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Date: Thu, 4 May 2017 08:16:59 +0800
From: sunqiuyang <sunqiuyang@...wei.com>
To: <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
CC: <miaoxie@...wei.com>, <zhaohongjiang@...wei.com>,
<fangwei1@...wei.com>, <wangyijing@...wei.com>,
<yi.zhang@...wei.com>, <guzheng1@...wei.com>,
<dingxiang@...wei.com>, <houtao1@...wei.com>,
<yanaijie@...wei.com>, <wenyuzhong1@...wei.com>,
<wangxiaojun11@...wei.com>, <sunqiuyang@...wei.com>
Subject: [PATCH 1/3] f2fs:dax: fix races between page faults and fallocate
Currently in F2FS, page faults and fallocate operations, like punch_hole
and collapse/insert/zero_range, are completely unsynchronized. This can
result in page fault faulting in a page into a range that we are changing
after truncating pagecache, and thus we can end up with a page mapped to
disk blocks that will be shortly freed. Filesystem corruption will shortly
follow.
This patch fixes the problem by creating new rw semaphore i_mmap_sem in
f2fs_inode_info and grab it for functions removing blocks from extent tree
and for read over page faults. The mechanism is similar to that in ext4.
Signed-off-by: Qiuyang Sun <sunqiuyang@...wei.com>
---
fs/f2fs/f2fs.h | 1 +
fs/f2fs/file.c | 30 +++++++++++++++++++++---------
fs/f2fs/super.c | 1 +
3 files changed, 23 insertions(+), 9 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 0a6e115..f7957ca 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -474,6 +474,7 @@ struct f2fs_inode_info {
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 */
+ struct rw_semaphore i_mmap_sem;
};
static inline void get_extent_info(struct extent_info *ext,
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 5f73178..165acbf 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -813,22 +813,23 @@ static int punch_hole(struct inode *inode, loff_t offset, loff_t len)
off_start = offset & (PAGE_SIZE - 1);
off_end = (offset + len) & (PAGE_SIZE - 1);
+ down_write(&F2FS_I(inode)->i_mmap_sem);
if (pg_start == pg_end) {
ret = fill_zero(inode, pg_start, off_start,
off_end - off_start);
if (ret)
- return ret;
+ goto out;
} else {
if (off_start) {
ret = fill_zero(inode, pg_start++, off_start,
PAGE_SIZE - off_start);
if (ret)
- return ret;
+ goto out;
}
if (off_end) {
ret = fill_zero(inode, pg_end, 0, off_end);
if (ret)
- return ret;
+ goto out;
}
if (pg_start < pg_end) {
@@ -849,6 +850,8 @@ static int punch_hole(struct inode *inode, loff_t offset, loff_t len)
}
}
+out:
+ up_write(&F2FS_I(inode)->i_mmap_sem);
return ret;
}
@@ -1084,16 +1087,17 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
pg_start = offset >> PAGE_SHIFT;
pg_end = (offset + len) >> PAGE_SHIFT;
+ down_write(&F2FS_I(inode)->i_mmap_sem);
/* write out all dirty pages from offset */
ret = filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
if (ret)
- return ret;
+ goto out;
truncate_pagecache(inode, offset);
ret = f2fs_do_collapse(inode, pg_start, pg_end);
if (ret)
- return ret;
+ goto out;
/* write out all moved pages, if possible */
filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
@@ -1106,6 +1110,8 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
if (!ret)
f2fs_i_size_write(inode, new_size);
+out:
+ up_write(&F2FS_I(inode)->i_mmap_sem);
return ret;
}
@@ -1182,11 +1188,12 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
off_start = offset & (PAGE_SIZE - 1);
off_end = (offset + len) & (PAGE_SIZE - 1);
+ down_write(&F2FS_I(inode)->i_mmap_sem);
if (pg_start == pg_end) {
ret = fill_zero(inode, pg_start, off_start,
off_end - off_start);
if (ret)
- return ret;
+ goto unlock;
if (offset + len > new_size)
new_size = offset + len;
@@ -1196,7 +1203,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
ret = fill_zero(inode, pg_start++, off_start,
PAGE_SIZE - off_start);
if (ret)
- return ret;
+ goto unlock;
new_size = max_t(loff_t, new_size,
(loff_t)pg_start << PAGE_SHIFT);
@@ -1245,6 +1252,8 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
out:
if (!(mode & FALLOC_FL_KEEP_SIZE) && i_size_read(inode) < new_size)
f2fs_i_size_write(inode, new_size);
+unlock:
+ up_write(&F2FS_I(inode)->i_mmap_sem);
return ret;
}
@@ -1271,16 +1280,17 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
if (ret)
return ret;
+ down_write(&F2FS_I(inode)->i_mmap_sem);
f2fs_balance_fs(sbi, true);
ret = truncate_blocks(inode, i_size_read(inode), true);
if (ret)
- return ret;
+ goto out;
/* write out all dirty pages from offset */
ret = filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
if (ret)
- return ret;
+ goto out;
truncate_pagecache(inode, offset);
@@ -1309,6 +1319,8 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
if (!ret)
f2fs_i_size_write(inode, new_size);
+out:
+ up_write(&F2FS_I(inode)->i_mmap_sem);
return ret;
}
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 96fe8ed..30855cf 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -616,6 +616,7 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
mutex_init(&fi->inmem_lock);
init_rwsem(&fi->dio_rwsem[READ]);
init_rwsem(&fi->dio_rwsem[WRITE]);
+ init_rwsem(&fi->i_mmap_sem);
/* Will be used by directory only */
fi->i_dir_level = F2FS_SB(sb)->dir_level;
--
1.8.3.1
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