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Subject[PATCH -V7 4/9] vfs: Add open by file handle support
Date
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/namei.c | 24 ---------
fs/open.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/namei.h | 24 +++++++++
3 files changed, 160 insertions(+), 24 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index a7dce91..a18711e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1521,30 +1521,6 @@ out_unlock:
return may_open(&nd->path, 0, open_flag & ~O_TRUNC);
}

-/*
- * Note that while the flag value (low two bits) for sys_open means:
- * 00 - read-only
- * 01 - write-only
- * 10 - read-write
- * 11 - special
- * it is changed into
- * 00 - no permissions needed
- * 01 - read-permission
- * 10 - write-permission
- * 11 - read-write
- * for the internal routines (ie open_namei()/follow_link() etc)
- * This is more logical, and also allows the 00 "no perm needed"
- * to be used for symlinks (where the permissions are checked
- * later).
- *
-*/
-static inline int open_to_namei_flags(int flag)
-{
- if ((flag+1) & O_ACCMODE)
- flag++;
- return flag;
-}
-
static int open_will_truncate(int flag, struct inode *inode)
{
/*
diff --git a/fs/open.c b/fs/open.c
index 9a34b81..348a1b9 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1315,3 +1315,139 @@ err_out:
asmlinkage_protect(4, ret, dfd, name, handle, flag);
return ret;
}
+
+static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
+{
+ return 1;
+}
+
+static struct dentry *handle_to_dentry(struct vfsmount *mnt,
+ struct file_handle *handle)
+{
+ int handle_size;
+ struct dentry *dentry;
+
+ /* change the handle size to multiple of sizeof(u32) */
+ handle_size = handle->handle_size >> 2;
+ dentry = exportfs_decode_fh(mnt, (struct fid *)handle->f_handle,
+ handle_size, handle->handle_type,
+ vfs_dentry_acceptable, NULL);
+ return dentry;
+}
+
+static long do_sys_open_by_handle(struct file_handle __user *ufh, int flags)
+{
+ int fd;
+ int retval = 0;
+ int d_flags = flags;
+ struct file *filp;
+ struct vfsmount *mnt;
+ struct inode *inode;
+ struct dentry *dentry;
+ struct file_handle f_handle;
+ struct file_handle *handle = NULL;
+
+ if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
+ retval = -EFAULT;
+ goto out_err;
+ }
+ if ((f_handle.handle_size > MAX_HANDLE_SZ) ||
+ (f_handle.handle_size <= 0)) {
+ retval = -EINVAL;
+ goto out_err;
+ }
+ if (!capable(CAP_DAC_OVERRIDE)) {
+ retval = -EPERM;
+ goto out_err;
+ }
+ /*
+ * Find the vfsmount for this uuid in the
+ * current namespace
+ */
+ mnt = fs_get_vfsmount(current, &f_handle.fsid);
+ if (!mnt) {
+ retval = -ESTALE;
+ goto out_err;
+ }
+
+ handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size,
+ GFP_KERNEL);
+ if (!handle) {
+ retval = -ENOMEM;
+ goto out_mnt;
+ }
+ /* copy the full handle */
+ if (copy_from_user(handle, ufh,
+ sizeof(struct file_handle) +
+ f_handle.handle_size)) {
+ retval = -EFAULT;
+ goto out_mnt;
+ }
+ dentry = handle_to_dentry(mnt, handle);
+ if (IS_ERR(dentry)) {
+ retval = PTR_ERR(dentry);
+ goto out_mnt;
+ }
+ inode = dentry->d_inode;
+ flags = open_to_namei_flags(flags);
+ /* O_TRUNC implies we need access checks for write permissions */
+ if (flags & O_TRUNC)
+ flags |= MAY_WRITE;
+
+ if ((!(flags & O_APPEND) || (flags & O_TRUNC)) &&
+ (flags & FMODE_WRITE) && IS_APPEND(inode)) {
+ retval = -EPERM;
+ goto out_dentry;
+ }
+ if ((flags & FMODE_WRITE) && IS_IMMUTABLE(inode)) {
+ retval = -EACCES;
+ goto out_dentry;
+ }
+ /* Can't write directories. */
+ if (S_ISDIR(inode->i_mode) && (flags & FMODE_WRITE)) {
+ retval = -EISDIR;
+ goto out_dentry;
+ }
+ fd = get_unused_fd_flags(d_flags);
+ if (fd < 0) {
+ retval = fd;
+ goto out_dentry;
+ }
+ filp = dentry_open(dget(dentry), mntget(mnt),
+ d_flags, current_cred());
+ if (IS_ERR(filp)) {
+ put_unused_fd(fd);
+ retval = PTR_ERR(filp);
+ goto out_dentry;
+ }
+ if (inode->i_mode & S_IFREG) {
+ filp->f_flags |= O_NOATIME;
+ filp->f_mode |= FMODE_NOCMTIME;
+ }
+ fsnotify_open(filp->f_path.dentry);
+ fd_install(fd, filp);
+ retval = fd;
+
+out_dentry:
+ dput(dentry);
+out_mnt:
+ kfree(handle);
+ mntput(mnt);
+out_err:
+ return retval;
+}
+
+SYSCALL_DEFINE2(open_by_handle, struct file_handle __user *, handle,
+ int, flags)
+{
+ long ret;
+
+ if (force_o_largefile())
+ flags |= O_LARGEFILE;
+
+ ret = do_sys_open_by_handle(handle, flags);
+
+ /* avoid REGPARM breakage on x86: */
+ asmlinkage_protect(2, ret, handle, flags);
+ return ret;
+}
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 05b441d..a853aa0 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -4,6 +4,7 @@
#include <linux/dcache.h>
#include <linux/linkage.h>
#include <linux/path.h>
+#include <asm-generic/fcntl.h>

struct vfsmount;

@@ -96,4 +97,27 @@ static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
((char *) name)[min(len, maxlen)] = '\0';
}

+/*
+ * Note that while the flag value (low two bits) for sys_open means:
+ * 00 - read-only
+ * 01 - write-only
+ * 10 - read-write
+ * 11 - special
+ * it is changed into
+ * 00 - no permissions needed
+ * 01 - read-permission
+ * 10 - write-permission
+ * 11 - read-write
+ * for the internal routines (ie open_namei()/follow_link() etc)
+ * This is more logical, and also allows the 00 "no perm needed"
+ * to be used for symlinks (where the permissions are checked
+ * later).
+ *
+*/
+static inline int open_to_namei_flags(int flag)
+{
+ if ((flag+1) & O_ACCMODE)
+ flag++;
+ return flag;
+}
#endif /* _LINUX_NAMEI_H */
--
1.7.1.78.g212f0


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