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: d1d04ef857
("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>
This commit is contained in:
parent
3428030da0
commit
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@ -144,11 +144,47 @@ static int ovl_release(struct inode *inode, struct file *file)
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static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
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{
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struct inode *realinode = ovl_inode_real(file_inode(file));
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struct inode *inode = file_inode(file);
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struct fd real;
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const struct cred *old_cred;
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ssize_t ret;
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return generic_file_llseek_size(file, offset, whence,
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realinode->i_sb->s_maxbytes,
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i_size_read(realinode));
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/*
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* The two special cases below do not need to involve real fs,
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* so we can optimizing concurrent callers.
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*/
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if (offset == 0) {
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if (whence == SEEK_CUR)
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return file->f_pos;
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if (whence == SEEK_SET)
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return vfs_setpos(file, 0, 0);
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}
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ret = ovl_real_fdget(file, &real);
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if (ret)
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return ret;
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/*
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* Overlay file f_pos is the master copy that is preserved
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* through copy up and modified on read/write, but only real
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* fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
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* limitations that are more strict than ->s_maxbytes for specific
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* files, so we use the real file to perform seeks.
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*/
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inode_lock(inode);
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real.file->f_pos = file->f_pos;
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old_cred = ovl_override_creds(inode->i_sb);
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ret = vfs_llseek(real.file, offset, whence);
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revert_creds(old_cred);
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file->f_pos = real.file->f_pos;
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inode_unlock(inode);
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fdput(real);
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return ret;
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}
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static void ovl_file_accessed(struct file *file)
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