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Commit 2ece3e8c authored by Aaron Jacobs's avatar Aaron Jacobs
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Deleted the FileSystem interface.

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// Copyright 2015 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package fuse
import (
"fmt"
"os"
"time"
"github.com/jacobsa/bazilfuse"
"golang.org/x/net/context"
)
// An interface that must be implemented by file systems to be mounted with
// FUSE. See also the comments on request and response structs.
//
// Not all methods need to have interesting implementations. Embed a field of
// type fuseutil.NotImplementedFileSystem to inherit defaults that return
// ENOSYS to the kernel.
//
// Must be safe for concurrent access via all methods.
type FileSystem interface {
// This method is called once when mounting the file system. It must succeed
// in order for the mount to succeed.
Init(
ctx context.Context,
req *InitRequest) (*InitResponse, error)
///////////////////////////////////
// Inodes
///////////////////////////////////
// Look up a child by name within a parent directory. The kernel calls this
// when resolving user paths to dentry structs, which are then cached.
LookUpInode(
ctx context.Context,
req *LookUpInodeRequest) (*LookUpInodeResponse, error)
// Refresh the attributes for an inode whose ID was previously returned by
// LookUpInode. The kernel calls this when the FUSE VFS layer's cache of
// inode attributes is stale. This is controlled by the AttributesExpiration
// field of responses to LookUp, etc.
GetInodeAttributes(
ctx context.Context,
req *GetInodeAttributesRequest) (*GetInodeAttributesResponse, error)
// Change attributes for an inode.
//
// The kernel calls this for obvious cases like chmod(2), and for less
// obvious cases like ftrunctate(2).
SetInodeAttributes(
ctx context.Context,
req *SetInodeAttributesRequest) (*SetInodeAttributesResponse, error)
// Forget an inode ID previously issued (e.g. by LookUpInode or MkDir). The
// kernel calls this when removing an inode from its internal caches.
ForgetInode(
ctx context.Context,
req *ForgetInodeRequest) (*ForgetInodeResponse, error)
///////////////////////////////////
// Inode creation
///////////////////////////////////
// Create a directory inode as a child of an existing directory inode. The
// kernel sends this in response to a mkdir(2) call.
//
// The kernel appears to verify the name doesn't already exist (mkdir calls
// mkdirat calls user_path_create calls filename_create, which verifies:
// http://goo.gl/FZpLu5). But volatile file systems and paranoid non-volatile
// file systems should check for the reasons described below on CreateFile.
MkDir(
ctx context.Context,
req *MkDirRequest) (*MkDirResponse, error)
// Create a file inode and open it.
//
// The kernel calls this method when the user asks to open a file with the
// O_CREAT flag and the kernel has observed that the file doesn't exist. (See
// for example lookup_open, http://goo.gl/PlqE9d).
//
// However it's impossible to tell for sure that all kernels make this check
// in all cases and the official fuse documentation is less than encouraging
// (" the file does not exist, first create it with the specified mode, and
// then open it"). Therefore file systems would be smart to be paranoid and
// check themselves, returning EEXIST when the file already exists. This of
// course particularly applies to file systems that are volatile from the
// kernel's point of view.
CreateFile(
ctx context.Context,
req *CreateFileRequest) (*CreateFileResponse, error)
///////////////////////////////////
// Inode destruction
///////////////////////////////////
// Unlink a directory from its parent. Because directories cannot have a link
// count above one, this means the directory inode should be deleted as well
// once the kernel calls ForgetInode.
//
// The file system is responsible for checking that the directory is empty.
//
// Sample implementation in ext2: ext2_rmdir (http://goo.gl/B9QmFf)
RmDir(
ctx context.Context,
req *RmDirRequest) (*RmDirResponse, error)
// Unlink a file from its parent. If this brings the inode's link count to
// zero, the inode should be deleted once the kernel calls ForgetInode. It
// may still be referenced before then if a user still has the file open.
//
// Sample implementation in ext2: ext2_unlink (http://goo.gl/hY6r6C)
Unlink(
ctx context.Context,
req *UnlinkRequest) (*UnlinkResponse, error)
///////////////////////////////////
// Directory handles
///////////////////////////////////
// Open a directory inode.
//
// On Linux the kernel calls this method when setting up a struct file for a
// particular inode with type directory, usually in response to an open(2)
// call from a user-space process. On OS X it may not be called for every
// open(2) (cf. https://github.com/osxfuse/osxfuse/issues/199).
OpenDir(
ctx context.Context,
req *OpenDirRequest) (*OpenDirResponse, error)
// Read entries from a directory previously opened with OpenDir.
ReadDir(
ctx context.Context,
req *ReadDirRequest) (*ReadDirResponse, error)
// Release a previously-minted directory handle. The kernel calls this when
// there are no more references to an open directory: all file descriptors
// are closed and all memory mappings are unmapped.
//
// The kernel guarantees that the handle ID will not be used in further calls
// to the file system (unless it is reissued by the file system).
ReleaseDirHandle(
ctx context.Context,
req *ReleaseDirHandleRequest) (*ReleaseDirHandleResponse, error)
///////////////////////////////////
// File handles
///////////////////////////////////
// Open a file inode.
//
// On Linux the kernel calls this method when setting up a struct file for a
// particular inode with type file, usually in response to an open(2) call
// from a user-space process. On OS X it may not be called for every open(2)
// (cf.https://github.com/osxfuse/osxfuse/issues/199).
OpenFile(
ctx context.Context,
req *OpenFileRequest) (*OpenFileResponse, error)
// Read data from a file previously opened with CreateFile or OpenFile.
//
// Note that this method is not called for every call to read(2) by the end
// user; some reads may be served by the page cache. See notes on Write for
// more.
ReadFile(
ctx context.Context,
req *ReadFileRequest) (*ReadFileResponse, error)
// Write data to a file previously opened with CreateFile or OpenFile.
//
// When the user writes data using write(2), the write goes into the page
// cache and the page is marked dirty. Later the kernel may write back the
// page via the FUSE VFS layer, causing this method to be called:
//
// * The kernel calls address_space_operations::writepage when a dirty page
// needs to be written to backing store (cf. http://goo.gl/Ezbewg). Fuse
// sets this to fuse_writepage (cf. http://goo.gl/IeNvLT).
//
// * (http://goo.gl/Eestuy) fuse_writepage calls fuse_writepage_locked.
//
// * (http://goo.gl/RqYIxY) fuse_writepage_locked makes a write request to
// the userspace server.
//
// Note that writes *will* be received before a call to Flush when closing
// the file descriptor to which they were written:
//
// * (http://goo.gl/PheZjf) fuse_flush calls write_inode_now, which appears
// to start a writeback in the background (it talks about a "flusher
// thread").
//
// * (http://goo.gl/1IiepM) fuse_flush then calls fuse_sync_writes, which
// "[waits] for all pending writepages on the inode to finish".
//
// * (http://goo.gl/zzvxWv) Only then does fuse_flush finally send the
// flush request.
//
WriteFile(
ctx context.Context,
req *WriteFileRequest) (*WriteFileResponse, error)
// Synchronize the current contents of an open file to storage.
//
// vfs.txt documents this as being called for by the fsync(2) system call
// (cf. http://goo.gl/j9X8nB). Code walk for that case:
//
// * (http://goo.gl/IQkWZa) sys_fsync calls do_fsync, calls vfs_fsync, calls
// vfs_fsync_range.
//
// * (http://goo.gl/5L2SMy) vfs_fsync_range calls f_op->fsync.
//
// Note that this is also called by fdatasync(2) (cf. http://goo.gl/01R7rF),
// and may be called for msync(2) with the MS_SYNC flag (see the notes on
// FlushFile).
//
// See also: FlushFile, which may perform a similar purpose when closing a
// file (but which is not used in "real" file systems).
SyncFile(
ctx context.Context,
req *SyncFileRequest) (*SyncFileResponse, error)
// Flush the current state of an open file to storage upon closing a file
// descriptor.
//
// vfs.txt documents this as being called for each close(2) system call (cf.
// http://goo.gl/FSkbrq). Code walk for that case:
//
// * (http://goo.gl/e3lv0e) sys_close calls __close_fd, calls filp_close.
// * (http://goo.gl/nI8fxD) filp_close calls f_op->flush (fuse_flush).
//
// But note that this is also called in other contexts where a file
// descriptor is closed, such as dup2(2) (cf. http://goo.gl/NQDvFS). In the
// case of close(2), a flush error is returned to the user. For dup2(2), it
// is not.
//
// One potentially significant case where this may not be called is mmap'd
// files, where the behavior is complicated:
//
// * munmap(2) does not cause flushes (cf. http://goo.gl/j8B9g0).
//
// * On OS X, if a user modifies a mapped file via the mapping before
// closing the file with close(2), the WriteFile calls for the
// modifications may not be received before the FlushFile request for the
// close(2) (cf. http://goo.gl/kVmNcx).
//
// * However, even on OS X you can arrange for writes via a mapping to be
// flushed by calling msync(2) followed by close(2). On OS X msync(2)
// will cause a WriteFile to go through and close(2) will cause a
// FlushFile as usual (cf. http://goo.gl/kVmNcx). On Linux, msync(2) does
// nothing unless you set the MS_SYNC flag, in which case it causes a
// SyncFile (cf. http://goo.gl/P3mErk).
//
// In summary: if you make data durable in both FlushFile and SyncFile, then
// your users can get safe behavior from mapped files by calling msync(2)
// with MS_SYNC, followed by munmap(2), followed by close(2). On Linux, the
// msync(2) appears to be optional because close(2) implies dirty page
// writeback (cf. http://goo.gl/HyzLTT).
//
// Because of cases like dup2(2), calls to FlushFile are not necessarily one
// to one with calls to OpenFile. They should not be used for reference
// counting, and the handle must remain valid even after the method is called
// (use ReleaseFileHandle to dispose of it).
//
// Typical "real" file systems do not implement this, presumably relying on
// the kernel to write out the page cache to the block device eventually.
// They can get away with this because a later open(2) will see the same
// data. A file system that writes to remote storage however probably wants
// to at least schedule a real flush, and maybe do it immediately in order to
// return any errors that occur.
FlushFile(
ctx context.Context,
req *FlushFileRequest) (*FlushFileResponse, error)
// Release a previously-minted file handle. The kernel calls this when there
// are no more references to an open file: all file descriptors are closed
// and all memory mappings are unmapped.
//
// The kernel guarantees that the handle ID will not be used in further calls
// to the file system (unless it is reissued by the file system).
ReleaseFileHandle(
ctx context.Context,
req *ReleaseFileHandleRequest) (*ReleaseFileHandleResponse, error)
}
////////////////////////////////////////////////////////////////////////
// Simple types
////////////////////////////////////////////////////////////////////////
// A 64-bit number used to uniquely identify a file or directory in the file
// system. File systems may mint inode IDs with any value except for
// RootInodeID.
//
// This corresponds to struct inode::i_no in the VFS layer.
// (Cf. http://goo.gl/tvYyQt)
type InodeID uint64
// A distinguished inode ID that identifies the root of the file system, e.g.
// in a request to OpenDir or LookUpInode. Unlike all other inode IDs, which
// are minted by the file system, the FUSE VFS layer may send a request for
// this ID without the file system ever having referenced it in a previous
// response.
const RootInodeID = 1
func init() {
// Make sure the constant above is correct. We do this at runtime rather than
// defining the constant in terms of bazilfuse.RootID for two reasons:
//
// 1. Users can more clearly see that the root ID is low and can therefore
// be used as e.g. an array index, with space reserved up to the root.
//
// 2. The constant can be untyped and can therefore more easily be used as
// an array index.
//
if RootInodeID != bazilfuse.RootID {
panic(
fmt.Sprintf(
"Oops, RootInodeID is wrong: %v vs. %v",
RootInodeID,
bazilfuse.RootID))
}
}
// Attributes for a file or directory inode. Corresponds to struct inode (cf.
// http://goo.gl/tvYyQt).
type InodeAttributes struct {
Size uint64
// The number of incoming hard links to this inode.
Nlink uint64
// The mode of the inode. This is exposed to the user in e.g. the result of
// fstat(2).
//
// Note that in contrast to the defaults for FUSE, this package mounts file
// systems in a manner such that the kernel checks inode permissions in the
// standard posix way. This is implemented by setting the default_permissions
// mount option (cf. http://goo.gl/1LxOop and http://goo.gl/1pTjuk).
//
// For example, in the case of mkdir:
//
// * (http://goo.gl/JkdxDI) sys_mkdirat calls inode_permission.
//
// * (...) inode_permission eventually calls do_inode_permission.
//
// * (http://goo.gl/aGCsmZ) calls i_op->permission, which is
// fuse_permission (cf. http://goo.gl/VZ9beH).
//
// * (http://goo.gl/5kqUKO) fuse_permission doesn't do anything at all for
// several code paths if FUSE_DEFAULT_PERMISSIONS is unset. In contrast,
// if that flag *is* set, then it calls generic_permission.
//
Mode os.FileMode
// Time information. See `man 2 stat` for full details.
Atime time.Time // Time of last access
Mtime time.Time // Time of last modification
Ctime time.Time // Time of last modification to inode
Crtime time.Time // Time of creation (OS X only)
// Ownership information
Uid uint32
Gid uint32
}
// A generation number for an inode. Irrelevant for file systems that won't be
// exported over NFS. For those that will and that reuse inode IDs when they
// become free, the generation number must change when an ID is reused.
//
// This corresponds to struct inode::i_generation in the VFS layer.
// (Cf. http://goo.gl/tvYyQt)
//
// Some related reading:
//
// http://fuse.sourceforge.net/doxygen/structfuse__entry__param.html
// http://stackoverflow.com/q/11071996/1505451
// http://goo.gl/CqvwyX
// http://julipedia.meroh.net/2005/09/nfs-file-handles.html
// http://goo.gl/wvo3MB
//
type GenerationNumber uint64
// An opaque 64-bit number used to identify a particular open handle to a file
// or directory.
//
// This corresponds to fuse_file_info::fh.
type HandleID uint64
// An offset into an open directory handle. This is opaque to FUSE, and can be
// used for whatever purpose the file system desires. See notes on
// ReadDirRequest.Offset for details.
type DirOffset uint64
// A header that is included with every request.
type RequestHeader struct {
// Credentials information for the process making the request.
Uid uint32
Gid uint32
}
// Information about a child inode within its parent directory. Shared by the
// responses for LookUpInode, MkDir, CreateFile, etc. Consumed by the kernel in
// order to set up a dcache entry.
type ChildInodeEntry struct {
// The ID of the child inode. The file system must ensure that the returned
// inode ID remains valid until a later call to ForgetInode.
Child InodeID
// A generation number for this incarnation of the inode with the given ID.
// See comments on type GenerationNumber for more.
Generation GenerationNumber
// Current attributes for the child inode.
//
// When creating a new inode, the file system is responsible for initializing
// and recording (where supported) attributes like time information,
// ownership information, etc.
//
// Ownership information in particular must be set to something reasonable or
// by default root will own everything and unprivileged users won't be able
// to do anything useful. In traditional file systems in the kernel, the
// function inode_init_owner (http://goo.gl/5qavg8) contains the
// standards-compliant logic for this.
Attributes InodeAttributes
// The FUSE VFS layer in the kernel maintains a cache of file attributes,
// used whenever up to date information about size, mode, etc. is needed.
//
// For example, this is the abridged call chain for fstat(2):
//
// * (http://goo.gl/tKBH1p) fstat calls vfs_fstat.
// * (http://goo.gl/3HeITq) vfs_fstat eventuall calls vfs_getattr_nosec.
// * (http://goo.gl/DccFQr) vfs_getattr_nosec calls i_op->getattr.
// * (http://goo.gl/dpKkst) fuse_getattr calls fuse_update_attributes.
// * (http://goo.gl/yNlqPw) fuse_update_attributes uses the values in the
// struct inode if allowed, otherwise calling out to the user-space code.
//
// In addition to obvious cases like fstat, this is also used in more subtle
// cases like updating size information before seeking (http://goo.gl/2nnMFa)
// or reading (http://goo.gl/FQSWs8).
//
// Most 'real' file systems do not set inode_operations::getattr, and
// therefore vfs_getattr_nosec calls generic_fillattr which simply grabs the
// information from the inode struct. This makes sense because these file
// systems cannot spontaneously change; all modifications go through the
// kernel which can update the inode struct as appropriate.
//
// In contrast, a FUSE file system may have spontaneous changes, so it calls
// out to user space to fetch attributes. However this is expensive, so the
// FUSE layer in the kernel caches the attributes if requested.
//
// This field controls when the attributes returned in this response and
// stashed in the struct inode should be re-queried. Leave at the zero value
// to disable caching.
//
// More reading:
// http://stackoverflow.com/q/21540315/1505451
AttributesExpiration time.Time
// The time until which the kernel may maintain an entry for this name to
// inode mapping in its dentry cache. After this time, it will revalidate the
// dentry.
//
// As in the discussion of attribute caching above, unlike real file systems,
// FUSE file systems may spontaneously change their name -> inode mapping.
// Therefore the FUSE VFS layer uses dentry_operations::d_revalidate
// (http://goo.gl/dVea0h) to intercept lookups and revalidate by calling the
// user-space LookUpInode method. However the latter may be slow, so it
// caches the entries until the time defined by this field.
//
// Example code walk:
//
// * (http://goo.gl/M2G3tO) lookup_dcache calls d_revalidate if enabled.
// * (http://goo.gl/ef0Elu) fuse_dentry_revalidate just uses the dentry's
// inode if fuse_dentry_time(entry) hasn't passed. Otherwise it sends a
// lookup request.
//
// Leave at the zero value to disable caching.
//
// Beware: this value is ignored on OS X, where entry caching is disabled by
// default. See notes on MountConfig.EnableVnodeCaching for more.
EntryExpiration time.Time
}
////////////////////////////////////////////////////////////////////////
// Requests and responses
////////////////////////////////////////////////////////////////////////
type InitRequest struct {
Header RequestHeader
}
type InitResponse struct {
}
type LookUpInodeRequest struct {
Header RequestHeader
// The ID of the directory inode to which the child belongs.
Parent InodeID
// The name of the child of interest, relative to the parent. For example, in
// this directory structure:
//
// foo/
// bar/
// baz
//
// the file system may receive a request to look up the child named "bar" for
// the parent foo/.
Name string
}
type LookUpInodeResponse struct {
Entry ChildInodeEntry
}
type GetInodeAttributesRequest struct {
Header RequestHeader
// The inode of interest.
Inode InodeID
}
type GetInodeAttributesResponse struct {
// Attributes for the inode, and the time at which they should expire. See
// notes on ChildInodeEntry.AttributesExpiration for more.
Attributes InodeAttributes
AttributesExpiration time.Time
}
type SetInodeAttributesRequest struct {
Header RequestHeader
// The inode of interest.
Inode InodeID
// The attributes to modify, or nil for attributes that don't need a change.
Size *uint64
Mode *os.FileMode
Atime *time.Time
Mtime *time.Time
}
type SetInodeAttributesResponse struct {
// The new attributes for the inode, and the time at which they should
// expire. See notes on ChildInodeEntry.AttributesExpiration for more.
Attributes InodeAttributes
AttributesExpiration time.Time
}
type ForgetInodeRequest struct {
Header RequestHeader
// The inode to be forgotten. The kernel guarantees that the node ID will not
// be used in further calls to the file system (unless it is reissued by the
// file system).
ID InodeID
}
type ForgetInodeResponse struct {
}
type MkDirRequest struct {
Header RequestHeader
// The ID of parent directory inode within which to create the child.
Parent InodeID
// The name of the child to create, and the mode with which to create it.
Name string
Mode os.FileMode
}
type MkDirResponse struct {
// Information about the inode that was created.
Entry ChildInodeEntry
}
type CreateFileRequest struct {
Header RequestHeader
// The ID of parent directory inode within which to create the child file.
Parent InodeID
// The name of the child to create, and the mode with which to create it.
Name string
Mode os.FileMode
// Flags for the open operation.
Flags bazilfuse.OpenFlags
}
type CreateFileResponse struct {
// Information about the inode that was created.
Entry ChildInodeEntry
// An opaque ID that will be echoed in follow-up calls for this file using
// the same struct file in the kernel. In practice this usually means
// follow-up calls using the file descriptor returned by open(2).
//
// The handle may be supplied in future calls to methods like ReadFile that
// accept a file handle. The file system must ensure this ID remains valid
// until a later call to ReleaseFileHandle.
Handle HandleID
}
type RmDirRequest struct {
Header RequestHeader
// The ID of parent directory inode, and the name of the directory being
// removed within it.
Parent InodeID
Name string
}
type UnlinkResponse struct {
}
type UnlinkRequest struct {
Header RequestHeader
// The ID of parent directory inode, and the name of the file being removed
// within it.
Parent InodeID
Name string
}
type RmDirResponse struct {
}
type OpenDirRequest struct {
Header RequestHeader
// The ID of the inode to be opened.
Inode InodeID
// Mode and options flags.
Flags bazilfuse.OpenFlags
}
type OpenDirResponse struct {
// An opaque ID that will be echoed in follow-up calls for this directory
// using the same struct file in the kernel. In practice this usually means
// follow-up calls using the file descriptor returned by open(2).
//
// The handle may be supplied in future calls to methods like ReadDir that
// accept a directory handle. The file system must ensure this ID remains
// valid until a later call to ReleaseDirHandle.
Handle HandleID
}
type ReadDirRequest struct {
Header RequestHeader
// The directory inode that we are reading, and the handle previously
// returned by OpenDir when opening that inode.
Inode InodeID
Handle HandleID
// The offset within the directory at which to read.
//
// Warning: this field is not necessarily a count of bytes. Its legal values
// are defined by the results returned in ReadDirResponse. See the notes
// below and the notes on that struct.
//
// In the Linux kernel this ultimately comes from file::f_pos, which starts
// at zero and is set by llseek and by the final consumed result returned by
// each call to ReadDir:
//
// * (http://goo.gl/2nWJPL) iterate_dir, which is called by getdents(2) and
// readdir(2), sets dir_context::pos to file::f_pos before calling
// f_op->iterate, and then does the opposite assignment afterward.
//
// * (http://goo.gl/rTQVSL) fuse_readdir, which implements iterate for fuse
// directories, passes dir_context::pos as the offset to fuse_read_fill,
// which passes it on to user-space. fuse_readdir later calls
// parse_dirfile with the same context.
//
// * (http://goo.gl/vU5ukv) For each returned result (except perhaps the
// last, which may be truncated by the page boundary), parse_dirfile
// updates dir_context::pos with fuse_dirent::off.
//
// It is affected by the Posix directory stream interfaces in the following
// manner:
//
// * (http://goo.gl/fQhbyn, http://goo.gl/ns1kDF) opendir initially causes
// filepos to be set to zero.
//
// * (http://goo.gl/ezNKyR, http://goo.gl/xOmDv0) readdir allows the user
// to iterate through the directory one entry at a time. As each entry is
// consumed, its d_off field is stored in __dirstream::filepos.
//
// * (http://goo.gl/WEOXG8, http://goo.gl/rjSXl3) telldir allows the user
// to obtain the d_off field from the most recently returned entry.
//
// * (http://goo.gl/WG3nDZ, http://goo.gl/Lp0U6W) seekdir allows the user
// to seek backward to an offset previously returned by telldir. It
// stores the new offset in filepos, and calls llseek to update the
// kernel's struct file.
//
// * (http://goo.gl/gONQhz, http://goo.gl/VlrQkc) rewinddir allows the user
// to go back to the beginning of the directory, obtaining a fresh view.
// It updates filepos and calls llseek to update the kernel's struct
// file.
//
// Unfortunately, FUSE offers no way to intercept seeks
// (http://goo.gl/H6gEXa), so there is no way to cause seekdir or rewinddir
// to fail. Additionally, there is no way to distinguish an explicit
// rewinddir followed by readdir from the initial readdir, or a rewinddir
// from a seekdir to the value returned by telldir just after opendir.
//
// Luckily, Posix is vague about what the user will see if they seek
// backwards, and requires the user not to seek to an old offset after a
// rewind. The only requirement on freshness is that rewinddir results in
// something that looks like a newly-opened directory. So FUSE file systems
// may e.g. cache an entire fresh listing for each ReadDir with a zero
// offset, and return array offsets into that cached listing.
Offset DirOffset
// The maximum number of bytes to return in ReadDirResponse.Data. A smaller
// number is acceptable.
Size int
}
type ReadDirResponse struct {
// A buffer consisting of a sequence of FUSE directory entries in the format
// generated by fuse_add_direntry (http://goo.gl/qCcHCV), which is consumed
// by parse_dirfile (http://goo.gl/2WUmD2). Use fuseutil.AppendDirent to
// generate this data.
//
// The buffer must not exceed the length specified in ReadDirRequest.Size. It
// is okay for the final entry to be truncated; parse_dirfile copes with this
// by ignoring the partial record.
//
// Each entry returned exposes a directory offset to the user that may later
// show up in ReadDirRequest.Offset. See notes on that field for more
// information.
//
// An empty buffer indicates the end of the directory has been reached.
Data []byte
}
type ReleaseDirHandleRequest struct {
Header RequestHeader
// The handle ID to be released. The kernel guarantees that this ID will not
// be used in further calls to the file system (unless it is reissued by the
// file system).
Handle HandleID
}
type ReleaseDirHandleResponse struct {
}
type OpenFileRequest struct {
Header RequestHeader
// The ID of the inode to be opened.
Inode InodeID
// Mode and options flags.
Flags bazilfuse.OpenFlags
}
type OpenFileResponse struct {
// An opaque ID that will be echoed in follow-up calls for this file using
// the same struct file in the kernel. In practice this usually means
// follow-up calls using the file descriptor returned by open(2).
//
// The handle may be supplied in future calls to methods like ReadFile that
// accept a file handle. The file system must ensure this ID remains valid
// until a later call to ReleaseFileHandle.
Handle HandleID
}
type ReadFileRequest struct {
Header RequestHeader
// The file inode that we are reading, and the handle previously returned by
// CreateFile or OpenFile when opening that inode.
Inode InodeID
Handle HandleID
// The range of the file to read.
//
// The FUSE documentation requires that exactly the number of bytes be
// returned, except in the case of EOF or error (http://goo.gl/ZgfBkF). This
// appears to be because it uses file mmapping machinery
// (http://goo.gl/SGxnaN) to read a page at a time. It appears to understand
// where EOF is by checking the inode size (http://goo.gl/0BkqKD), returned
// by a previous call to LookUpInode, GetInodeAttributes, etc.
Offset int64
Size int
}
type ReadFileResponse struct {
// The data read. If this is less than the requested size, it indicates EOF.
// An error should not be returned in this case.
Data []byte
}
type WriteFileRequest struct {
Header RequestHeader
// The file inode that we are modifying, and the handle previously returned
// by CreateFile or OpenFile when opening that inode.
Inode InodeID
Handle HandleID
// The offset at which to write the data below.
//
// The man page for pwrite(2) implies that aside from changing the file
// handle's offset, using pwrite is equivalent to using lseek(2) and then
// write(2). The man page for lseek(2) says the following:
//
// "The lseek() function allows the file offset to be set beyond the end of
// the file (but this does not change the size of the file). If data is later
// written at this point, subsequent reads of the data in the gap (a "hole")
// return null bytes (aq\0aq) until data is actually written into the gap."
//
// It is therefore reasonable to assume that the kernel is looking for
// the following semantics:
//
// * If the offset is less than or equal to the current size, extend the
// file as necessary to fit any data that goes past the end of the file.
//
// * If the offset is greater than the current size, extend the file
// with null bytes until it is not, then do the above.
//
Offset int64
// The data to write.
//
// The FUSE documentation requires that exactly the number of bytes supplied
// be written, except on error (http://goo.gl/KUpwwn). This appears to be
// because it uses file mmapping machinery (http://goo.gl/SGxnaN) to write a
// page at a time.
Data []byte
}
type WriteFileResponse struct {
}
type SyncFileRequest struct {
Header RequestHeader
// The file and handle being sync'd.
Inode InodeID
Handle HandleID
}
type SyncFileResponse struct {
}
type FlushFileRequest struct {
Header RequestHeader
// The file and handle being flushed.
Inode InodeID
Handle HandleID
}
type FlushFileResponse struct {
}
type ReleaseFileHandleRequest struct {
Header RequestHeader
// The handle ID to be released. The kernel guarantees that this ID will not
// be used in further calls to the file system (unless it is reissued by the
// file system).
Handle HandleID
}
type ReleaseFileHandleResponse struct {
}
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