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Subject[PATCH 4.18 089/197] f2fs: fix avoid race between truncate and background GC
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chao Yu <yuchao0@huawei.com>

[ Upstream commit a33c150237a20d97a174243bc658c86502f9d370 ]

Thread A Background GC
- f2fs_setattr isize to 0
- truncate_setsize
- gc_data_segment
- f2fs_get_read_data_page page #0
- set_page_dirty
- set_cold_data
- f2fs_truncate

- f2fs_setattr isize to 4k
- read 4k <--- hit data in cached page #0

Above race condition can cause read out invalid data in a truncated
page, fix it by i_gc_rwsem[WRITE] lock.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/f2fs/data.c | 4 ++++
fs/f2fs/file.c | 37 +++++++++++++++++++++++--------------
2 files changed, 27 insertions(+), 14 deletions(-)

--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2149,8 +2149,12 @@ static void f2fs_write_failed(struct add

if (to > i_size) {
down_write(&F2FS_I(inode)->i_mmap_sem);
+ down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+
truncate_pagecache(inode, i_size);
f2fs_truncate_blocks(inode, i_size, true);
+
+ up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
up_write(&F2FS_I(inode)->i_mmap_sem);
}
}
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -782,22 +782,26 @@ int f2fs_setattr(struct dentry *dentry,
}

if (attr->ia_valid & ATTR_SIZE) {
- if (attr->ia_size <= i_size_read(inode)) {
- down_write(&F2FS_I(inode)->i_mmap_sem);
- truncate_setsize(inode, attr->ia_size);
+ bool to_smaller = (attr->ia_size <= i_size_read(inode));
+
+ down_write(&F2FS_I(inode)->i_mmap_sem);
+ down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+
+ truncate_setsize(inode, attr->ia_size);
+
+ if (to_smaller)
err = f2fs_truncate(inode);
- up_write(&F2FS_I(inode)->i_mmap_sem);
- if (err)
- return err;
- } else {
- /*
- * do not trim all blocks after i_size if target size is
- * larger than i_size.
- */
- down_write(&F2FS_I(inode)->i_mmap_sem);
- truncate_setsize(inode, attr->ia_size);
- up_write(&F2FS_I(inode)->i_mmap_sem);
+ /*
+ * do not trim all blocks after i_size if target size is
+ * larger than i_size.
+ */
+ up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+ up_write(&F2FS_I(inode)->i_mmap_sem);
+
+ if (err)
+ return err;

+ if (!to_smaller) {
/* should convert inline inode here */
if (!f2fs_may_inline_data(inode)) {
err = f2fs_convert_inline_inode(inode);
@@ -944,13 +948,18 @@ static int punch_hole(struct inode *inod

blk_start = (loff_t)pg_start << PAGE_SHIFT;
blk_end = (loff_t)pg_end << PAGE_SHIFT;
+
down_write(&F2FS_I(inode)->i_mmap_sem);
+ down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+
truncate_inode_pages_range(mapping, blk_start,
blk_end - 1);

f2fs_lock_op(sbi);
ret = f2fs_truncate_hole(inode, pg_start, pg_end);
f2fs_unlock_op(sbi);
+
+ up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
up_write(&F2FS_I(inode)->i_mmap_sem);
}
}

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