Messages in this thread Patch in this message | | | Subject | retry:[PATCH] fix error: a bin file can truncate itself while running on overlayfs | From | Zhang AiHua <> | Date | Mon, 27 Jun 2016 09:06:54 +0800 |
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-------- 转发的消息 -------- 主题: [PATCH] fix error: a bin file can truncate itself while running on overlayfs 日期: Wed, 22 Jun 2016 18:13:08 +0800 发件人: zhangaihua1@huawei.com 收件人: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-unionfs@vger.kernel.org 抄送: Aihua Zhang <zhangaihua1@huawei.com>
From: Aihua Zhang <zhangaihua1@huawei.com>
I wrote a testcase to truncate a bin file while it is running on overlayfs.
the mount: /dev/mapper/fedora-home on /home type ext4 (rw,relatime,data=ordered) overlay on /tmp type overlay (rw,relatime,lowerdir=/home/zah/lower, upperdir=/home/zah/upper,workdir=/home/zah/workdir)
the code cpp: int main(int argc, char *argv[]) { int status; pthread_t thread; int err; char *ptr;
ptr = basename(argv[0]); printf("%s\n",ptr); errno = 0;
status = truncate(ptr, 4096); printf("status:%d\n",status); printf("errno:%d\n",errno); printf("ETXTBSY:%d\n",ETXTBSY);
if ((-1 == status) && (ETXTBSY == errno)) { printf("PASS\n"); return 0; }
err = errno; printf("err = %d\n", err); printf("FAIL\n"); return 1; }
I running the test on overlayfs, the result as below: Bus error (core dumped)
and running the test on ext4, the result as below: status:-1 errno:26 ETXTBSY:26 PASS
I add some log, and I find the inode is not correct on overlayfs, and the inode->i_writecount is not correct also called by vfs_truncate-> get_write_access(), the log as below:
Jun 22 09:50:38 kernel: [131.872920] deny_write_access: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873109] deny_write_access: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873110] __vma_link_file: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873112] allow_write_access: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873114] deny_write_access: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873115] __vma_link_file: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873116] allow_write_access: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873162] allow_write_access: inode ino 64104618 Jun 22 09:50:38 kernel: [131.873947] __vma_link_file: inode ino 64104618 Jun 22 09:50:38 kernel: [131.874039] vfs_truncate: inode ino:24061
before vfs_truncate, the inode is point to upper filesystem(ext4), and in vfs_truncate the inode is point to overlayfs.
So, I fix it by geting the real inode via ovl_d_select_inode.
Signed-off-by: Aihua Zhang <zhangaihua1@huawei.com> --- fs/open.c | 10 ++++++++-- 1 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/open.c b/fs/open.c index 93ae3cd..43b17d1 100644 --- a/fs/open.c +++ b/fs/open.c @@ -67,10 +67,16 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
long vfs_truncate(const struct path *path, loff_t length) { + struct dentry *dentry = path->dentry; struct inode *inode; long error;
- inode = path->dentry->d_inode; + if (dentry->d_flags & DCACHE_OP_SELECT_INODE) { + inode = dentry->d_op->d_select_inode(dentry, O_TRUNC); + if (IS_ERR(inode)) + return PTR_ERR(inode); + } else + inode = dentry->d_inode;
/* For directories it's -EISDIR, for other non-regulars - -EINVAL */ if (S_ISDIR(inode->i_mode)) @@ -106,7 +112,7 @@ long vfs_truncate(const struct path *path, loff_t length) if (!error) error = security_path_truncate(path); if (!error) - error = do_truncate(path->dentry, length, 0, NULL); + error = do_truncate(dentry, length, 0, NULL);
put_write_and_out: put_write_access(inode); -- 1.7.1
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