Request Handlers¶
(You can use the Index to directly jump to a specific handler).
-
class
llfuse.
Operations
¶ This class defines the general and request handler methods that an Python-LLFUSE file system may implement. If a particular request handler has not been implemented, it must raise
FUSEError
with an errorcode oferrno.ENOSYS
. Further requests of this type will then be handled directly by the FUSE kernel module without calling the handler again.It is recommended that file systems are derived from this class and only overwrite the handlers that they actually implement. (The default implementations defined in this class all just raise the not-implemented exception).
The only exception that request handlers are allowed to raise is
FUSEError
. This will cause the specified errno to be returned by the syscall that is being handled.Note that all character data (directory entry names, extended attribute names and values, symbolic link targets etc) are passed as
bytes
and must be returned asbytes
. This applies to both running under Python 2.x and 3.x-
access
(inode, mode, ctx)¶ Check if requesting process has mode rights on inode.
ctx will be a
RequestContext
instance. The method must return a boolean value.If the
default_permissions
mount option is given, this method is not called.
-
create
(inode_parent, name, mode, flags, ctx)¶ Create a file with permissions mode and open it with flags
ctx will be a
RequestContext
instance.The method must return a tuple of the form (fh, attr), where fh is a file handle like the one returned by
open
and attr is anEntryAttributes
instance with the attributes of the newly created directory entry.Once an inode has been returned by
lookup
,create
,symlink
,link
,mknod
ormkdir
, it must be kept by the file system until it receives aforget
request for the inode. Ifunlink
orrmdir
requests are received prior to theforget
call, they are expect to remove only the directory entry for the inode and defer removal of the inode itself until theforget
call.
-
destroy
()¶ Clean up operations.
This method will be called when
llfuse.close
has been called and the file system is about to be unmounted.Since this handler is thus not run as part of the main loop, it is also not called with the global lock acquired (unless the caller of
llfuse.close
already holds the lock).This method must not raise any exceptions (including
FUSEError
, since this method is not handling a particular syscall).
-
flush
(fh)¶ Handle close() syscall.
This method is called whenever a file descriptor is closed. It may be called multiple times for the same open file (e.g. if the file handle has been duplicated).
If the file system implements locking, this method must clear all locks belonging to the file handle’s owner.
-
forget
(inode_list)¶ Notify about inodes being removed from the kernel cache
inode_list is a list of
(inode, nlookup)
tuples. This method is called when the kernel removes the listed inodes from its internal caches. nlookup is the number of times that the inode has been looked up by calling either of thelookup
,create
,symlink
,mknod
,link
ormkdir
methods.The file system is expected to keep track of the number of times an inode has been looked up and forgotten. No request handlers other than
lookup
will be called for an inode with a lookup count of zero.If the lookup count reaches zero after a call to
forget
, the file system is expected to check if there are still directory entries referring to this inode and, if not, delete the inode itself.If the file system is unmounted, it will may not receive
forget
calls for inodes that are still cached. Thedestroy
method may be used to clean up any remaining inodes for which noforget
call has been received.
-
fsync
(fh, datasync)¶ Flush buffers for open file fh
If datasync is true, only the file contents should be flushed (in contrast to the metadata about the file).
-
fsyncdir
(fh, datasync)¶ Flush buffers for open directory fh
If datasync is true, only the directory contents should be flushed (in contrast to metadata about the directory itself).
-
getattr
(inode)¶ Get attributes for inode
This method should return an
EntryAttributes
instance with the attributes of inode. Theentry_timeout
attribute is ignored in this context.
-
getxattr
(inode, name)¶ Return extended attribute value
If the attribute does not exist, the method must raise
FUSEError
with an error code ofENOATTR
.
-
init
()¶ Initialize operations
This function will be called just before the file system starts handling requests. It must not raise any exceptions (including
FUSEError
, since this method is not handling a particular syscall).
-
link
(inode, new_parent_inode, new_name)¶ Create a hard link.
The method must return an
EntryAttributes
instance with the attributes of the newly created directory entry.Once an inode has been returned by
lookup
,create
,symlink
,link
,mknod
ormkdir
, it must be kept by the file system until it receives aforget
request for the inode. Ifunlink
orrmdir
requests are received prior to theforget
call, they are expect to remove only the directory entry for the inode and defer removal of the inode itself until theforget
call.
-
listxattr
(inode)¶ Get list of extended attribute names
-
lookup
(parent_inode, name)¶ Look up a directory entry by name and get its attributes.
If the entry name does not exist in the directory with inode parent_inode, this method must raise
FUSEError
with an errno oferrno.ENOENT
. Otherwise it must return anEntryAttributes
instance.Once an inode has been returned by
lookup
,create
,symlink
,link
,mknod
ormkdir
, it must be kept by the file system until it receives aforget
request for the inode. Ifunlink
orrmdir
requests are received prior to theforget
call, they are expect to remove only the directory entry for the inode and defer removal of the inode itself until theforget
call.The file system must be able to handle lookups for
.
and..
, no matter if these entries are returned byreaddir
or not.
-
mkdir
(parent_inode, name, mode, ctx)¶ Create a directory
ctx will be a
RequestContext
instance. The method must return anEntryAttributes
instance with the attributes of the newly created directory entry.Once an inode has been returned by
lookup
,create
,symlink
,link
,mknod
ormkdir
, it must be kept by the file system until it receives aforget
request for the inode. Ifunlink
orrmdir
requests are received prior to theforget
call, they are expect to remove only the directory entry for the inode and defer removal of the inode itself until theforget
call.
-
mknod
(parent_inode, name, mode, rdev, ctx)¶ Create (possibly special) file
ctx will be a
RequestContext
instance. The method must return anEntryAttributes
instance with the attributes of the newly created directory entry.Once an inode has been returned by
lookup
,create
,symlink
,link
,mknod
ormkdir
, it must be kept by the file system until it receives aforget
request for the inode. Ifunlink
orrmdir
requests are received prior to theforget
call, they are expect to remove only the directory entry for the inode and defer removal of the inode itself until theforget
call.
-
open
(inode, flags)¶ Open a file.
flags will be a bitwise or of the open flags described in the open(2) manpage and defined in the
os
module (with the exception ofO_CREAT
,O_EXCL
,O_NOCTTY
andO_TRUNC
)This method should return an integer file handle. The file handle will be passed to the
read
,write
,flush
,fsync
andrelease
methods to identify the open file.
-
opendir
(inode)¶ Open a directory.
This method should return an integer file handle. The file handle will be passed to the
readdir
,fsyncdir
andreleasedir
methods to identify the directory.
-
read
(fh, off, size)¶ Read size bytes from fh at position off
This function should return exactly the number of bytes requested except on EOF or error, otherwise the rest of the data will be substituted with zeroes.
-
readdir
(fh, off)¶ Read directory entries
This method should return an iterator over the contents of directory fh, starting at the entry identified by off. Directory entries must be of type
bytes
.The iterator must yield tuples of the form
(name, attr, next_)
, where attr is anEntryAttributes
instance and next_ gives an offset that can be passed as off to start a successivereaddir
call at the right position.Iteration may be stopped as soon as enough elements have been retrieved. The method should be prepared for this case.
If entries are added or removed during a
readdir
cycle, they may or may not be returned. However, they must not cause other entries to be skipped or returned more than once..
and..
entries may be included but are not required.
-
release
(fh)¶ Release open file
This method will be called when the last file descriptor of fh has been closed. Therefore it will be called exactly once for each
open
call.
-
releasedir
(fh)¶ Release open directory
This method must be called exactly once for each
opendir
call.
-
removexattr
(inode, name)¶ Remove extended attribute
If the attribute does not exist, the method must raise
FUSEError
with an error code ofENOATTR
.
-
rename
(inode_parent_old, name_old, inode_parent_new, name_new)¶ Rename a directory entry
If name_new already exists, it should be overwritten.
If the file system has received a
lookup
, but noforget
call for the file that is about to be overwritten,rename
is expected to only overwrite the directory entry and defer removal of the old inode with the its contents and metadata until theforget
call is received.
-
rmdir
(inode_parent, name)¶ Remove a directory
If the file system has received a
lookup
, but noforget
call for this file yet,unlink
is expected to remove only the directory entry and defer removal of the inode with the actual file contents and metadata until theforget
call is received.
-
setattr
(inode, attr)¶ Change attributes of inode
attr is an
EntryAttributes
instance with the new attributes. Only the attributesst_size
,st_mode
,st_uid
,st_gid
,st_atime
andst_mtime
are relevant. Unchanged attributes will have a valueNone
.The method should return a new
EntryAttributes
instance with the updated attributes (i.e., all attributes except forentry_timeout
should be set).
-
setxattr
(inode, name, value)¶ Set an extended attribute.
The attribute may or may not exist already.
-
stacktrace
()¶ Asynchronous debugging
This method will be called when the
fuse_stacktrace
extended attribute is set on the mountpoint. It will be called without holding the global lock. The default implementation logs the current stack trace of every running Python thread. This can be quite useful to debug file system deadlocks.
-
statfs
()¶ Get file system statistics
The method is expected to return an appropriately filled
StatvfsData
instance.
-
symlink
(inode_parent, name, target, ctx)¶ Create a symbolic link
ctx will be a
RequestContext
instance. The method must return anEntryAttributes
instance with the attributes of the newly created directory entry.Once an inode has been returned by
lookup
,create
,symlink
,link
,mknod
ormkdir
, it must be kept by the file system until it receives aforget
request for the inode. Ifunlink
orrmdir
requests are received prior to theforget
call, they are expect to remove only the directory entry for the inode and defer removal of the inode itself until theforget
call.
-
unlink
(parent_inode, name)¶ Remove a (possibly special) file
If the file system has received a
lookup
, but noforget
call for this file yet,unlink
is expected to remove only the directory entry and defer removal of the inode with the actual file contents and metadata until theforget
call is received.Note that an unlinked file may also appear again if it gets a new directory entry by the
link
method.
-
write
(fh, off, buf)¶ Write buf into fh at off
This method should return the number of bytes written. If no error occured, this should be exactly
len(buf)
.
-