Describe the write-once usage model, the strict in-place mmap and what
MAP_XIP_STRICT is for, extent pinning, manual defragmentation and how to read
its result, the power-loss ordering, the on-media layout, and the
limitations.
The NXFLAT page said ROMFS was the only file system able to serve the XIP
mappings its loader needs. That is now one of two, so point at both, and at
what the writable one adds: a module can arrive at run time instead of being
baked into a host-built image.
Assisted-by: Claude Code:claude-opus-5
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
FIOC_REFORMAT, FIOC_OPTIMIZE, FIOC_INTEGRITY and FIOC_DUMP act on a volume,
not on any one file, but the only route into a file system has been the
per-file ioctl method. A caller therefore has to open an unrelated file
just to name the volume it means.
For nxffs that is not merely awkward, it is a dead end. nxffs_ioctl()
refuses FIOC_REFORMAT while any file on the volume is open:
if (volume->ofiles)
{
ferr("ERROR: Open files\n");
ret = -EBUSY;
and every open file is on that list (nxffs_open.c). The descriptor used to
issue the command is itself such a file, so the check can never pass and
FIOC_REFORMAT is unreachable through the only interface that exposes it.
Add an optional ioctldir method to struct mountpt_operations, reached by
issuing the ioctl on a descriptor for the mountpoint directory:
fd = open("/mnt/nxffs", O_RDONLY | O_DIRECTORY);
ioctl(fd, FIOC_REFORMAT, 0);
It takes the same (mountpt, dir) pair as opendir/readdir/rewinddir, so it
reads as a member of the directory-operations family; the file system
recovers the volume from the mountpoint inode and may ignore dir. The
member is placed at the end of the structure rather than beside the other
directory operations on purpose: every file system initialises
mountpt_operations positionally, so a member inserted mid-structure would
force all of them to add a slot for a method they do not implement.
Appending keeps the change to one file system.
dir_ioctl() gives that method the first chance at every command when the
directory belongs to a mounted volume and the file system provides one, and
falls back to its own handling of FIOC_FILEPATH and BIOC_FLUSH when the file
system answers -ENOTTY. Trying the file system first is what lets a file
system override a command the VFS would otherwise answer generically; the
-ENOTTY fallback is what keeps the generic answers available to everyone
else. A file system that leaves the method NULL is unaffected: the VFS
answers exactly as before.
The existing per-file method could not simply be reused for this. It takes
a struct file, and every implementation that has an ioctl -- fat, romfs,
tmpfs, spiffs among them -- asserts on filep->f_priv and dereferences it,
so handing it a directory descriptor with no open file behind it would
fault. Making the entry point separate keeps that contract intact and
makes support explicit rather than assumed.
nxffs implements it, which is what makes its FIOC_REFORMAT reachable. The
per-file path is left in place and both share one implementation, so
nothing that works today stops working. spiffs, which has the same shape
of volume commands, can follow.
Measured on sim:nxffs, with one file written to the volume and then the
same sequence of ioctls issued on a file descriptor, on a descriptor for the
mountpoint directory, and on a descriptor for a pseudo file system directory.
Before:
FIOC_REFORMAT via file fd: ret=-1 errno=16 (EBUSY, as expected)
FIOC_REFORMAT via dir fd: ret=-1 errno=25
FIOC_FILEPATH via dir fd: ret=0 "/mnt/nxffs//"
BIOC_FLUSH via dir fd: ret=0
bogus cmd via dir fd: ret=-1 errno=25
FIOC_FILEPATH via /dev fd: ret=0 "/dev//"
bogus cmd via /dev fd: ret=-1 errno=25
name still in the raw MTD image afterwards: yes
After:
FIOC_REFORMAT via file fd: ret=-1 errno=16 (EBUSY, as expected)
FIOC_REFORMAT via dir fd: ret=0
FIOC_FILEPATH via dir fd: ret=0 "/mnt/nxffs//"
BIOC_FLUSH via dir fd: ret=0
bogus cmd via dir fd: ret=-1 errno=25
FIOC_FILEPATH via /dev fd: ret=0 "/dev//"
bogus cmd via /dev fd: ret=-1 errno=25
name still in the raw MTD image afterwards: no
Only the FIOC_REFORMAT line on the directory descriptor changes, and the raw
MTD image confirms the volume really was erased. FIOC_FILEPATH and
BIOC_FLUSH on a directory still answer even though nxffs is now consulted
ahead of them, an unrecognised command is still refused rather than
forwarded blindly, and a directory in the pseudo file system, which has no
ioctldir at all, is untouched.
Assisted-by: Claude Code:claude-opus-4-8
Assisted-by: Claude Code:claude-fable-5
Assisted-by: Claude Code:claude-opus-5
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
Check open access against file mode and owner via fs_checkmode(), verify
parent directory permissions on create, and assign creator uid/gid to
newly created files.
Signed-off-by: Abhishek Mishra <mishra.abhishek2808@gmail.com>
This adds a kernel-level performance profiler for the VFS.
By enabling CONFIG_FS_PROFILER, the core VFS system calls
(file_read, file_write, file_open, and file_close) are
instrumented to track high-resolution execution times using
clock_systime_timespec() seamlessly.
The collected statistics are exposed dynamically via a new
procfs node at /proc/fs/profile, allowing CI regression
testing without needing external debugging tools.
Signed-off-by: Sumit6307 <sumitkesar6307@gmail.com>
Fix 269 occurrences of duplicate "the" word typo found in 209 files
across source code, header files, and configuration.
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
Describes some of the quirks of using littlefs on NuttX and links to an
issue discussing the sync semantics.
Signed-off-by: Matteo Golin <matteo.golin@gmail.com>
IN_CLOSE_WRITE and IN_CLOSE_NOWRITE are now supported and IN_MODIFY
can be used for truncate as well.
Signed-off-by: Michal Lenc <michallenc@seznam.cz>
This adds initial document for using TMPFS based on my short experience,
hoping to save people's time on guessing how to use.
Signed-off-by: Yanfeng Liu <yfliu2008@qq.com>
