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overlayfs: Make f_path always point to the overlay and f_inode to the underlay
Make file->f_path always point to the overlay dentry so that the path in /proc/pid/fd is correct and to ensure that label-based LSMs have access to the overlay as well as the underlay (path-based LSMs probably don't need it). Using my union testsuite to set things up, before the patch I see: [root@andromeda union-testsuite]# bash 5</mnt/a/foo107 [root@andromeda union-testsuite]# ls -l /proc/$$/fd/ ... lr-x------. 1 root root 64 Jun 5 14:38 5 -> /a/foo107 [root@andromeda union-testsuite]# stat /mnt/a/foo107 ... Device: 23h/35d Inode: 13381 Links: 1 ... [root@andromeda union-testsuite]# stat -L /proc/$$/fd/5 ... Device: 23h/35d Inode: 13381 Links: 1 ... After the patch: [root@andromeda union-testsuite]# bash 5</mnt/a/foo107 [root@andromeda union-testsuite]# ls -l /proc/$$/fd/ ... lr-x------. 1 root root 64 Jun 5 14:22 5 -> /mnt/a/foo107 [root@andromeda union-testsuite]# stat /mnt/a/foo107 ... Device: 23h/35d Inode: 40346 Links: 1 ... [root@andromeda union-testsuite]# stat -L /proc/$$/fd/5 ... Device: 23h/35d Inode: 40346 Links: 1 ... Note the change in where /proc/$$/fd/5 points to in the ls command. It was pointing to /a/foo107 (which doesn't exist) and now points to /mnt/a/foo107 (which is correct). The inode accessed, however, is the lower layer. The union layer is on device 25h/37d and the upper layer on 24h/36d. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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f25801ee46
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4bacc9c923
@ -1673,7 +1673,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
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DCACHE_OP_COMPARE |
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DCACHE_OP_REVALIDATE |
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DCACHE_OP_WEAK_REVALIDATE |
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DCACHE_OP_DELETE ));
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DCACHE_OP_DELETE |
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DCACHE_OP_SELECT_INODE));
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dentry->d_op = op;
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if (!op)
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return;
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@ -1689,6 +1690,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
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dentry->d_flags |= DCACHE_OP_DELETE;
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if (op->d_prune)
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dentry->d_flags |= DCACHE_OP_PRUNE;
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if (op->d_select_inode)
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dentry->d_flags |= DCACHE_OP_SELECT_INODE;
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}
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EXPORT_SYMBOL(d_set_d_op);
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@ -107,6 +107,7 @@ extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
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extern long do_handle_open(int mountdirfd,
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struct file_handle __user *ufh, int open_flag);
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extern int open_check_o_direct(struct file *f);
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extern int vfs_open(const struct path *, struct file *, const struct cred *);
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/*
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* inode.c
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49
fs/open.c
49
fs/open.c
@ -678,18 +678,18 @@ int open_check_o_direct(struct file *f)
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}
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static int do_dentry_open(struct file *f,
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struct inode *inode,
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int (*open)(struct inode *, struct file *),
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const struct cred *cred)
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{
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static const struct file_operations empty_fops = {};
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struct inode *inode;
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int error;
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f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
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FMODE_PREAD | FMODE_PWRITE;
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path_get(&f->f_path);
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inode = f->f_inode = f->f_path.dentry->d_inode;
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f->f_inode = inode;
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f->f_mapping = inode->i_mapping;
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if (unlikely(f->f_flags & O_PATH)) {
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@ -793,7 +793,8 @@ int finish_open(struct file *file, struct dentry *dentry,
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BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
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file->f_path.dentry = dentry;
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error = do_dentry_open(file, open, current_cred());
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error = do_dentry_open(file, d_backing_inode(dentry), open,
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current_cred());
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if (!error)
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*opened |= FILE_OPENED;
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@ -822,6 +823,28 @@ int finish_no_open(struct file *file, struct dentry *dentry)
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}
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EXPORT_SYMBOL(finish_no_open);
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/**
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* vfs_open - open the file at the given path
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* @path: path to open
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* @file: newly allocated file with f_flag initialized
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* @cred: credentials to use
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*/
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int vfs_open(const struct path *path, struct file *file,
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const struct cred *cred)
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{
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struct dentry *dentry = path->dentry;
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struct inode *inode = dentry->d_inode;
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file->f_path = *path;
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if (dentry->d_flags & DCACHE_OP_SELECT_INODE) {
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inode = dentry->d_op->d_select_inode(dentry, file->f_flags);
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if (IS_ERR(inode))
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return PTR_ERR(inode);
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}
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return do_dentry_open(file, inode, NULL, cred);
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}
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struct file *dentry_open(const struct path *path, int flags,
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const struct cred *cred)
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{
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@ -853,26 +876,6 @@ struct file *dentry_open(const struct path *path, int flags,
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}
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EXPORT_SYMBOL(dentry_open);
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/**
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* vfs_open - open the file at the given path
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* @path: path to open
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* @filp: newly allocated file with f_flag initialized
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* @cred: credentials to use
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*/
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int vfs_open(const struct path *path, struct file *filp,
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const struct cred *cred)
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{
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struct inode *inode = path->dentry->d_inode;
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if (inode->i_op->dentry_open)
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return inode->i_op->dentry_open(path->dentry, filp, cred);
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else {
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filp->f_path = *path;
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return do_dentry_open(filp, NULL, cred);
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}
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}
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EXPORT_SYMBOL(vfs_open);
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static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
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{
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int lookup_flags = 0;
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@ -337,31 +337,30 @@ static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
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return true;
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}
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static int ovl_dentry_open(struct dentry *dentry, struct file *file,
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const struct cred *cred)
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struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
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{
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int err;
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struct path realpath;
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enum ovl_path_type type;
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type = ovl_path_real(dentry, &realpath);
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if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
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if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
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err = ovl_want_write(dentry);
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if (err)
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return err;
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return ERR_PTR(err);
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if (file->f_flags & O_TRUNC)
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if (file_flags & O_TRUNC)
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err = ovl_copy_up_last(dentry, NULL, true);
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else
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err = ovl_copy_up(dentry);
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ovl_drop_write(dentry);
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if (err)
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return err;
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return ERR_PTR(err);
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ovl_path_upper(dentry, &realpath);
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}
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return vfs_open(&realpath, file, cred);
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return d_backing_inode(realpath.dentry);
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}
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static const struct inode_operations ovl_file_inode_operations = {
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@ -372,7 +371,6 @@ static const struct inode_operations ovl_file_inode_operations = {
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.getxattr = ovl_getxattr,
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.listxattr = ovl_listxattr,
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.removexattr = ovl_removexattr,
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.dentry_open = ovl_dentry_open,
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};
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static const struct inode_operations ovl_symlink_inode_operations = {
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@ -173,6 +173,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
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void *value, size_t size);
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ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
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int ovl_removexattr(struct dentry *dentry, const char *name);
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struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags);
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struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
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struct ovl_entry *oe);
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@ -275,6 +275,7 @@ static void ovl_dentry_release(struct dentry *dentry)
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static const struct dentry_operations ovl_dentry_operations = {
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.d_release = ovl_dentry_release,
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.d_select_inode = ovl_d_select_inode,
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};
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static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
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@ -160,6 +160,7 @@ struct dentry_operations {
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char *(*d_dname)(struct dentry *, char *, int);
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struct vfsmount *(*d_automount)(struct path *);
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int (*d_manage)(struct dentry *, bool);
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struct inode *(*d_select_inode)(struct dentry *, unsigned);
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} ____cacheline_aligned;
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/*
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@ -225,6 +226,7 @@ struct dentry_operations {
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#define DCACHE_MAY_FREE 0x00800000
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#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
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#define DCACHE_OP_SELECT_INODE 0x02000000 /* Unioned entry: dcache op selects inode */
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extern seqlock_t rename_lock;
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@ -1641,7 +1641,6 @@ struct inode_operations {
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int (*set_acl)(struct inode *, struct posix_acl *, int);
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/* WARNING: probably going away soon, do not use! */
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int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
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} ____cacheline_aligned;
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ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
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@ -2194,7 +2193,6 @@ extern struct file *file_open_name(struct filename *, int, umode_t);
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extern struct file *filp_open(const char *, int, umode_t);
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extern struct file *file_open_root(struct dentry *, struct vfsmount *,
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const char *, int);
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extern int vfs_open(const struct path *, struct file *, const struct cred *);
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extern struct file * dentry_open(const struct path *, int, const struct cred *);
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extern int filp_close(struct file *, fl_owner_t id);
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