lock_op(sbi);
set_inode_flag(inode, FI_ATOMIC_COMMIT);
@@ -478,6 +483,8 @@ int f2fs_commit_inmem_pages(struct inode *inode)
clear_inode_flag(inode, FI_ATOMIC_COMMIT);
f2fs_unlock_op(sbi);
+
+ up_write(&F2FS_I(inode)->i_mmap_sem);
up_write(&fi->i_gc_rwsem[WRITE]);
return err;
--
2.29.2
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