This commit fills in read/write/mmap handling for famfs files. The
dev_dax_iomap interface is used - just like xfs in fs-dax mode.
Signed-off-by: John Groves <john@groves.net>
---
fs/fuse/famfs.c | 436 +++++++++++++++++++++++++++++++++++++++++++++++
fs/fuse/file.c | 14 ++
fs/fuse/fuse_i.h | 3 +
3 files changed, 453 insertions(+)
diff --git a/fs/fuse/famfs.c b/fs/fuse/famfs.c
index f5e01032b825..1973eb10b60b 100644
--- a/fs/fuse/famfs.c
+++ b/fs/fuse/famfs.c
@@ -585,3 +585,439 @@ famfs_file_init_dax(
return rc;
}
+/*********************************************************************
+ * iomap_operations
+ *
+ * This stuff uses the iomap (dax-related) helpers to resolve file offsets to
+ * offsets within a dax device.
+ */
+
+static ssize_t famfs_file_bad(struct inode *inode);
+
+static int
+famfs_interleave_fileofs_to_daxofs(struct inode *inode, struct iomap *iomap,
+ loff_t file_offset, off_t len, unsigned int flags)
+{
+ struct fuse_inode *fi = get_fuse_inode(inode);
+ struct famfs_file_meta *meta = fi->famfs_meta;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ loff_t local_offset = file_offset;
+ int i;
+
+ /* This function is only for extent_type INTERLEAVED_EXTENT */
+ if (meta->fm_extent_type != INTERLEAVED_EXTENT) {
+ pr_err("%s: bad extent type\n", __func__);
+ goto err_out;
+ }
+
+ if (famfs_file_bad(inode))
+ goto err_out;
+
+ iomap->offset = file_offset;
+
+ for (i = 0; i < meta->fm_niext; i++) {
+ struct famfs_meta_interleaved_ext *fei = &meta->ie[i];
+ u64 chunk_size = fei->fie_chunk_size;
+ u64 nstrips = fei->fie_nstrips;
+ u64 ext_size = fei->fie_nbytes;
+
+ ext_size = min_t(u64, ext_size, meta->file_size);
+
+ if (ext_size == 0) {
+ pr_err("%s: ext_size=%lld file_size=%ld\n",
+ __func__, fei->fie_nbytes, meta->file_size);
+ goto err_out;
+ }
+
+ /* Is the data is in this striped extent? */
+ if (local_offset < ext_size) {
+ u64 chunk_num = local_offset / chunk_size;
+ u64 chunk_offset = local_offset % chunk_size;
+ u64 stripe_num = chunk_num / nstrips;
+ u64 strip_num = chunk_num % nstrips;
+ u64 chunk_remainder = chunk_size - chunk_offset;
+ u64 strip_offset = chunk_offset + (stripe_num * chunk_size);
+ u64 strip_dax_ofs = fei->ie_strips[strip_num].ext_offset;
+ u64 strip_devidx = fei->ie_strips[strip_num].dev_index;
+
+ if (!fc->dax_devlist->devlist[strip_devidx].valid) {
+ pr_err("%s: daxdev=%lld invalid\n", __func__,
+ strip_devidx);
+ goto err_out;
+ }
+ iomap->addr = strip_dax_ofs + strip_offset;
+ iomap->offset = file_offset;
+ iomap->length = min_t(loff_t, len, chunk_remainder);
+
+ iomap->dax_dev = fc->dax_devlist->devlist[strip_devidx].devp;
+
+ iomap->type = IOMAP_MAPPED;
+ iomap->flags = flags;
+
+ return 0;
+ }
+ local_offset -= ext_size; /* offset is beyond this striped extent */
+ }
+
+ err_out:
+ pr_err("%s: err_out\n", __func__);
+
+ /* We fell out the end of the extent list.
+ * Set iomap to zero length in this case, and return 0
+ * This just means that the r/w is past EOF
+ */
+ iomap->addr = 0; /* there is no valid dax device offset */
+ iomap->offset = file_offset; /* file offset */
+ iomap->length = 0; /* this had better result in no access to dax mem */
+ iomap->dax_dev = NULL;
+ iomap->type = IOMAP_MAPPED;
+ iomap->flags = flags;
+
+ return 0;
+}
+
+/**
+ * famfs_fileofs_to_daxofs() - Resolve (file, offset, len) to (daxdev, offset, len)
+ *
+ * This function is called by famfs_fuse_iomap_begin() to resolve an offset in a
+ * file to an offset in a dax device. This is upcalled from dax from calls to
+ * both * dax_iomap_fault() and dax_iomap_rw(). Dax finishes the job resolving
+ * a fault to a specific physical page (the fault case) or doing a memcpy
+ * variant (the rw case)
+ *
+ * Pages can be PTE (4k), PMD (2MiB) or (theoretically) PuD (1GiB)
+ * (these sizes are for X86; may vary on other cpu architectures
+ *
+ * @inode: The file where the fault occurred
+ * @iomap: To be filled in to indicate where to find the right memory,
+ * relative to a dax device.
+ * @file_offset: Within the file where the fault occurred (will be page boundary)
+ * @len: The length of the faulted mapping (will be a page multiple)
+ * (will be trimmed in *iomap if it's disjoint in the extent list)
+ * @flags:
+ *
+ * Return values: 0. (info is returned in a modified @iomap struct)
+ */
+static int
+famfs_fileofs_to_daxofs(struct inode *inode, struct iomap *iomap,
+ loff_t file_offset, off_t len, unsigned int flags)
+{
+ struct fuse_inode *fi = get_fuse_inode(inode);
+ struct famfs_file_meta *meta = fi->famfs_meta;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ loff_t local_offset = file_offset;
+ int i;
+
+ if (!fc->dax_devlist) {
+ pr_err("%s: null dax_devlist\n", __func__);
+ goto err_out;
+ }
+
+ if (famfs_file_bad(inode))
+ goto err_out;
+
+ if (meta->fm_extent_type == INTERLEAVED_EXTENT)
+ return famfs_interleave_fileofs_to_daxofs(inode, iomap,
+ file_offset,
+ len, flags);
+
+ iomap->offset = file_offset;
+
+ for (i = 0; i < meta->fm_nextents; i++) {
+ /* TODO: check devindex too */
+ loff_t dax_ext_offset = meta->se[i].ext_offset;
+ loff_t dax_ext_len = meta->se[i].ext_len;
+ u64 daxdev_idx = meta->se[i].dev_index;
+
+ if ((dax_ext_offset == 0) &&
+ (meta->file_type != FAMFS_SUPERBLOCK))
+ pr_warn("%s: zero offset on non-superblock file!!\n",
+ __func__);
+
+ /* local_offset is the offset minus the size of extents skipped
+ * so far; If local_offset < dax_ext_len, the data of interest
+ * starts in this extent
+ */
+ if (local_offset < dax_ext_len) {
+ loff_t ext_len_remainder = dax_ext_len - local_offset;
+ struct famfs_daxdev *dd;
+
+ dd = &fc->dax_devlist->devlist[daxdev_idx];
+
+ if (!dd->valid || dd->error) {
+ pr_err("%s: daxdev=%lld %s\n", __func__,
+ daxdev_idx,
+ dd->valid ? "error" : "invalid");
+ goto err_out;
+ }
+
+ /*
+ * OK, we found the file metadata extent where this
+ * data begins
+ * @local_offset - The offset within the current
+ * extent
+ * @ext_len_remainder - Remaining length of ext after
+ * skipping local_offset
+ * Outputs:
+ * iomap->addr: the offset within the dax device where
+ * the data starts
+ * iomap->offset: the file offset
+ * iomap->length: the valid length resolved here
+ */
+ iomap->addr = dax_ext_offset + local_offset;
+ iomap->offset = file_offset;
+ iomap->length = min_t(loff_t, len, ext_len_remainder);
+
+ iomap->dax_dev = fc->dax_devlist->devlist[daxdev_idx].devp;
+
+ iomap->type = IOMAP_MAPPED;
+ iomap->flags = flags;
+ return 0;
+ }
+ local_offset -= dax_ext_len; /* Get ready for the next extent */
+ }
+
+ err_out:
+ pr_err("%s: err_out\n", __func__);
+
+ /* We fell out the end of the extent list.
+ * Set iomap to zero length in this case, and return 0
+ * This just means that the r/w is past EOF
+ */
+ iomap->addr = 0; /* there is no valid dax device offset */
+ iomap->offset = file_offset; /* file offset */
+ iomap->length = 0; /* this had better result in no access to dax mem */
+ iomap->dax_dev = NULL;
+ iomap->type = IOMAP_MAPPED;
+ iomap->flags = flags;
+
+ return 0;
+}
+
+/**
+ * famfs_fuse_iomap_begin() - Handler for iomap_begin upcall from dax
+ *
+ * This function is pretty simple because files are
+ * * never partially allocated
+ * * never have holes (never sparse)
+ * * never "allocate on write"
+ *
+ * @inode: inode for the file being accessed
+ * @offset: offset within the file
+ * @length: Length being accessed at offset
+ * @flags:
+ * @iomap: iomap struct to be filled in, resolving (offset, length) to
+ * (daxdev, offset, len)
+ * @srcmap:
+ */
+static int
+famfs_fuse_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
+ unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
+{
+ struct fuse_inode *fi = get_fuse_inode(inode);
+ struct famfs_file_meta *meta = fi->famfs_meta;
+ size_t size;
+
+ size = i_size_read(inode);
+
+ WARN_ON(size != meta->file_size);
+
+ return famfs_fileofs_to_daxofs(inode, iomap, offset, length, flags);
+}
+
+/* Note: We never need a special set of write_iomap_ops because famfs never
+ * performs allocation on write.
+ */
+const struct iomap_ops famfs_iomap_ops = {
+ .iomap_begin = famfs_fuse_iomap_begin,
+};
+
+/*********************************************************************
+ * vm_operations
+ */
+static vm_fault_t
+__famfs_fuse_filemap_fault(struct vm_fault *vmf, unsigned int pe_size,
+ bool write_fault)
+{
+ struct inode *inode = file_inode(vmf->vma->vm_file);
+ vm_fault_t ret;
+ pfn_t pfn;
+
+ if (!IS_DAX(file_inode(vmf->vma->vm_file))) {
+ pr_err("%s: file not marked IS_DAX!!\n", __func__);
+ return VM_FAULT_SIGBUS;
+ }
+
+ if (write_fault) {
+ sb_start_pagefault(inode->i_sb);
+ file_update_time(vmf->vma->vm_file);
+ }
+
+ ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &famfs_iomap_ops);
+ if (ret & VM_FAULT_NEEDDSYNC)
+ ret = dax_finish_sync_fault(vmf, pe_size, pfn);
+
+ if (write_fault)
+ sb_end_pagefault(inode->i_sb);
+
+ return ret;
+}
+
+static inline bool
+famfs_is_write_fault(struct vm_fault *vmf)
+{
+ return (vmf->flags & FAULT_FLAG_WRITE) &&
+ (vmf->vma->vm_flags & VM_SHARED);
+}
+
+static vm_fault_t
+famfs_filemap_fault(struct vm_fault *vmf)
+{
+ return __famfs_fuse_filemap_fault(vmf, 0, famfs_is_write_fault(vmf));
+}
+
+static vm_fault_t
+famfs_filemap_huge_fault(struct vm_fault *vmf, unsigned int pe_size)
+{
+ return __famfs_fuse_filemap_fault(vmf, pe_size, famfs_is_write_fault(vmf));
+}
+
+static vm_fault_t
+famfs_filemap_page_mkwrite(struct vm_fault *vmf)
+{
+ return __famfs_fuse_filemap_fault(vmf, 0, true);
+}
+
+static vm_fault_t
+famfs_filemap_pfn_mkwrite(struct vm_fault *vmf)
+{
+ return __famfs_fuse_filemap_fault(vmf, 0, true);
+}
+
+static vm_fault_t
+famfs_filemap_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff,
+ pgoff_t end_pgoff)
+{
+ return filemap_map_pages(vmf, start_pgoff, end_pgoff);
+}
+
+const struct vm_operations_struct famfs_file_vm_ops = {
+ .fault = famfs_filemap_fault,
+ .huge_fault = famfs_filemap_huge_fault,
+ .map_pages = famfs_filemap_map_pages,
+ .page_mkwrite = famfs_filemap_page_mkwrite,
+ .pfn_mkwrite = famfs_filemap_pfn_mkwrite,
+};
+
+/*********************************************************************
+ * file_operations
+ */
+
+/**
+ * famfs_file_bad() - Check for files that aren't in a valid state
+ *
+ * @inode - inode
+ *
+ * Returns: 0=success
+ * -errno=failure
+ */
+static ssize_t
+famfs_file_bad(struct inode *inode)
+{
+ struct fuse_inode *fi = get_fuse_inode(inode);
+ struct famfs_file_meta *meta = fi->famfs_meta;
+ size_t i_size = i_size_read(inode);
+
+ if (!meta) {
+ pr_err("%s: un-initialized famfs file\n", __func__);
+ return -EIO;
+ }
+ if (meta->error) {
+ pr_debug("%s: previously detected metadata errors\n", __func__);
+ return -EIO;
+ }
+ if (i_size != meta->file_size) {
+ pr_warn("%s: i_size overwritten from %ld to %ld\n",
+ __func__, meta->file_size, i_size);
+ meta->error = true;
+ return -ENXIO;
+ }
+ if (!IS_DAX(inode)) {
+ pr_debug("%s: inode %llx IS_DAX is false\n", __func__, (u64)inode);
+ return -ENXIO;
+ }
+ return 0;
+}
+
+static ssize_t
+famfs_fuse_rw_prep(struct kiocb *iocb, struct iov_iter *ubuf)
+{
+ struct inode *inode = iocb->ki_filp->f_mapping->host;
+ size_t i_size = i_size_read(inode);
+ size_t count = iov_iter_count(ubuf);
+ size_t max_count;
+ ssize_t rc;
+
+ rc = famfs_file_bad(inode);
+ if (rc)
+ return rc;
+
+ max_count = max_t(size_t, 0, i_size - iocb->ki_pos);
+
+ if (count > max_count)
+ iov_iter_truncate(ubuf, max_count);
+
+ if (!iov_iter_count(ubuf))
+ return 0;
+
+ return rc;
+}
+
+ssize_t
+famfs_fuse_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ ssize_t rc;
+
+ rc = famfs_fuse_rw_prep(iocb, to);
+ if (rc)
+ return rc;
+
+ if (!iov_iter_count(to))
+ return 0;
+
+ rc = dax_iomap_rw(iocb, to, &famfs_iomap_ops);
+
+ file_accessed(iocb->ki_filp);
+ return rc;
+}
+
+ssize_t
+famfs_fuse_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ ssize_t rc;
+
+ rc = famfs_fuse_rw_prep(iocb, from);
+ if (rc)
+ return rc;
+
+ if (!iov_iter_count(from))
+ return 0;
+
+ return dax_iomap_rw(iocb, from, &famfs_iomap_ops);
+}
+
+int
+famfs_fuse_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct inode *inode = file_inode(file);
+ ssize_t rc;
+
+ rc = famfs_file_bad(inode);
+ if (rc)
+ return (int)rc;
+
+ file_accessed(file);
+ vma->vm_ops = &famfs_file_vm_ops;
+ vm_flags_set(vma, VM_HUGEPAGE);
+ return 0;
+}
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 5d205eadb48f..24a14b176510 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1874,6 +1874,8 @@ static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
if (FUSE_IS_VIRTIO_DAX(fi))
return fuse_dax_read_iter(iocb, to);
+ if (fuse_file_famfs(fi))
+ return famfs_fuse_read_iter(iocb, to);
/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
if (ff->open_flags & FOPEN_DIRECT_IO)
@@ -1896,6 +1898,8 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (FUSE_IS_VIRTIO_DAX(fi))
return fuse_dax_write_iter(iocb, from);
+ if (fuse_file_famfs(fi))
+ return famfs_fuse_write_iter(iocb, from);
/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
if (ff->open_flags & FOPEN_DIRECT_IO)
@@ -1911,10 +1915,14 @@ static ssize_t fuse_splice_read(struct file *in, loff_t *ppos,
unsigned int flags)
{
struct fuse_file *ff = in->private_data;
+ struct inode *inode = file_inode(in);
+ struct fuse_inode *fi = get_fuse_inode(inode);
/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
return fuse_passthrough_splice_read(in, ppos, pipe, len, flags);
+ else if (fuse_file_famfs(fi))
+ return -EIO; /* direct I/O doesn't make sense in dax_iomap */
else
return filemap_splice_read(in, ppos, pipe, len, flags);
}
@@ -1923,10 +1931,14 @@ static ssize_t fuse_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 inode *inode = file_inode(out);
+ struct fuse_inode *fi = get_fuse_inode(inode);
/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
return fuse_passthrough_splice_write(pipe, out, ppos, len, flags);
+ else if (fuse_file_famfs(fi))
+ return -EIO; /* direct I/O doesn't make sense in dax_iomap */
else
return iter_file_splice_write(pipe, out, ppos, len, flags);
}
@@ -2732,6 +2744,8 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
/* DAX mmap is superior to direct_io mmap */
if (FUSE_IS_VIRTIO_DAX(fi))
return fuse_dax_mmap(file, vma);
+ if (fuse_file_famfs(fi))
+ return famfs_fuse_mmap(file, vma);
/*
* If inode is in passthrough io mode, because it has some file open
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 37298551539c..3b3a1d95367f 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1564,6 +1564,9 @@ extern void fuse_sysctl_unregister(void);
int famfs_file_init_dax(struct fuse_mount *fm,
struct inode *inode, void *fmap_buf,
size_t fmap_size);
+ssize_t famfs_fuse_write_iter(struct kiocb *iocb, struct iov_iter *from);
+ssize_t famfs_fuse_read_iter(struct kiocb *iocb, struct iov_iter *to);
+int famfs_fuse_mmap(struct file *file, struct vm_area_struct *vma);
void __famfs_meta_free(void *map);
void famfs_teardown(struct fuse_conn *fc);
#endif
--
2.49.0On Thu, Jul 3, 2025 at 8:51 PM John Groves <John@groves.net> wrote:
>
> This commit fills in read/write/mmap handling for famfs files. The
> dev_dax_iomap interface is used - just like xfs in fs-dax mode.
>
> Signed-off-by: John Groves <john@groves.net>
> ---
> fs/fuse/famfs.c | 436 +++++++++++++++++++++++++++++++++++++++++++++++
> fs/fuse/file.c | 14 ++
> fs/fuse/fuse_i.h | 3 +
> 3 files changed, 453 insertions(+)
>
> diff --git a/fs/fuse/famfs.c b/fs/fuse/famfs.c
> index f5e01032b825..1973eb10b60b 100644
> --- a/fs/fuse/famfs.c
> +++ b/fs/fuse/famfs.c
> @@ -585,3 +585,439 @@ famfs_file_init_dax(
> return rc;
> }
>
> +/*********************************************************************
> + * iomap_operations
> + *
> + * This stuff uses the iomap (dax-related) helpers to resolve file offsets to
> + * offsets within a dax device.
> + */
> +
> +static ssize_t famfs_file_bad(struct inode *inode);
> +
> +static int
> +famfs_interleave_fileofs_to_daxofs(struct inode *inode, struct iomap *iomap,
> + loff_t file_offset, off_t len, unsigned int flags)
> +{
> + struct fuse_inode *fi = get_fuse_inode(inode);
> + struct famfs_file_meta *meta = fi->famfs_meta;
> + struct fuse_conn *fc = get_fuse_conn(inode);
> + loff_t local_offset = file_offset;
> + int i;
> +
> + /* This function is only for extent_type INTERLEAVED_EXTENT */
> + if (meta->fm_extent_type != INTERLEAVED_EXTENT) {
> + pr_err("%s: bad extent type\n", __func__);
> + goto err_out;
> + }
> +
> + if (famfs_file_bad(inode))
> + goto err_out;
> +
> + iomap->offset = file_offset;
> +
> + for (i = 0; i < meta->fm_niext; i++) {
> + struct famfs_meta_interleaved_ext *fei = &meta->ie[i];
> + u64 chunk_size = fei->fie_chunk_size;
> + u64 nstrips = fei->fie_nstrips;
> + u64 ext_size = fei->fie_nbytes;
> +
> + ext_size = min_t(u64, ext_size, meta->file_size);
> +
> + if (ext_size == 0) {
> + pr_err("%s: ext_size=%lld file_size=%ld\n",
> + __func__, fei->fie_nbytes, meta->file_size);
> + goto err_out;
> + }
> +
> + /* Is the data is in this striped extent? */
> + if (local_offset < ext_size) {
> + u64 chunk_num = local_offset / chunk_size;
> + u64 chunk_offset = local_offset % chunk_size;
> + u64 stripe_num = chunk_num / nstrips;
> + u64 strip_num = chunk_num % nstrips;
> + u64 chunk_remainder = chunk_size - chunk_offset;
> + u64 strip_offset = chunk_offset + (stripe_num * chunk_size);
> + u64 strip_dax_ofs = fei->ie_strips[strip_num].ext_offset;
> + u64 strip_devidx = fei->ie_strips[strip_num].dev_index;
> +
> + if (!fc->dax_devlist->devlist[strip_devidx].valid) {
> + pr_err("%s: daxdev=%lld invalid\n", __func__,
> + strip_devidx);
> + goto err_out;
> + }
> + iomap->addr = strip_dax_ofs + strip_offset;
> + iomap->offset = file_offset;
> + iomap->length = min_t(loff_t, len, chunk_remainder);
> +
> + iomap->dax_dev = fc->dax_devlist->devlist[strip_devidx].devp;
> +
> + iomap->type = IOMAP_MAPPED;
> + iomap->flags = flags;
> +
> + return 0;
> + }
> + local_offset -= ext_size; /* offset is beyond this striped extent */
> + }
> +
> + err_out:
> + pr_err("%s: err_out\n", __func__);
> +
> + /* We fell out the end of the extent list.
> + * Set iomap to zero length in this case, and return 0
> + * This just means that the r/w is past EOF
> + */
> + iomap->addr = 0; /* there is no valid dax device offset */
> + iomap->offset = file_offset; /* file offset */
> + iomap->length = 0; /* this had better result in no access to dax mem */
> + iomap->dax_dev = NULL;
> + iomap->type = IOMAP_MAPPED;
> + iomap->flags = flags;
> +
> + return 0;
> +}
> +
> +/**
> + * famfs_fileofs_to_daxofs() - Resolve (file, offset, len) to (daxdev, offset, len)
> + *
> + * This function is called by famfs_fuse_iomap_begin() to resolve an offset in a
> + * file to an offset in a dax device. This is upcalled from dax from calls to
> + * both * dax_iomap_fault() and dax_iomap_rw(). Dax finishes the job resolving
> + * a fault to a specific physical page (the fault case) or doing a memcpy
> + * variant (the rw case)
> + *
> + * Pages can be PTE (4k), PMD (2MiB) or (theoretically) PuD (1GiB)
> + * (these sizes are for X86; may vary on other cpu architectures
> + *
> + * @inode: The file where the fault occurred
> + * @iomap: To be filled in to indicate where to find the right memory,
> + * relative to a dax device.
> + * @file_offset: Within the file where the fault occurred (will be page boundary)
> + * @len: The length of the faulted mapping (will be a page multiple)
> + * (will be trimmed in *iomap if it's disjoint in the extent list)
> + * @flags:
> + *
> + * Return values: 0. (info is returned in a modified @iomap struct)
> + */
> +static int
> +famfs_fileofs_to_daxofs(struct inode *inode, struct iomap *iomap,
> + loff_t file_offset, off_t len, unsigned int flags)
> +{
> + struct fuse_inode *fi = get_fuse_inode(inode);
> + struct famfs_file_meta *meta = fi->famfs_meta;
> + struct fuse_conn *fc = get_fuse_conn(inode);
> + loff_t local_offset = file_offset;
> + int i;
> +
> + if (!fc->dax_devlist) {
> + pr_err("%s: null dax_devlist\n", __func__);
> + goto err_out;
> + }
> +
> + if (famfs_file_bad(inode))
> + goto err_out;
> +
> + if (meta->fm_extent_type == INTERLEAVED_EXTENT)
> + return famfs_interleave_fileofs_to_daxofs(inode, iomap,
> + file_offset,
> + len, flags);
> +
> + iomap->offset = file_offset;
> +
> + for (i = 0; i < meta->fm_nextents; i++) {
> + /* TODO: check devindex too */
> + loff_t dax_ext_offset = meta->se[i].ext_offset;
> + loff_t dax_ext_len = meta->se[i].ext_len;
> + u64 daxdev_idx = meta->se[i].dev_index;
> +
> + if ((dax_ext_offset == 0) &&
> + (meta->file_type != FAMFS_SUPERBLOCK))
> + pr_warn("%s: zero offset on non-superblock file!!\n",
> + __func__);
> +
> + /* local_offset is the offset minus the size of extents skipped
> + * so far; If local_offset < dax_ext_len, the data of interest
> + * starts in this extent
> + */
> + if (local_offset < dax_ext_len) {
> + loff_t ext_len_remainder = dax_ext_len - local_offset;
> + struct famfs_daxdev *dd;
> +
> + dd = &fc->dax_devlist->devlist[daxdev_idx];
> +
> + if (!dd->valid || dd->error) {
> + pr_err("%s: daxdev=%lld %s\n", __func__,
> + daxdev_idx,
> + dd->valid ? "error" : "invalid");
> + goto err_out;
> + }
> +
> + /*
> + * OK, we found the file metadata extent where this
> + * data begins
> + * @local_offset - The offset within the current
> + * extent
> + * @ext_len_remainder - Remaining length of ext after
> + * skipping local_offset
> + * Outputs:
> + * iomap->addr: the offset within the dax device where
> + * the data starts
> + * iomap->offset: the file offset
> + * iomap->length: the valid length resolved here
> + */
> + iomap->addr = dax_ext_offset + local_offset;
> + iomap->offset = file_offset;
> + iomap->length = min_t(loff_t, len, ext_len_remainder);
> +
> + iomap->dax_dev = fc->dax_devlist->devlist[daxdev_idx].devp;
> +
> + iomap->type = IOMAP_MAPPED;
> + iomap->flags = flags;
> + return 0;
> + }
> + local_offset -= dax_ext_len; /* Get ready for the next extent */
> + }
> +
> + err_out:
> + pr_err("%s: err_out\n", __func__);
> +
> + /* We fell out the end of the extent list.
> + * Set iomap to zero length in this case, and return 0
> + * This just means that the r/w is past EOF
> + */
> + iomap->addr = 0; /* there is no valid dax device offset */
> + iomap->offset = file_offset; /* file offset */
> + iomap->length = 0; /* this had better result in no access to dax mem */
> + iomap->dax_dev = NULL;
> + iomap->type = IOMAP_MAPPED;
> + iomap->flags = flags;
> +
> + return 0;
> +}
> +
> +/**
> + * famfs_fuse_iomap_begin() - Handler for iomap_begin upcall from dax
> + *
> + * This function is pretty simple because files are
> + * * never partially allocated
> + * * never have holes (never sparse)
> + * * never "allocate on write"
> + *
> + * @inode: inode for the file being accessed
> + * @offset: offset within the file
> + * @length: Length being accessed at offset
> + * @flags:
> + * @iomap: iomap struct to be filled in, resolving (offset, length) to
> + * (daxdev, offset, len)
> + * @srcmap:
> + */
> +static int
> +famfs_fuse_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> + unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
> +{
> + struct fuse_inode *fi = get_fuse_inode(inode);
> + struct famfs_file_meta *meta = fi->famfs_meta;
> + size_t size;
> +
> + size = i_size_read(inode);
> +
> + WARN_ON(size != meta->file_size);
> +
> + return famfs_fileofs_to_daxofs(inode, iomap, offset, length, flags);
> +}
> +
> +/* Note: We never need a special set of write_iomap_ops because famfs never
> + * performs allocation on write.
> + */
> +const struct iomap_ops famfs_iomap_ops = {
> + .iomap_begin = famfs_fuse_iomap_begin,
> +};
> +
> +/*********************************************************************
> + * vm_operations
> + */
> +static vm_fault_t
> +__famfs_fuse_filemap_fault(struct vm_fault *vmf, unsigned int pe_size,
> + bool write_fault)
> +{
> + struct inode *inode = file_inode(vmf->vma->vm_file);
> + vm_fault_t ret;
> + pfn_t pfn;
> +
> + if (!IS_DAX(file_inode(vmf->vma->vm_file))) {
> + pr_err("%s: file not marked IS_DAX!!\n", __func__);
> + return VM_FAULT_SIGBUS;
> + }
> +
> + if (write_fault) {
> + sb_start_pagefault(inode->i_sb);
> + file_update_time(vmf->vma->vm_file);
> + }
> +
> + ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &famfs_iomap_ops);
> + if (ret & VM_FAULT_NEEDDSYNC)
> + ret = dax_finish_sync_fault(vmf, pe_size, pfn);
> +
> + if (write_fault)
> + sb_end_pagefault(inode->i_sb);
> +
> + return ret;
> +}
> +
> +static inline bool
> +famfs_is_write_fault(struct vm_fault *vmf)
> +{
> + return (vmf->flags & FAULT_FLAG_WRITE) &&
> + (vmf->vma->vm_flags & VM_SHARED);
> +}
> +
> +static vm_fault_t
> +famfs_filemap_fault(struct vm_fault *vmf)
> +{
> + return __famfs_fuse_filemap_fault(vmf, 0, famfs_is_write_fault(vmf));
> +}
> +
> +static vm_fault_t
> +famfs_filemap_huge_fault(struct vm_fault *vmf, unsigned int pe_size)
> +{
> + return __famfs_fuse_filemap_fault(vmf, pe_size, famfs_is_write_fault(vmf));
> +}
> +
> +static vm_fault_t
> +famfs_filemap_page_mkwrite(struct vm_fault *vmf)
> +{
> + return __famfs_fuse_filemap_fault(vmf, 0, true);
> +}
> +
> +static vm_fault_t
> +famfs_filemap_pfn_mkwrite(struct vm_fault *vmf)
> +{
> + return __famfs_fuse_filemap_fault(vmf, 0, true);
> +}
> +
> +static vm_fault_t
> +famfs_filemap_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff,
> + pgoff_t end_pgoff)
> +{
> + return filemap_map_pages(vmf, start_pgoff, end_pgoff);
> +}
> +
> +const struct vm_operations_struct famfs_file_vm_ops = {
> + .fault = famfs_filemap_fault,
> + .huge_fault = famfs_filemap_huge_fault,
> + .map_pages = famfs_filemap_map_pages,
> + .page_mkwrite = famfs_filemap_page_mkwrite,
> + .pfn_mkwrite = famfs_filemap_pfn_mkwrite,
> +};
> +
> +/*********************************************************************
> + * file_operations
> + */
> +
> +/**
> + * famfs_file_bad() - Check for files that aren't in a valid state
> + *
> + * @inode - inode
> + *
> + * Returns: 0=success
> + * -errno=failure
> + */
> +static ssize_t
> +famfs_file_bad(struct inode *inode)
> +{
> + struct fuse_inode *fi = get_fuse_inode(inode);
> + struct famfs_file_meta *meta = fi->famfs_meta;
> + size_t i_size = i_size_read(inode);
> +
> + if (!meta) {
> + pr_err("%s: un-initialized famfs file\n", __func__);
> + return -EIO;
> + }
> + if (meta->error) {
> + pr_debug("%s: previously detected metadata errors\n", __func__);
> + return -EIO;
> + }
> + if (i_size != meta->file_size) {
> + pr_warn("%s: i_size overwritten from %ld to %ld\n",
> + __func__, meta->file_size, i_size);
> + meta->error = true;
> + return -ENXIO;
> + }
> + if (!IS_DAX(inode)) {
> + pr_debug("%s: inode %llx IS_DAX is false\n", __func__, (u64)inode);
> + return -ENXIO;
> + }
> + return 0;
> +}
> +
> +static ssize_t
> +famfs_fuse_rw_prep(struct kiocb *iocb, struct iov_iter *ubuf)
> +{
> + struct inode *inode = iocb->ki_filp->f_mapping->host;
> + size_t i_size = i_size_read(inode);
> + size_t count = iov_iter_count(ubuf);
> + size_t max_count;
> + ssize_t rc;
> +
> + rc = famfs_file_bad(inode);
> + if (rc)
> + return rc;
> +
> + max_count = max_t(size_t, 0, i_size - iocb->ki_pos);
> +
> + if (count > max_count)
> + iov_iter_truncate(ubuf, max_count);
> +
> + if (!iov_iter_count(ubuf))
> + return 0;
> +
> + return rc;
> +}
> +
> +ssize_t
> +famfs_fuse_read_iter(struct kiocb *iocb, struct iov_iter *to)
> +{
> + ssize_t rc;
> +
> + rc = famfs_fuse_rw_prep(iocb, to);
> + if (rc)
> + return rc;
> +
> + if (!iov_iter_count(to))
> + return 0;
> +
> + rc = dax_iomap_rw(iocb, to, &famfs_iomap_ops);
> +
> + file_accessed(iocb->ki_filp);
> + return rc;
> +}
> +
> +ssize_t
> +famfs_fuse_write_iter(struct kiocb *iocb, struct iov_iter *from)
> +{
> + ssize_t rc;
> +
> + rc = famfs_fuse_rw_prep(iocb, from);
> + if (rc)
> + return rc;
> +
> + if (!iov_iter_count(from))
> + return 0;
> +
> + return dax_iomap_rw(iocb, from, &famfs_iomap_ops);
> +}
> +
> +int
> +famfs_fuse_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> + struct inode *inode = file_inode(file);
> + ssize_t rc;
> +
> + rc = famfs_file_bad(inode);
> + if (rc)
> + return (int)rc;
> +
> + file_accessed(file);
> + vma->vm_ops = &famfs_file_vm_ops;
> + vm_flags_set(vma, VM_HUGEPAGE);
> + return 0;
> +}
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 5d205eadb48f..24a14b176510 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1874,6 +1874,8 @@ static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
>
> if (FUSE_IS_VIRTIO_DAX(fi))
> return fuse_dax_read_iter(iocb, to);
> + if (fuse_file_famfs(fi))
> + return famfs_fuse_read_iter(iocb, to);
>
> /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> if (ff->open_flags & FOPEN_DIRECT_IO)
> @@ -1896,6 +1898,8 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>
> if (FUSE_IS_VIRTIO_DAX(fi))
> return fuse_dax_write_iter(iocb, from);
> + if (fuse_file_famfs(fi))
> + return famfs_fuse_write_iter(iocb, from);
>
> /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> if (ff->open_flags & FOPEN_DIRECT_IO)
> @@ -1911,10 +1915,14 @@ static ssize_t fuse_splice_read(struct file *in, loff_t *ppos,
> unsigned int flags)
> {
> struct fuse_file *ff = in->private_data;
> + struct inode *inode = file_inode(in);
> + struct fuse_inode *fi = get_fuse_inode(inode);
>
> /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
> return fuse_passthrough_splice_read(in, ppos, pipe, len, flags);
> + else if (fuse_file_famfs(fi))
> + return -EIO; /* direct I/O doesn't make sense in dax_iomap */
> else
> return filemap_splice_read(in, ppos, pipe, len, flags);
> }
> @@ -1923,10 +1931,14 @@ static ssize_t fuse_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 inode *inode = file_inode(out);
> + struct fuse_inode *fi = get_fuse_inode(inode);
>
> /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
> return fuse_passthrough_splice_write(pipe, out, ppos, len, flags);
> + else if (fuse_file_famfs(fi))
> + return -EIO; /* direct I/O doesn't make sense in dax_iomap */
> else
> return iter_file_splice_write(pipe, out, ppos, len, flags);
> }
This looks odd.
Usually, the methods first check for FUSE_IS_VIRTIO_DAX() and
fuse_file_famfs() to get this condition out of the way so I never needed
to think about whether or not the code verifies that fuse_file_passthrough()
and fuse_file_famfs() cannot co-exist.
Is there a reason why you did not follow the same pattern here?
Also, your comment makes no sense.
splice is not the case of direct I/O - quite the contrary.
Thanks,
Amir.
On 25/07/04 11:13AM, Amir Goldstein wrote:
> On Thu, Jul 3, 2025 at 8:51 PM John Groves <John@groves.net> wrote:
> >
> > This commit fills in read/write/mmap handling for famfs files. The
> > dev_dax_iomap interface is used - just like xfs in fs-dax mode.
> >
> > Signed-off-by: John Groves <john@groves.net>
> > ---
> > fs/fuse/famfs.c | 436 +++++++++++++++++++++++++++++++++++++++++++++++
> > fs/fuse/file.c | 14 ++
> > fs/fuse/fuse_i.h | 3 +
> > 3 files changed, 453 insertions(+)
> >
> > diff --git a/fs/fuse/famfs.c b/fs/fuse/famfs.c
> > index f5e01032b825..1973eb10b60b 100644
> > --- a/fs/fuse/famfs.c
> > +++ b/fs/fuse/famfs.c
> > @@ -585,3 +585,439 @@ famfs_file_init_dax(
> > return rc;
> > }
> >
> > +/*********************************************************************
> > + * iomap_operations
> > + *
> > + * This stuff uses the iomap (dax-related) helpers to resolve file offsets to
> > + * offsets within a dax device.
> > + */
> > +
> > +static ssize_t famfs_file_bad(struct inode *inode);
> > +
> > +static int
> > +famfs_interleave_fileofs_to_daxofs(struct inode *inode, struct iomap *iomap,
> > + loff_t file_offset, off_t len, unsigned int flags)
> > +{
> > + struct fuse_inode *fi = get_fuse_inode(inode);
> > + struct famfs_file_meta *meta = fi->famfs_meta;
> > + struct fuse_conn *fc = get_fuse_conn(inode);
> > + loff_t local_offset = file_offset;
> > + int i;
> > +
> > + /* This function is only for extent_type INTERLEAVED_EXTENT */
> > + if (meta->fm_extent_type != INTERLEAVED_EXTENT) {
> > + pr_err("%s: bad extent type\n", __func__);
> > + goto err_out;
> > + }
> > +
> > + if (famfs_file_bad(inode))
> > + goto err_out;
> > +
> > + iomap->offset = file_offset;
> > +
> > + for (i = 0; i < meta->fm_niext; i++) {
> > + struct famfs_meta_interleaved_ext *fei = &meta->ie[i];
> > + u64 chunk_size = fei->fie_chunk_size;
> > + u64 nstrips = fei->fie_nstrips;
> > + u64 ext_size = fei->fie_nbytes;
> > +
> > + ext_size = min_t(u64, ext_size, meta->file_size);
> > +
> > + if (ext_size == 0) {
> > + pr_err("%s: ext_size=%lld file_size=%ld\n",
> > + __func__, fei->fie_nbytes, meta->file_size);
> > + goto err_out;
> > + }
> > +
> > + /* Is the data is in this striped extent? */
> > + if (local_offset < ext_size) {
> > + u64 chunk_num = local_offset / chunk_size;
> > + u64 chunk_offset = local_offset % chunk_size;
> > + u64 stripe_num = chunk_num / nstrips;
> > + u64 strip_num = chunk_num % nstrips;
> > + u64 chunk_remainder = chunk_size - chunk_offset;
> > + u64 strip_offset = chunk_offset + (stripe_num * chunk_size);
> > + u64 strip_dax_ofs = fei->ie_strips[strip_num].ext_offset;
> > + u64 strip_devidx = fei->ie_strips[strip_num].dev_index;
> > +
> > + if (!fc->dax_devlist->devlist[strip_devidx].valid) {
> > + pr_err("%s: daxdev=%lld invalid\n", __func__,
> > + strip_devidx);
> > + goto err_out;
> > + }
> > + iomap->addr = strip_dax_ofs + strip_offset;
> > + iomap->offset = file_offset;
> > + iomap->length = min_t(loff_t, len, chunk_remainder);
> > +
> > + iomap->dax_dev = fc->dax_devlist->devlist[strip_devidx].devp;
> > +
> > + iomap->type = IOMAP_MAPPED;
> > + iomap->flags = flags;
> > +
> > + return 0;
> > + }
> > + local_offset -= ext_size; /* offset is beyond this striped extent */
> > + }
> > +
> > + err_out:
> > + pr_err("%s: err_out\n", __func__);
> > +
> > + /* We fell out the end of the extent list.
> > + * Set iomap to zero length in this case, and return 0
> > + * This just means that the r/w is past EOF
> > + */
> > + iomap->addr = 0; /* there is no valid dax device offset */
> > + iomap->offset = file_offset; /* file offset */
> > + iomap->length = 0; /* this had better result in no access to dax mem */
> > + iomap->dax_dev = NULL;
> > + iomap->type = IOMAP_MAPPED;
> > + iomap->flags = flags;
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * famfs_fileofs_to_daxofs() - Resolve (file, offset, len) to (daxdev, offset, len)
> > + *
> > + * This function is called by famfs_fuse_iomap_begin() to resolve an offset in a
> > + * file to an offset in a dax device. This is upcalled from dax from calls to
> > + * both * dax_iomap_fault() and dax_iomap_rw(). Dax finishes the job resolving
> > + * a fault to a specific physical page (the fault case) or doing a memcpy
> > + * variant (the rw case)
> > + *
> > + * Pages can be PTE (4k), PMD (2MiB) or (theoretically) PuD (1GiB)
> > + * (these sizes are for X86; may vary on other cpu architectures
> > + *
> > + * @inode: The file where the fault occurred
> > + * @iomap: To be filled in to indicate where to find the right memory,
> > + * relative to a dax device.
> > + * @file_offset: Within the file where the fault occurred (will be page boundary)
> > + * @len: The length of the faulted mapping (will be a page multiple)
> > + * (will be trimmed in *iomap if it's disjoint in the extent list)
> > + * @flags:
> > + *
> > + * Return values: 0. (info is returned in a modified @iomap struct)
> > + */
> > +static int
> > +famfs_fileofs_to_daxofs(struct inode *inode, struct iomap *iomap,
> > + loff_t file_offset, off_t len, unsigned int flags)
> > +{
> > + struct fuse_inode *fi = get_fuse_inode(inode);
> > + struct famfs_file_meta *meta = fi->famfs_meta;
> > + struct fuse_conn *fc = get_fuse_conn(inode);
> > + loff_t local_offset = file_offset;
> > + int i;
> > +
> > + if (!fc->dax_devlist) {
> > + pr_err("%s: null dax_devlist\n", __func__);
> > + goto err_out;
> > + }
> > +
> > + if (famfs_file_bad(inode))
> > + goto err_out;
> > +
> > + if (meta->fm_extent_type == INTERLEAVED_EXTENT)
> > + return famfs_interleave_fileofs_to_daxofs(inode, iomap,
> > + file_offset,
> > + len, flags);
> > +
> > + iomap->offset = file_offset;
> > +
> > + for (i = 0; i < meta->fm_nextents; i++) {
> > + /* TODO: check devindex too */
> > + loff_t dax_ext_offset = meta->se[i].ext_offset;
> > + loff_t dax_ext_len = meta->se[i].ext_len;
> > + u64 daxdev_idx = meta->se[i].dev_index;
> > +
> > + if ((dax_ext_offset == 0) &&
> > + (meta->file_type != FAMFS_SUPERBLOCK))
> > + pr_warn("%s: zero offset on non-superblock file!!\n",
> > + __func__);
> > +
> > + /* local_offset is the offset minus the size of extents skipped
> > + * so far; If local_offset < dax_ext_len, the data of interest
> > + * starts in this extent
> > + */
> > + if (local_offset < dax_ext_len) {
> > + loff_t ext_len_remainder = dax_ext_len - local_offset;
> > + struct famfs_daxdev *dd;
> > +
> > + dd = &fc->dax_devlist->devlist[daxdev_idx];
> > +
> > + if (!dd->valid || dd->error) {
> > + pr_err("%s: daxdev=%lld %s\n", __func__,
> > + daxdev_idx,
> > + dd->valid ? "error" : "invalid");
> > + goto err_out;
> > + }
> > +
> > + /*
> > + * OK, we found the file metadata extent where this
> > + * data begins
> > + * @local_offset - The offset within the current
> > + * extent
> > + * @ext_len_remainder - Remaining length of ext after
> > + * skipping local_offset
> > + * Outputs:
> > + * iomap->addr: the offset within the dax device where
> > + * the data starts
> > + * iomap->offset: the file offset
> > + * iomap->length: the valid length resolved here
> > + */
> > + iomap->addr = dax_ext_offset + local_offset;
> > + iomap->offset = file_offset;
> > + iomap->length = min_t(loff_t, len, ext_len_remainder);
> > +
> > + iomap->dax_dev = fc->dax_devlist->devlist[daxdev_idx].devp;
> > +
> > + iomap->type = IOMAP_MAPPED;
> > + iomap->flags = flags;
> > + return 0;
> > + }
> > + local_offset -= dax_ext_len; /* Get ready for the next extent */
> > + }
> > +
> > + err_out:
> > + pr_err("%s: err_out\n", __func__);
> > +
> > + /* We fell out the end of the extent list.
> > + * Set iomap to zero length in this case, and return 0
> > + * This just means that the r/w is past EOF
> > + */
> > + iomap->addr = 0; /* there is no valid dax device offset */
> > + iomap->offset = file_offset; /* file offset */
> > + iomap->length = 0; /* this had better result in no access to dax mem */
> > + iomap->dax_dev = NULL;
> > + iomap->type = IOMAP_MAPPED;
> > + iomap->flags = flags;
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * famfs_fuse_iomap_begin() - Handler for iomap_begin upcall from dax
> > + *
> > + * This function is pretty simple because files are
> > + * * never partially allocated
> > + * * never have holes (never sparse)
> > + * * never "allocate on write"
> > + *
> > + * @inode: inode for the file being accessed
> > + * @offset: offset within the file
> > + * @length: Length being accessed at offset
> > + * @flags:
> > + * @iomap: iomap struct to be filled in, resolving (offset, length) to
> > + * (daxdev, offset, len)
> > + * @srcmap:
> > + */
> > +static int
> > +famfs_fuse_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> > + unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
> > +{
> > + struct fuse_inode *fi = get_fuse_inode(inode);
> > + struct famfs_file_meta *meta = fi->famfs_meta;
> > + size_t size;
> > +
> > + size = i_size_read(inode);
> > +
> > + WARN_ON(size != meta->file_size);
> > +
> > + return famfs_fileofs_to_daxofs(inode, iomap, offset, length, flags);
> > +}
> > +
> > +/* Note: We never need a special set of write_iomap_ops because famfs never
> > + * performs allocation on write.
> > + */
> > +const struct iomap_ops famfs_iomap_ops = {
> > + .iomap_begin = famfs_fuse_iomap_begin,
> > +};
> > +
> > +/*********************************************************************
> > + * vm_operations
> > + */
> > +static vm_fault_t
> > +__famfs_fuse_filemap_fault(struct vm_fault *vmf, unsigned int pe_size,
> > + bool write_fault)
> > +{
> > + struct inode *inode = file_inode(vmf->vma->vm_file);
> > + vm_fault_t ret;
> > + pfn_t pfn;
> > +
> > + if (!IS_DAX(file_inode(vmf->vma->vm_file))) {
> > + pr_err("%s: file not marked IS_DAX!!\n", __func__);
> > + return VM_FAULT_SIGBUS;
> > + }
> > +
> > + if (write_fault) {
> > + sb_start_pagefault(inode->i_sb);
> > + file_update_time(vmf->vma->vm_file);
> > + }
> > +
> > + ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &famfs_iomap_ops);
> > + if (ret & VM_FAULT_NEEDDSYNC)
> > + ret = dax_finish_sync_fault(vmf, pe_size, pfn);
> > +
> > + if (write_fault)
> > + sb_end_pagefault(inode->i_sb);
> > +
> > + return ret;
> > +}
> > +
> > +static inline bool
> > +famfs_is_write_fault(struct vm_fault *vmf)
> > +{
> > + return (vmf->flags & FAULT_FLAG_WRITE) &&
> > + (vmf->vma->vm_flags & VM_SHARED);
> > +}
> > +
> > +static vm_fault_t
> > +famfs_filemap_fault(struct vm_fault *vmf)
> > +{
> > + return __famfs_fuse_filemap_fault(vmf, 0, famfs_is_write_fault(vmf));
> > +}
> > +
> > +static vm_fault_t
> > +famfs_filemap_huge_fault(struct vm_fault *vmf, unsigned int pe_size)
> > +{
> > + return __famfs_fuse_filemap_fault(vmf, pe_size, famfs_is_write_fault(vmf));
> > +}
> > +
> > +static vm_fault_t
> > +famfs_filemap_page_mkwrite(struct vm_fault *vmf)
> > +{
> > + return __famfs_fuse_filemap_fault(vmf, 0, true);
> > +}
> > +
> > +static vm_fault_t
> > +famfs_filemap_pfn_mkwrite(struct vm_fault *vmf)
> > +{
> > + return __famfs_fuse_filemap_fault(vmf, 0, true);
> > +}
> > +
> > +static vm_fault_t
> > +famfs_filemap_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff,
> > + pgoff_t end_pgoff)
> > +{
> > + return filemap_map_pages(vmf, start_pgoff, end_pgoff);
> > +}
> > +
> > +const struct vm_operations_struct famfs_file_vm_ops = {
> > + .fault = famfs_filemap_fault,
> > + .huge_fault = famfs_filemap_huge_fault,
> > + .map_pages = famfs_filemap_map_pages,
> > + .page_mkwrite = famfs_filemap_page_mkwrite,
> > + .pfn_mkwrite = famfs_filemap_pfn_mkwrite,
> > +};
> > +
> > +/*********************************************************************
> > + * file_operations
> > + */
> > +
> > +/**
> > + * famfs_file_bad() - Check for files that aren't in a valid state
> > + *
> > + * @inode - inode
> > + *
> > + * Returns: 0=success
> > + * -errno=failure
> > + */
> > +static ssize_t
> > +famfs_file_bad(struct inode *inode)
> > +{
> > + struct fuse_inode *fi = get_fuse_inode(inode);
> > + struct famfs_file_meta *meta = fi->famfs_meta;
> > + size_t i_size = i_size_read(inode);
> > +
> > + if (!meta) {
> > + pr_err("%s: un-initialized famfs file\n", __func__);
> > + return -EIO;
> > + }
> > + if (meta->error) {
> > + pr_debug("%s: previously detected metadata errors\n", __func__);
> > + return -EIO;
> > + }
> > + if (i_size != meta->file_size) {
> > + pr_warn("%s: i_size overwritten from %ld to %ld\n",
> > + __func__, meta->file_size, i_size);
> > + meta->error = true;
> > + return -ENXIO;
> > + }
> > + if (!IS_DAX(inode)) {
> > + pr_debug("%s: inode %llx IS_DAX is false\n", __func__, (u64)inode);
> > + return -ENXIO;
> > + }
> > + return 0;
> > +}
> > +
> > +static ssize_t
> > +famfs_fuse_rw_prep(struct kiocb *iocb, struct iov_iter *ubuf)
> > +{
> > + struct inode *inode = iocb->ki_filp->f_mapping->host;
> > + size_t i_size = i_size_read(inode);
> > + size_t count = iov_iter_count(ubuf);
> > + size_t max_count;
> > + ssize_t rc;
> > +
> > + rc = famfs_file_bad(inode);
> > + if (rc)
> > + return rc;
> > +
> > + max_count = max_t(size_t, 0, i_size - iocb->ki_pos);
> > +
> > + if (count > max_count)
> > + iov_iter_truncate(ubuf, max_count);
> > +
> > + if (!iov_iter_count(ubuf))
> > + return 0;
> > +
> > + return rc;
> > +}
> > +
> > +ssize_t
> > +famfs_fuse_read_iter(struct kiocb *iocb, struct iov_iter *to)
> > +{
> > + ssize_t rc;
> > +
> > + rc = famfs_fuse_rw_prep(iocb, to);
> > + if (rc)
> > + return rc;
> > +
> > + if (!iov_iter_count(to))
> > + return 0;
> > +
> > + rc = dax_iomap_rw(iocb, to, &famfs_iomap_ops);
> > +
> > + file_accessed(iocb->ki_filp);
> > + return rc;
> > +}
> > +
> > +ssize_t
> > +famfs_fuse_write_iter(struct kiocb *iocb, struct iov_iter *from)
> > +{
> > + ssize_t rc;
> > +
> > + rc = famfs_fuse_rw_prep(iocb, from);
> > + if (rc)
> > + return rc;
> > +
> > + if (!iov_iter_count(from))
> > + return 0;
> > +
> > + return dax_iomap_rw(iocb, from, &famfs_iomap_ops);
> > +}
> > +
> > +int
> > +famfs_fuse_mmap(struct file *file, struct vm_area_struct *vma)
> > +{
> > + struct inode *inode = file_inode(file);
> > + ssize_t rc;
> > +
> > + rc = famfs_file_bad(inode);
> > + if (rc)
> > + return (int)rc;
> > +
> > + file_accessed(file);
> > + vma->vm_ops = &famfs_file_vm_ops;
> > + vm_flags_set(vma, VM_HUGEPAGE);
> > + return 0;
> > +}
> > diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> > index 5d205eadb48f..24a14b176510 100644
> > --- a/fs/fuse/file.c
> > +++ b/fs/fuse/file.c
> > @@ -1874,6 +1874,8 @@ static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
> >
> > if (FUSE_IS_VIRTIO_DAX(fi))
> > return fuse_dax_read_iter(iocb, to);
> > + if (fuse_file_famfs(fi))
> > + return famfs_fuse_read_iter(iocb, to);
> >
> > /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> > if (ff->open_flags & FOPEN_DIRECT_IO)
> > @@ -1896,6 +1898,8 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> >
> > if (FUSE_IS_VIRTIO_DAX(fi))
> > return fuse_dax_write_iter(iocb, from);
> > + if (fuse_file_famfs(fi))
> > + return famfs_fuse_write_iter(iocb, from);
> >
> > /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> > if (ff->open_flags & FOPEN_DIRECT_IO)
> > @@ -1911,10 +1915,14 @@ static ssize_t fuse_splice_read(struct file *in, loff_t *ppos,
> > unsigned int flags)
> > {
> > struct fuse_file *ff = in->private_data;
> > + struct inode *inode = file_inode(in);
> > + struct fuse_inode *fi = get_fuse_inode(inode);
> >
> > /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> > if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
> > return fuse_passthrough_splice_read(in, ppos, pipe, len, flags);
> > + else if (fuse_file_famfs(fi))
> > + return -EIO; /* direct I/O doesn't make sense in dax_iomap */
> > else
> > return filemap_splice_read(in, ppos, pipe, len, flags);
> > }
> > @@ -1923,10 +1931,14 @@ static ssize_t fuse_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 inode *inode = file_inode(out);
> > + struct fuse_inode *fi = get_fuse_inode(inode);
> >
> > /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
> > if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
> > return fuse_passthrough_splice_write(pipe, out, ppos, len, flags);
> > + else if (fuse_file_famfs(fi))
> > + return -EIO; /* direct I/O doesn't make sense in dax_iomap */
> > else
> > return iter_file_splice_write(pipe, out, ppos, len, flags);
> > }
>
> This looks odd.
>
> Usually, the methods first check for FUSE_IS_VIRTIO_DAX() and
> fuse_file_famfs() to get this condition out of the way so I never needed
> to think about whether or not the code verifies that fuse_file_passthrough()
> and fuse_file_famfs() cannot co-exist.
>
> Is there a reason why you did not follow the same pattern here?
I think I just got a little sloppy. I'll do the famfs test first. Unless we
can rule out this path for famfs. But unlike virtiofs, famfs doesn't have
separate file_operations, so I suppose it must be checked.
>
> Also, your comment makes no sense.
> splice is not the case of direct I/O - quite the contrary.
Sorry, brain fart on the comment. Splice doesn't make sense for famfs because
famfs doesn't use the page cache. Will fix the comment too.
>
> Thanks,
> Amir.
Thank you Amir!
John
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