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// SPDX-License-Identifier: GPL-2.0
/*
* FUSE passthrough to backing file.
*
* Copyright (c) 2023 CTERA Networks.
*/
#include "fuse_i.h"
#include <linux/file.h>
#include <linux/backing-file.h>
#include <linux/splice.h>
static void fuse_file_accessed(struct file *file)
{
struct inode *inode = file_inode(file);
fuse_invalidate_atime(inode);
}
static void fuse_passthrough_end_write(struct kiocb *iocb, ssize_t ret)
{
struct inode *inode = file_inode(iocb->ki_filp);
fuse_write_update_attr(inode, iocb->ki_pos, ret);
}
ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct fuse_file *ff = file->private_data;
struct file *backing_file = fuse_file_passthrough(ff);
size_t count = iov_iter_count(iter);
ssize_t ret;
struct backing_file_ctx ctx = {
.cred = ff->cred,
.accessed = fuse_file_accessed,
};
pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu\n", __func__,
backing_file, iocb->ki_pos, count);
if (!count)
return 0;
ret = backing_file_read_iter(backing_file, iter, iocb, iocb->ki_flags,
&ctx);
return ret;
}
ssize_t fuse_passthrough_write_iter(struct kiocb *iocb,
struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(file);
struct fuse_file *ff = file->private_data;
struct file *backing_file = fuse_file_passthrough(ff);
size_t count = iov_iter_count(iter);
ssize_t ret;
struct backing_file_ctx ctx = {
.cred = ff->cred,
.end_write = fuse_passthrough_end_write,
};
pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu\n", __func__,
backing_file, iocb->ki_pos, count);
if (!count)
return 0;
inode_lock(inode);
ret = backing_file_write_iter(backing_file, iter, iocb, iocb->ki_flags,
&ctx);
inode_unlock(inode);
return ret;
}
ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe,
size_t len, unsigned int flags)
{
struct fuse_file *ff = in->private_data;
struct file *backing_file = fuse_file_passthrough(ff);
struct backing_file_ctx ctx = {
.cred = ff->cred,
.accessed = fuse_file_accessed,
};
struct kiocb iocb;
ssize_t ret;
pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
backing_file, *ppos, len, flags);
init_sync_kiocb(&iocb, in);
iocb.ki_pos = *ppos;
ret = backing_file_splice_read(backing_file, &iocb, pipe, len, flags, &ctx);
*ppos = iocb.ki_pos;
return ret;
}
ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
struct file *out, loff_t *ppos,
size_t len, unsigned int flags)
{
struct fuse_file *ff = out->private_data;
struct file *backing_file = fuse_file_passthrough(ff);
struct inode *inode = file_inode(out);
ssize_t ret;
struct backing_file_ctx ctx = {
.cred = ff->cred,
.end_write = fuse_passthrough_end_write,
};
struct kiocb iocb;
pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
backing_file, *ppos, len, flags);
inode_lock(inode);
init_sync_kiocb(&iocb, out);
iocb.ki_pos = *ppos;
ret = backing_file_splice_write(pipe, backing_file, &iocb, len, flags, &ctx);
*ppos = iocb.ki_pos;
inode_unlock(inode);
return ret;
}
ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma)
{
struct fuse_file *ff = file->private_data;
struct file *backing_file = fuse_file_passthrough(ff);
struct backing_file_ctx ctx = {
.cred = ff->cred,
.accessed = fuse_file_accessed,
};
pr_debug("%s: backing_file=0x%p, start=%lu, end=%lu\n", __func__,
backing_file, vma->vm_start, vma->vm_end);
return backing_file_mmap(backing_file, vma, &ctx);
}
/*
* Setup passthrough to a backing file.
*
* Returns an fb object with elevated refcount to be stored in fuse inode.
*/
struct fuse_backing *fuse_passthrough_open(struct file *file, int backing_id)
{
struct fuse_file *ff = file->private_data;
struct fuse_conn *fc = ff->fm->fc;
struct fuse_backing *fb = NULL;
struct file *backing_file;
int err;
err = -EINVAL;
if (backing_id <= 0)
goto out;
err = -ENOENT;
fb = fuse_backing_lookup(fc, backing_id);
if (!fb)
goto out;
/* Allocate backing file per fuse file to store fuse path */
backing_file = backing_file_open(&file->f_path, file->f_flags,
&fb->file->f_path, fb->cred);
err = PTR_ERR(backing_file);
if (IS_ERR(backing_file)) {
fuse_backing_put(fb);
goto out;
}
err = 0;
ff->passthrough = backing_file;
ff->cred = get_cred(fb->cred);
out:
pr_debug("%s: backing_id=%d, fb=0x%p, backing_file=0x%p, err=%i\n", __func__,
backing_id, fb, ff->passthrough, err);
return err ? ERR_PTR(err) : fb;
}
void fuse_passthrough_release(struct fuse_file *ff, struct fuse_backing *fb)
{
pr_debug("%s: fb=0x%p, backing_file=0x%p\n", __func__,
fb, ff->passthrough);
fput(ff->passthrough);
ff->passthrough = NULL;
put_cred(ff->cred);
ff->cred = NULL;
}
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