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![Miklos Szeredi](/assets/img/avatar_default.png)
Combine inode creation with opening a file. There are six separate objects that are being set up: the backing inode, dentry and file, and the overlay inode, dentry and file. Cleanup in case of an error is a bit of a challenge and is difficult to test, so careful review is needed. All tmpfile testcases except generic/509 now run/pass, and no regressions are observed with full xfstests. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
358 lines
8.3 KiB
C
358 lines
8.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Common helpers for stackable filesystems and backing files.
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*
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* Forked from fs/overlayfs/file.c.
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*
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* Copyright (C) 2017 Red Hat, Inc.
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* Copyright (C) 2023 CTERA Networks.
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*/
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#include <linux/fs.h>
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#include <linux/backing-file.h>
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#include <linux/splice.h>
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#include <linux/mm.h>
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#include "internal.h"
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/**
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* backing_file_open - open a backing file for kernel internal use
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* @user_path: path that the user reuqested to open
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* @flags: open flags
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* @real_path: path of the backing file
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* @cred: credentials for open
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*
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* Open a backing file for a stackable filesystem (e.g., overlayfs).
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* @user_path may be on the stackable filesystem and @real_path on the
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* underlying filesystem. In this case, we want to be able to return the
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* @user_path of the stackable filesystem. This is done by embedding the
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* returned file into a container structure that also stores the stacked
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* file's path, which can be retrieved using backing_file_user_path().
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*/
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struct file *backing_file_open(const struct path *user_path, int flags,
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const struct path *real_path,
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const struct cred *cred)
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{
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struct file *f;
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int error;
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f = alloc_empty_backing_file(flags, cred);
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if (IS_ERR(f))
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return f;
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path_get(user_path);
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*backing_file_user_path(f) = *user_path;
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error = vfs_open(real_path, f);
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if (error) {
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fput(f);
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f = ERR_PTR(error);
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}
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return f;
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}
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EXPORT_SYMBOL_GPL(backing_file_open);
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struct file *backing_tmpfile_open(const struct path *user_path, int flags,
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const struct path *real_parentpath,
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umode_t mode, const struct cred *cred)
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{
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struct mnt_idmap *real_idmap = mnt_idmap(real_parentpath->mnt);
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struct file *f;
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int error;
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f = alloc_empty_backing_file(flags, cred);
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if (IS_ERR(f))
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return f;
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path_get(user_path);
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*backing_file_user_path(f) = *user_path;
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error = vfs_tmpfile(real_idmap, real_parentpath, f, mode);
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if (error) {
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fput(f);
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f = ERR_PTR(error);
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}
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return f;
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}
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EXPORT_SYMBOL(backing_tmpfile_open);
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struct backing_aio {
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struct kiocb iocb;
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refcount_t ref;
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struct kiocb *orig_iocb;
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/* used for aio completion */
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void (*end_write)(struct file *);
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struct work_struct work;
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long res;
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};
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static struct kmem_cache *backing_aio_cachep;
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#define BACKING_IOCB_MASK \
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(IOCB_NOWAIT | IOCB_HIPRI | IOCB_DSYNC | IOCB_SYNC | IOCB_APPEND)
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static rwf_t iocb_to_rw_flags(int flags)
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{
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return (__force rwf_t)(flags & BACKING_IOCB_MASK);
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}
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static void backing_aio_put(struct backing_aio *aio)
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{
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if (refcount_dec_and_test(&aio->ref)) {
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fput(aio->iocb.ki_filp);
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kmem_cache_free(backing_aio_cachep, aio);
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}
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}
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static void backing_aio_cleanup(struct backing_aio *aio, long res)
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{
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struct kiocb *iocb = &aio->iocb;
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struct kiocb *orig_iocb = aio->orig_iocb;
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if (aio->end_write)
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aio->end_write(orig_iocb->ki_filp);
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orig_iocb->ki_pos = iocb->ki_pos;
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backing_aio_put(aio);
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}
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static void backing_aio_rw_complete(struct kiocb *iocb, long res)
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{
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struct backing_aio *aio = container_of(iocb, struct backing_aio, iocb);
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struct kiocb *orig_iocb = aio->orig_iocb;
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if (iocb->ki_flags & IOCB_WRITE)
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kiocb_end_write(iocb);
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backing_aio_cleanup(aio, res);
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orig_iocb->ki_complete(orig_iocb, res);
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}
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static void backing_aio_complete_work(struct work_struct *work)
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{
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struct backing_aio *aio = container_of(work, struct backing_aio, work);
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backing_aio_rw_complete(&aio->iocb, aio->res);
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}
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static void backing_aio_queue_completion(struct kiocb *iocb, long res)
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{
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struct backing_aio *aio = container_of(iocb, struct backing_aio, iocb);
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/*
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* Punt to a work queue to serialize updates of mtime/size.
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*/
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aio->res = res;
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INIT_WORK(&aio->work, backing_aio_complete_work);
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queue_work(file_inode(aio->orig_iocb->ki_filp)->i_sb->s_dio_done_wq,
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&aio->work);
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}
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static int backing_aio_init_wq(struct kiocb *iocb)
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{
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struct super_block *sb = file_inode(iocb->ki_filp)->i_sb;
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if (sb->s_dio_done_wq)
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return 0;
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return sb_init_dio_done_wq(sb);
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}
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ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
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struct kiocb *iocb, int flags,
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struct backing_file_ctx *ctx)
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{
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struct backing_aio *aio = NULL;
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const struct cred *old_cred;
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ssize_t ret;
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if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
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return -EIO;
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if (!iov_iter_count(iter))
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return 0;
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if (iocb->ki_flags & IOCB_DIRECT &&
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!(file->f_mode & FMODE_CAN_ODIRECT))
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return -EINVAL;
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old_cred = override_creds(ctx->cred);
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if (is_sync_kiocb(iocb)) {
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rwf_t rwf = iocb_to_rw_flags(flags);
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ret = vfs_iter_read(file, iter, &iocb->ki_pos, rwf);
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} else {
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ret = -ENOMEM;
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aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);
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if (!aio)
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goto out;
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aio->orig_iocb = iocb;
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kiocb_clone(&aio->iocb, iocb, get_file(file));
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aio->iocb.ki_complete = backing_aio_rw_complete;
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refcount_set(&aio->ref, 2);
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ret = vfs_iocb_iter_read(file, &aio->iocb, iter);
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backing_aio_put(aio);
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if (ret != -EIOCBQUEUED)
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backing_aio_cleanup(aio, ret);
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}
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out:
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revert_creds(old_cred);
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if (ctx->accessed)
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ctx->accessed(ctx->user_file);
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return ret;
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}
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EXPORT_SYMBOL_GPL(backing_file_read_iter);
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ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,
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struct kiocb *iocb, int flags,
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struct backing_file_ctx *ctx)
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{
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const struct cred *old_cred;
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ssize_t ret;
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if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
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return -EIO;
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if (!iov_iter_count(iter))
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return 0;
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ret = file_remove_privs(ctx->user_file);
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if (ret)
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return ret;
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if (iocb->ki_flags & IOCB_DIRECT &&
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!(file->f_mode & FMODE_CAN_ODIRECT))
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return -EINVAL;
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/*
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* Stacked filesystems don't support deferred completions, don't copy
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* this property in case it is set by the issuer.
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*/
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flags &= ~IOCB_DIO_CALLER_COMP;
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old_cred = override_creds(ctx->cred);
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if (is_sync_kiocb(iocb)) {
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rwf_t rwf = iocb_to_rw_flags(flags);
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ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf);
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if (ctx->end_write)
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ctx->end_write(ctx->user_file);
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} else {
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struct backing_aio *aio;
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ret = backing_aio_init_wq(iocb);
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if (ret)
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goto out;
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ret = -ENOMEM;
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aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);
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if (!aio)
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goto out;
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aio->orig_iocb = iocb;
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aio->end_write = ctx->end_write;
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kiocb_clone(&aio->iocb, iocb, get_file(file));
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aio->iocb.ki_flags = flags;
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aio->iocb.ki_complete = backing_aio_queue_completion;
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refcount_set(&aio->ref, 2);
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ret = vfs_iocb_iter_write(file, &aio->iocb, iter);
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backing_aio_put(aio);
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if (ret != -EIOCBQUEUED)
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backing_aio_cleanup(aio, ret);
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}
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out:
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revert_creds(old_cred);
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return ret;
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}
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EXPORT_SYMBOL_GPL(backing_file_write_iter);
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ssize_t backing_file_splice_read(struct file *in, loff_t *ppos,
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struct pipe_inode_info *pipe, size_t len,
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unsigned int flags,
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struct backing_file_ctx *ctx)
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{
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const struct cred *old_cred;
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ssize_t ret;
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if (WARN_ON_ONCE(!(in->f_mode & FMODE_BACKING)))
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return -EIO;
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old_cred = override_creds(ctx->cred);
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ret = vfs_splice_read(in, ppos, pipe, len, flags);
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revert_creds(old_cred);
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if (ctx->accessed)
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ctx->accessed(ctx->user_file);
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return ret;
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}
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EXPORT_SYMBOL_GPL(backing_file_splice_read);
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ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
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struct file *out, loff_t *ppos, size_t len,
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unsigned int flags,
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struct backing_file_ctx *ctx)
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{
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const struct cred *old_cred;
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ssize_t ret;
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if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING)))
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return -EIO;
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ret = file_remove_privs(ctx->user_file);
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if (ret)
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return ret;
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old_cred = override_creds(ctx->cred);
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file_start_write(out);
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ret = iter_file_splice_write(pipe, out, ppos, len, flags);
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file_end_write(out);
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revert_creds(old_cred);
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if (ctx->end_write)
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ctx->end_write(ctx->user_file);
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return ret;
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}
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EXPORT_SYMBOL_GPL(backing_file_splice_write);
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int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
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struct backing_file_ctx *ctx)
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{
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const struct cred *old_cred;
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int ret;
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if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)) ||
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WARN_ON_ONCE(ctx->user_file != vma->vm_file))
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return -EIO;
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if (!file->f_op->mmap)
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return -ENODEV;
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vma_set_file(vma, file);
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old_cred = override_creds(ctx->cred);
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ret = call_mmap(vma->vm_file, vma);
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revert_creds(old_cred);
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if (ctx->accessed)
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ctx->accessed(ctx->user_file);
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return ret;
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}
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EXPORT_SYMBOL_GPL(backing_file_mmap);
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static int __init backing_aio_init(void)
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{
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backing_aio_cachep = KMEM_CACHE(backing_aio, SLAB_HWCACHE_ALIGN);
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if (!backing_aio_cachep)
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return -ENOMEM;
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return 0;
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}
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fs_initcall(backing_aio_init);
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