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| author | Amir Goldstein <amir73il@gmail.com> | 2019-02-27 14:32:11 +0300 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2019-05-06 14:54:51 +0300 |
| commit | 9e46b840c7053b5f7a245e98cd239b60d189a96c (patch) | |
| tree | 802b84ae86ddae6b08875cc7d219995e618214ff /fs/overlayfs | |
| parent | 3428030da004a1128cbdcf93dc03e16f184d845b (diff) | |
| download | linux-9e46b840c7053b5f7a245e98cd239b60d189a96c.tar.xz | |
ovl: support stacked SEEK_HOLE/SEEK_DATA
Overlay file f_pos is the master copy that is preserved
through copy up and modified on read/write, but only real
fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
limitations that are more strict than ->s_maxbytes for specific
files, so we use the real file to perform seeks.
We do not call real fs for SEEK_CUR:0 query and for SEEK_SET:0
requests.
Fixes: d1d04ef8572b ("ovl: stack file ops")
Reported-by: Eddie Horng <eddiehorng.tw@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/file.c | 44 |
1 files changed, 40 insertions, 4 deletions
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 50e4407398d8..ddfd93f13cc5 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -144,11 +144,47 @@ static int ovl_release(struct inode *inode, struct file *file) static loff_t ovl_llseek(struct file *file, loff_t offset, int whence) { - struct inode *realinode = ovl_inode_real(file_inode(file)); + struct inode *inode = file_inode(file); + struct fd real; + const struct cred *old_cred; + ssize_t ret; + + /* + * The two special cases below do not need to involve real fs, + * so we can optimizing concurrent callers. + */ + if (offset == 0) { + if (whence == SEEK_CUR) + return file->f_pos; + + if (whence == SEEK_SET) + return vfs_setpos(file, 0, 0); + } + + ret = ovl_real_fdget(file, &real); + if (ret) + return ret; - return generic_file_llseek_size(file, offset, whence, - realinode->i_sb->s_maxbytes, - i_size_read(realinode)); + /* + * Overlay file f_pos is the master copy that is preserved + * through copy up and modified on read/write, but only real + * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose + * limitations that are more strict than ->s_maxbytes for specific + * files, so we use the real file to perform seeks. + */ + inode_lock(inode); + real.file->f_pos = file->f_pos; + + old_cred = ovl_override_creds(inode->i_sb); + ret = vfs_llseek(real.file, offset, whence); + revert_creds(old_cred); + + file->f_pos = real.file->f_pos; + inode_unlock(inode); + + fdput(real); + + return ret; } static void ovl_file_accessed(struct file *file) |