From bdd01bd70e031accfd4acda1220e1f3d01a80924 Mon Sep 17 00:00:00 2001
From: Moritz Gmeiner <moritz@gmeiner.net>
Date: Sat, 2 Aug 2025 17:22:32 +0200
Subject: [PATCH] implemented setattr (properly)

---
 Cargo.lock               |   2 +
 fat-bits/Cargo.toml      |   1 +
 fat-bits/src/datetime.rs |  22 ++--
 fat-bits/src/dir.rs      | 142 +++++++++++-----------
 fat-fuse/Cargo.toml      |   1 +
 fat-fuse/src/fuse.rs     | 253 ++++++++++++++++++++++++++++-----------
 fat-fuse/src/inode.rs    | 130 +++++++++++++-------
 fat-fuse/src/lib.rs      |   4 +-
 8 files changed, 356 insertions(+), 199 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index f0d44bf..83fc35b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -238,6 +238,7 @@ dependencies = [
  "chrono",
  "compact_str",
  "enum_dispatch",
+ "log",
  "static_assertions",
  "thiserror 2.0.12",
 ]
@@ -255,6 +256,7 @@ name = "fat-fuse"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "bitflags",
  "chrono",
  "compact_string",
  "fat-bits",
diff --git a/fat-bits/Cargo.toml b/fat-bits/Cargo.toml
index 45ec5d4..6c53e1f 100644
--- a/fat-bits/Cargo.toml
+++ b/fat-bits/Cargo.toml
@@ -12,5 +12,6 @@ chrono = { version = "0.4.41", default-features = false, features = [
 ] }
 compact_str = "0.9.0"
 enum_dispatch = "0.3.13"
+log = "0.4.27"
 static_assertions = "1.1.0"
 thiserror = "2.0.12"
diff --git a/fat-bits/src/datetime.rs b/fat-bits/src/datetime.rs
index ecc5309..74f43ea 100644
--- a/fat-bits/src/datetime.rs
+++ b/fat-bits/src/datetime.rs
@@ -1,8 +1,8 @@
 use std::time::SystemTime;
 
-use chrono::{DateTime, Datelike, NaiveDate, NaiveTime, Timelike, Utc};
+use chrono::{DateTime, Datelike, Local, NaiveDate, NaiveTime, Timelike};
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy)]
 pub struct Date {
     repr: u16,
 }
@@ -22,8 +22,7 @@ impl Date {
         Ok(date)
     }
 
-    #[allow(dead_code)]
-    pub fn from_day_month_year(day: u8, month: u8, year: u16) -> anyhow::Result<Date> {
+    fn from_day_month_year(day: u8, month: u8, year: u16) -> anyhow::Result<Date> {
         anyhow::ensure!(day <= 31, "invalid day: {}", day);
         anyhow::ensure!(month <= 12, "invalid month: {}", month);
         anyhow::ensure!(1980 <= year && year <= 2107, "invalid year: {}", year);
@@ -33,10 +32,7 @@ impl Date {
         Ok(Date { repr })
     }
 
-    #[allow(dead_code)]
-    pub fn from_system_time(time: SystemTime) -> anyhow::Result<Date> {
-        let datetime: DateTime<Utc> = time.into();
-
+    pub fn from_datetime(datetime: DateTime<Local>) -> anyhow::Result<Date> {
         let date = datetime.date_naive();
 
         Date::from_day_month_year(
@@ -67,7 +63,7 @@ impl Date {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy)]
 pub struct Time {
     repr: u16,
 }
@@ -79,8 +75,7 @@ impl Time {
         Ok(time)
     }
 
-    #[allow(dead_code)]
-    pub fn from_seconds_minutes_hours(seconds: u8, minutes: u8, hours: u8) -> anyhow::Result<Time> {
+    fn from_seconds_minutes_hours(seconds: u8, minutes: u8, hours: u8) -> anyhow::Result<Time> {
         anyhow::ensure!(seconds <= 58 && seconds % 2 == 0, "invalid seconds: {}", seconds);
         anyhow::ensure!(minutes <= 59, "invalid minutes: {}", minutes);
         anyhow::ensure!(hours <= 23, "invalid hours: {}", hours);
@@ -90,10 +85,7 @@ impl Time {
         Ok(Time { repr })
     }
 
-    #[allow(dead_code)]
-    pub fn from_system_time(time: SystemTime) -> anyhow::Result<Time> {
-        let datetime: DateTime<Utc> = time.into();
-
+    pub fn from_datetime(datetime: DateTime<Local>) -> anyhow::Result<Time> {
         let time = datetime.time();
 
         let seconds = (time.second() as u8) & !0x01;
diff --git a/fat-bits/src/dir.rs b/fat-bits/src/dir.rs
index 4f7e40d..104ba1b 100644
--- a/fat-bits/src/dir.rs
+++ b/fat-bits/src/dir.rs
@@ -1,9 +1,11 @@
 use std::fmt::Display;
 use std::io::{Read, Write};
+use std::time::SystemTime;
 
 use bitflags::bitflags;
-use chrono::{NaiveDate, NaiveDateTime, TimeDelta};
+use chrono::{DateTime, Local, NaiveDate, NaiveDateTime, TimeDelta, Timelike};
 use compact_str::CompactString;
+use log::debug;
 
 use crate::FatFs;
 use crate::datetime::{Date, Time};
@@ -52,7 +54,7 @@ impl Display for Attr {
 /// represents an entry in a diectory
 #[derive(Debug)]
 pub struct DirEntry {
-    name: [u8; 13],
+    name: [u8; 11],
     attr: Attr,
 
     create_time_tenths: u8,
@@ -71,6 +73,8 @@ pub struct DirEntry {
     checksum: u8,
     long_name: Option<CompactString>,
 
+    n_longname_slots: u8,
+
     offset: u64,
 }
 
@@ -96,62 +100,12 @@ impl Display for DirEntry {
 }
 
 impl DirEntry {
-    fn load_name(bytes: [u8; 11], attr: &Attr) -> [u8; 13] {
-        let mut name = [0; 13];
-
-        let mut iter = name.iter_mut();
-
-        if attr.contains(Attr::Hidden) && !attr.contains(Attr::VolumeId) {
-            // hidden file or folder
-            *iter.next().unwrap() = b'.';
-        }
-
-        fn truncate_trailing_spaces(mut bytes: &[u8]) -> &[u8] {
-            while bytes.last() == Some(&0x20) {
-                bytes = &bytes[..bytes.len() - 1];
-            }
-
-            bytes
-        }
-
-        let stem_bytes = truncate_trailing_spaces(&bytes[..8]);
-        let ext_bytes = truncate_trailing_spaces(&bytes[8..]);
-
-        for &c in stem_bytes {
-            let c = match c {
-                // reject non-ascii
-                // TODO: implement code pages? probably not...
-                c if c >= 128 => b'?',
-                c => c,
-            };
-
-            *iter.next().unwrap() = c;
-        }
-
-        if !ext_bytes.is_empty() {
-            *iter.next().unwrap() = b'.';
-
-            for &c in ext_bytes {
-                let c = match c {
-                    // reject non-ascii
-                    // TODO: implement code pages? probably not...
-                    c if c >= 128 => b'?',
-                    c => c,
-                };
-
-                *iter.next().unwrap() = c;
-            }
-        }
-
-        name
-    }
-
     pub fn load(bytes: &[u8], offset: u64) -> anyhow::Result<DirEntry> {
         assert_eq!(bytes.len(), 32);
 
         let attr = Attr::from_bits_truncate(bytes[11]);
 
-        let name = Self::load_name(bytes[..11].try_into().unwrap(), &attr);
+        let name = bytes[..11].try_into().unwrap();
 
         let create_time_tenths = bytes[13];
         anyhow::ensure!(
@@ -200,11 +154,39 @@ impl DirEntry {
             write_date,
             file_size,
             long_name: None,
+            n_longname_slots: 0,
             checksum: Self::checksum(&bytes[..11]),
             offset,
         })
     }
 
+    pub fn create(name: &str, attr: Attr) -> anyhow::Result<Self> {
+        let now: DateTime<Local> = SystemTime::now().into();
+
+        let create_date = Date::from_datetime(now)?;
+        let create_time = Time::from_datetime(now)?;
+        let create_time_tenths = (now.time().nanosecond() / 100_000_000) as u8;
+
+        let name = [0; 11];
+
+        Ok(DirEntry {
+            name,
+            attr,
+            create_time_tenths,
+            create_time,
+            create_date,
+            last_access_date: create_date,
+            first_cluster: 0,
+            write_time: create_time,
+            write_date: create_date,
+            file_size: 0,
+            checksum: Self::checksum(&name),
+            long_name: None,
+            n_longname_slots: 0,
+            offset: !0,
+        })
+    }
+
     fn write(&self, mut writer: impl Write) -> std::io::Result<()> {
         let mut buf = [0; 32];
 
@@ -263,7 +245,7 @@ impl DirEntry {
     }
 
     /// write this DisEntry back to the underlying data
-    pub fn update(&self, fat_fs: &FatFs) -> std::io::Result<()> {
+    pub fn write_back(&self, fat_fs: &FatFs) -> std::io::Result<()> {
         eprintln!("making new SubSliceMut at offset {:#X}", self.offset);
         let sub_slice = SubSliceMut::new(fat_fs.inner.clone(), self.offset, 32);
 
@@ -279,6 +261,8 @@ impl DirEntry {
 
         // paste over with zeros
         sub_slice.write_all(&[0; 31])
+
+        // TODO: erase long filename entries as well
     }
 
     /// indicates this DirEntry is empty
@@ -329,13 +313,7 @@ impl DirEntry {
     }
 
     pub fn name(&self) -> &[u8] {
-        let mut name: &[u8] = &self.name;
-
-        while let Some(&0) = name.last() {
-            name = &name[..name.len() - 1];
-        }
-
-        name
+        &self.name
     }
 
     pub fn stem(&self) -> &[u8] {
@@ -386,7 +364,7 @@ impl DirEntry {
             {
                 '?'
             } else {
-                c as char
+                (c as char).to_ascii_uppercase()
             }
         }
 
@@ -405,8 +383,9 @@ impl DirEntry {
         self.long_name.as_deref()
     }
 
-    pub fn set_long_name(&mut self, long_name: CompactString) {
+    pub fn set_long_name(&mut self, long_name: CompactString, n_slots: u8) {
         self.long_name = Some(long_name);
+        self.n_longname_slots = n_slots;
     }
 
     pub fn attr(&self) -> Attr {
@@ -428,6 +407,15 @@ impl DirEntry {
         self.last_access_date.to_naive_date()
     }
 
+    pub fn update_last_access_date(
+        &mut self,
+        time: impl Into<DateTime<Local>>,
+    ) -> anyhow::Result<()> {
+        self.last_access_date = Date::from_datetime(time.into())?;
+
+        Ok(())
+    }
+
     pub fn first_cluster(&self) -> u32 {
         self.first_cluster
     }
@@ -439,6 +427,15 @@ impl DirEntry {
         NaiveDateTime::new(date, time)
     }
 
+    pub fn update_write_time(&mut self, time: impl Into<DateTime<Local>>) -> anyhow::Result<()> {
+        let time = time.into();
+
+        self.write_date = Date::from_datetime(time)?;
+        self.write_time = Time::from_datetime(time)?;
+
+        Ok(())
+    }
+
     pub fn file_size(&self) -> u32 {
         self.file_size
     }
@@ -461,6 +458,7 @@ impl DirEntry {
 /// long filename entry in a directory
 ///
 /// this should not be exposed to end users, only for internal consumption in the DirIter
+#[derive(Debug)]
 struct LongNameDirEntry {
     ordinal: u8,
     is_last: bool,
@@ -535,6 +533,7 @@ impl LongNameDirEntry {
 ///
 /// should not be exposed publicly, end users only see DirEntries
 /// just for making the bytes -> DirEntry loading a bit easier
+#[derive(Debug)]
 enum DirEntryWrapper {
     Regular(DirEntry),
     LongName(LongNameDirEntry),
@@ -561,6 +560,7 @@ struct LongFilenameBuf {
     rev_buf: Vec<u16>,
     checksum: Option<u8>,
     last_ordinal: Option<u8>,
+    n_slots: u8,
 }
 
 impl LongFilenameBuf {
@@ -568,6 +568,7 @@ impl LongFilenameBuf {
         self.rev_buf.clear();
         self.checksum = None;
         self.last_ordinal = None;
+        self.n_slots = 0;
     }
 
     pub fn next(&mut self, dir_entry: LongNameDirEntry) -> anyhow::Result<()> {
@@ -598,6 +599,8 @@ impl LongFilenameBuf {
             self.checksum = Some(dir_entry.checksum());
             self.last_ordinal = Some(dir_entry.ordinal());
 
+            self.n_slots += 1;
+
             return Ok(());
         }
 
@@ -629,7 +632,10 @@ impl LongFilenameBuf {
         self.rev_buf.extend(name.iter().rev());
     }
 
-    pub fn get_buf(&mut self, checksum: u8) -> anyhow::Result<Option<impl Iterator<Item = u16>>> {
+    pub fn get_buf(
+        &mut self,
+        checksum: u8,
+    ) -> anyhow::Result<Option<(impl Iterator<Item = u16>, u8)>> {
         if self.checksum.is_none() {
             return Ok(None);
         }
@@ -653,7 +659,7 @@ impl LongFilenameBuf {
 
         anyhow::ensure!(self.rev_buf.len() <= 255, "long filename too long");
 
-        Ok(Some(self.rev_buf.iter().copied().rev()))
+        Ok(Some((self.rev_buf.iter().copied().rev(), self.n_slots)))
     }
 }
 
@@ -713,7 +719,7 @@ impl Iterator for DirIter<'_> {
                 return next_impl(me);
             }
 
-            if let Some(iter) = me
+            if let Some((iter, n_slots)) = me
                 .long_filename_buf
                 .get_buf(dir_entry.checksum)
                 .map_err(|e| {
@@ -729,7 +735,7 @@ impl Iterator for DirIter<'_> {
                 let long_filename: CompactString =
                     char::decode_utf16(iter).filter_map(|x| x.ok()).collect();
 
-                dir_entry.set_long_name(long_filename);
+                dir_entry.set_long_name(long_filename, n_slots);
             }
 
             me.long_filename_buf.reset();
@@ -741,7 +747,7 @@ impl Iterator for DirIter<'_> {
             Ok(x) => x,
             Err(e) => {
                 // print error message, try next
-                eprintln!("{}", e);
+                debug!("{}", e);
 
                 self.next()
             }
diff --git a/fat-fuse/Cargo.toml b/fat-fuse/Cargo.toml
index 9a0326c..ad86f43 100644
--- a/fat-fuse/Cargo.toml
+++ b/fat-fuse/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 anyhow = "1.0.98"
+bitflags = "2.9.1"
 chrono = { version = "0.4.41", default-features = false, features = ["alloc", "clock", "std"] }
 compact_string = "0.1.0"
 fat-bits = { version = "0.1.0", path = "../fat-bits" }
diff --git a/fat-fuse/src/fuse.rs b/fat-fuse/src/fuse.rs
index 52cfdd4..feb4dad 100644
--- a/fat-fuse/src/fuse.rs
+++ b/fat-fuse/src/fuse.rs
@@ -1,16 +1,54 @@
 use std::ffi::c_int;
 use std::io::{Read, Write};
-use std::time::Duration;
+use std::time::{Duration, SystemTime};
 
+use bitflags::bitflags;
 use fat_bits::dir::DirEntry;
 use fuser::{FileType, Filesystem};
-use libc::{EBADF, EINVAL, EIO, EISDIR, ENOENT, ENOSYS, ENOTDIR};
+use libc::{EACCES, EBADF, EINVAL, EIO, EISDIR, ENOENT, ENOSYS, ENOTDIR};
 use log::{debug, error};
 
 use crate::FatFuse;
+use crate::inode::InodeRef;
 
 const TTL: Duration = Duration::from_secs(1);
 
+bitflags! {
+    #[derive(Debug)]
+    struct OpenFlags: i32 {
+        const ReadOnly = libc::O_RDONLY;
+        const WriteOnly = libc::O_WRONLY;
+        const ReadWrite = libc::O_RDWR;
+
+        const Read = libc::O_RDONLY | libc::O_RDWR;
+        const Write = libc::O_WRONLY | libc::O_RDWR;
+
+        const Append = libc::O_APPEND;
+        const Create = libc::O_CREAT;
+        const Exclusive = libc::O_EXCL;
+        const Truncate = libc::O_TRUNC;
+
+        const _ = !0;
+    }
+}
+
+fn get_inode_by_fh_or_ino(fat_fuse: &FatFuse, fh: Option<u64>, ino: u64) -> Result<&InodeRef, i32> {
+    fh.map(|fh| {
+        let inode = fat_fuse.get_inode_by_fh(fh).ok_or(EBADF)?;
+
+        let found_ino = inode.borrow().ino();
+
+        if found_ino != ino {
+            debug!("inode associated with fh {} has ino {}, but expected {ino}", fh, found_ino);
+
+            return Err(EBADF);
+        }
+
+        Ok(inode)
+    })
+    .unwrap_or_else(|| fat_fuse.get_inode(ino).ok_or(ENOENT))
+}
+
 impl Filesystem for FatFuse {
     fn init(
         &mut self,
@@ -82,6 +120,8 @@ impl Filesystem for FatFuse {
         reply.entry(&TTL, &attr, generation as u64);
 
         inode.inc_ref_count();
+
+        // TODO: update access time
     }
 
     fn forget(&mut self, _req: &fuser::Request<'_>, ino: u64, nlookup: u64) {
@@ -112,63 +152,81 @@ impl Filesystem for FatFuse {
         fh: Option<u64>,
         reply: fuser::ReplyAttr,
     ) {
-        let inode = if let Some(fh) = fh {
-            let Some(inode) = self.get_inode_by_fh(fh) else {
-                reply.error(EBADF);
+        let inode = match get_inode_by_fh_or_ino(self, fh, ino) {
+            Ok(inode) => inode,
+            Err(err) => {
+                reply.error(err);
                 return;
-            };
-
-            inode
-        } else if let Some(inode) = self.get_inode(ino).cloned() {
-            inode
-        } else {
-            reply.error(ENOENT);
-            return;
+            }
         };
 
-        let inode = inode.borrow();
+        let mut inode = inode.borrow_mut();
 
         let attr = inode.file_attr();
 
+        inode.update_atime(SystemTime::now());
+
         reply.attr(&TTL, &attr);
     }
 
-    #[allow(unused_variables)]
     fn setattr(
         &mut self,
         _req: &fuser::Request<'_>,
         ino: u64,
-        mode: Option<u32>,
-        uid: Option<u32>,
-        gid: Option<u32>,
+        _mode: Option<u32>,
+        _uid: Option<u32>,
+        _gid: Option<u32>,
         size: Option<u64>,
-        _atime: Option<fuser::TimeOrNow>,
-        _mtime: Option<fuser::TimeOrNow>,
+        atime: Option<fuser::TimeOrNow>,
+        mtime: Option<fuser::TimeOrNow>,
         _ctime: Option<std::time::SystemTime>,
         fh: Option<u64>,
         _crtime: Option<std::time::SystemTime>,
         _chgtime: Option<std::time::SystemTime>,
         _bkuptime: Option<std::time::SystemTime>,
-        flags: Option<u32>,
+        _flags: Option<u32>,
         reply: fuser::ReplyAttr,
     ) {
-        // debug!(
-        //     "[Not Implemented] setattr(ino: {:#x?}, mode: {:?}, uid: {:?}, \
-        //     gid: {:?}, size: {:?}, fh: {:?}, flags: {:?})",
-        //     ino, mode, uid, gid, size, fh, flags
-        // );
-        // reply.error(ENOSYS);
-        // return;
-
-        // TODO: implement this properly
-        let Some(inode) = self.get_inode(ino) else {
-            debug!("tried to get inode {ino}, but not found");
-
-            reply.error(ENOENT);
-            return;
+        let inode = match get_inode_by_fh_or_ino(self, fh, ino) {
+            Ok(inode) => inode,
+            Err(err) => {
+                reply.error(err);
+                return;
+            }
         };
 
-        reply.attr(&TTL, &inode.borrow().file_attr());
+        let mut inode = inode.borrow_mut();
+
+        if let Some(new_size) = size {
+            inode.update_size(new_size);
+        }
+
+        if let Some(atime) = atime {
+            let atime = match atime {
+                fuser::TimeOrNow::SpecificTime(system_time) => system_time,
+                fuser::TimeOrNow::Now => SystemTime::now(),
+            };
+
+            inode.update_atime(atime);
+        }
+
+        if let Some(mtime) = mtime {
+            let mtime = match mtime {
+                fuser::TimeOrNow::SpecificTime(system_time) => system_time,
+                fuser::TimeOrNow::Now => SystemTime::now(),
+            };
+
+            inode.update_mtime(mtime);
+        }
+
+        if let Err(err) = inode.write_back(&self.fat_fs) {
+            debug!("writing back inode failed: {err}");
+
+            reply.error(EIO);
+            return;
+        }
+
+        reply.attr(&TTL, &inode.file_attr());
     }
 
     fn readlink(&mut self, _req: &fuser::Request<'_>, ino: u64, reply: fuser::ReplyData) {
@@ -281,12 +339,32 @@ impl Filesystem for FatFuse {
         reply.error(ENOSYS);
     }
 
-    fn open(&mut self, _req: &fuser::Request<'_>, ino: u64, _flags: i32, reply: fuser::ReplyOpen) {
+    fn open(&mut self, _req: &fuser::Request<'_>, ino: u64, flags: i32, reply: fuser::ReplyOpen) {
         if !self.inode_table.contains_key(&ino) {
             reply.error(ENOENT);
             return;
         }
 
+        let flags = OpenFlags::from_bits_truncate(flags);
+
+        debug!("flags: {flags:?}");
+
+        let Some(inode) = self.get_inode(ino).cloned() else {
+            debug!("inode {ino} not found");
+
+            reply.error(ENOENT);
+            return;
+        };
+
+        let mut inode = inode.borrow_mut();
+
+        if flags.intersects(OpenFlags::Write) && inode.is_read_only() {
+            debug!("tried to open read-only inode {ino} with write access");
+
+            reply.error(EACCES);
+            return;
+        }
+
         let fh = self.next_fh();
 
         if let Some(old_ino) = self.ino_by_fh.insert(fh, ino) {
@@ -295,6 +373,18 @@ impl Filesystem for FatFuse {
 
         debug!("opened inode {}: fh {}", ino, fh);
 
+        if flags.contains(OpenFlags::Truncate) {
+            inode.update_size(0);
+            inode.update_mtime(SystemTime::now());
+
+            if let Err(err) = inode.write_back(&self.fat_fs) {
+                debug!("writing back inode failed: {err}");
+
+                reply.error(EIO);
+                return;
+            }
+        }
+
         reply.opened(fh, 0);
     }
 
@@ -327,7 +417,7 @@ impl Filesystem for FatFuse {
             return;
         };
 
-        let inode = inode.borrow();
+        let mut inode = inode.borrow_mut();
 
         if inode.ino() != ino {
             debug!("fh {fh} is associated with inode {} instead of {ino}", inode.ino());
@@ -395,7 +485,11 @@ impl Filesystem for FatFuse {
             debug!("expected to read {size} bytes, but only read {bytes_read}");
         }
 
+        inode.update_atime(SystemTime::now());
+
         reply.data(&buf[..bytes_read]);
+
+        // TODO: update access time
     }
 
     fn write(
@@ -501,14 +595,18 @@ impl Filesystem for FatFuse {
 
             let new_file_size = offset + bytes_written as u64;
 
-            if let Err(err) = inode.update_size(&self.fat_fs, new_file_size) {
-                debug!("error while updating size: {err}");
+            inode.update_size(new_file_size);
+
+            if let Err(err) = inode.write_back(&self.fat_fs) {
+                debug!("error while writing back inode: {err}");
 
                 reply.error(EIO);
                 return;
             }
         }
 
+        // TODO: update write and access time
+
         reply.written(bytes_written as u32);
     }
 
@@ -520,30 +618,34 @@ impl Filesystem for FatFuse {
         _lock_owner: u64,
         reply: fuser::ReplyEmpty,
     ) {
-        // debug!(
-        //     "[Not Implemented] flush(ino: {:#x?}, fh: {}, lock_owner: {:?})",
-        //     ino, fh, lock_owner
-        // );
-        // reply.error(ENOSYS);
-
         debug!("flushing ino={ino} fh={fh}");
 
-        let Some(&found_ino) = self.ino_by_fh.get(&fh) else {
+        let Some(inode) = self.get_inode_by_fh(fh) else {
             debug!("expected fh {fh} to be mapped to ino {ino}, but not found instead");
 
             reply.error(EBADF);
             return;
         };
 
-        if found_ino != ino {
+        let inode = inode.borrow();
+
+        if inode.ino() != ino {
             debug!(
-                "expected fh {fh} to be mapped to ino {ino}, but was mapped to {found_ino} instead"
+                "expected fh {fh} to be mapped to ino {ino}, but was mapped to {} instead",
+                inode.ino()
             );
 
             reply.error(EBADF);
             return;
         }
 
+        if inode.is_dir() {
+            debug!("called flush on directory (ino: {ino}, fh: {fh}");
+
+            reply.error(EISDIR);
+            return;
+        }
+
         reply.ok();
     }
 
@@ -579,11 +681,38 @@ impl Filesystem for FatFuse {
         _req: &fuser::Request<'_>,
         ino: u64,
         fh: u64,
-        datasync: bool,
+        _datasync: bool,
         reply: fuser::ReplyEmpty,
     ) {
-        debug!("[Not Implemented] fsync(ino: {:#x?}, fh: {}, datasync: {})", ino, fh, datasync);
-        reply.error(ENOSYS);
+        debug!("flushing ino={ino} fh={fh}");
+
+        let Some(inode) = self.get_inode_by_fh(fh) else {
+            debug!("expected fh {fh} to be mapped to ino {ino}, but not found instead");
+
+            reply.error(EBADF);
+            return;
+        };
+
+        let inode = inode.borrow();
+
+        if inode.ino() != ino {
+            debug!(
+                "expected fh {fh} to be mapped to ino {ino}, but was mapped to {} instead",
+                inode.ino()
+            );
+
+            reply.error(EBADF);
+            return;
+        }
+
+        if !inode.is_dir() {
+            debug!("called fsync on directory (ino: {ino}, fh: {fh}");
+
+            reply.error(EISDIR);
+            return;
+        }
+
+        reply.ok();
     }
 
     fn opendir(
@@ -614,7 +743,7 @@ impl Filesystem for FatFuse {
             return;
         };
 
-        let Some(dir_inode) = self.get_inode_by_fh(fh) else {
+        let Some(dir_inode) = self.get_inode_by_fh(fh).cloned() else {
             debug!("could not find inode accociated with fh {} (ino: {})", fh, ino);
 
             reply.error(EBADF);
@@ -685,6 +814,8 @@ impl Filesystem for FatFuse {
         }
 
         reply.ok();
+
+        // TODO: update access time
     }
 
     fn readdirplus(
@@ -774,20 +905,4 @@ impl Filesystem for FatFuse {
         );
         reply.error(ENOSYS);
     }
-
-    fn lseek(
-        &mut self,
-        _req: &fuser::Request<'_>,
-        ino: u64,
-        fh: u64,
-        offset: i64,
-        whence: i32,
-        reply: fuser::ReplyLseek,
-    ) {
-        debug!(
-            "[Not Implemented] lseek(ino: {:#x?}, fh: {}, offset: {}, whence: {})",
-            ino, fh, offset, whence
-        );
-        reply.error(ENOSYS);
-    }
 }
diff --git a/fat-fuse/src/inode.rs b/fat-fuse/src/inode.rs
index 59352a4..fa059d8 100644
--- a/fat-fuse/src/inode.rs
+++ b/fat-fuse/src/inode.rs
@@ -60,29 +60,42 @@ pub struct Inode {
 
     ref_count: u64,
 
+    uid: u32,
+    gid: u32,
+
+    path: Rc<str>,
+
     parent: Option<InodeRef>,
 
-    size: u64,
     block_size: u32,
 
     kind: Kind,
 
     read_only: bool,
 
+    dirty: bool,
+
+    // these are the fields that have to get written back to the DirEntry on write_back
+    size: u64,
+
     atime: SystemTime,
     mtime: SystemTime,
-    // ctime: SystemTime,
     crtime: SystemTime,
 
-    uid: u32,
-    gid: u32,
-
     first_cluster: u32,
-
-    path: Rc<str>,
 }
 
-#[allow(dead_code)]
+impl Drop for Inode {
+    fn drop(&mut self) {
+        // since we don't have a handle on the FatFs we can't do the write-back here
+        assert!(
+            !self.dirty,
+            "inode {} is dirty, but was not written back to FS before being destroyed",
+            self.ino()
+        );
+    }
+}
+
 impl Inode {
     fn new_generation() -> u32 {
         let rand: u16 = get_random();
@@ -144,6 +157,7 @@ impl Inode {
             block_size: fat_fs.bytes_per_sector() as u32,
             kind,
             read_only: dir_entry.is_readonly(),
+            dirty: false,
             atime,
             mtime,
             crtime,
@@ -166,6 +180,7 @@ impl Inode {
             block_size: fat_fs.bytes_per_sector() as u32,
             kind: Kind::Dir,
             read_only: false,
+            dirty: false,
             atime: SystemTime::UNIX_EPOCH,
             mtime: SystemTime::UNIX_EPOCH,
             crtime: SystemTime::UNIX_EPOCH,
@@ -228,39 +243,6 @@ impl Inode {
         self.size
     }
 
-    pub fn update_size(&mut self, fat_fs: &FatFs, new_size: u64) -> anyhow::Result<()> {
-        let Some(parent_inode) = self.parent() else {
-            anyhow::bail!("parent inode of {} does not exist", self.ino);
-        };
-
-        let parent_inode = parent_inode.borrow();
-
-        // since we just wrote to the file with this inode, first cluster should not be zero
-        let Some(mut dir_entry) = parent_inode
-            .dir_iter(fat_fs)
-            .unwrap()
-            .find(|dir_entry| dir_entry.first_cluster() == self.first_cluster())
-        else {
-            anyhow::bail!("could not find dir_entry corresponding to self in parent inode");
-        };
-
-        debug!("new file size: {new_size}");
-
-        assert!(new_size <= u32::MAX as u64);
-
-        dir_entry.update_file_size(new_size as u32);
-
-        if dir_entry.update(fat_fs).is_err() {
-            anyhow::bail!("failed to update dir_entry for inode {}", self.ino);
-        }
-
-        drop(parent_inode);
-
-        self.size = new_size;
-
-        Ok(())
-    }
-
     pub fn kind(&self) -> Kind {
         self.kind
     }
@@ -346,9 +328,67 @@ impl Inode {
         Ok(fat_fs.file_writer(self.first_cluster()))
     }
 
-    // pub fn write_back(&self, fat_fs: &FatFs) {
-    //     // let
+    pub fn update_size(&mut self, new_size: u64) {
+        self.size = new_size;
+        self.dirty = true;
+    }
 
-    //     todo!()
-    // }
+    pub fn update_atime(&mut self, atime: SystemTime) {
+        self.atime = atime;
+        self.dirty = true;
+    }
+
+    pub fn update_mtime(&mut self, mtime: SystemTime) {
+        self.mtime = mtime;
+        self.dirty = true;
+    }
+
+    pub fn write_back(&mut self, fat_fs: &FatFs) -> anyhow::Result<()> {
+        if !self.dirty {
+            return Ok(());
+        }
+
+        let Some(parent_inode) = self.parent() else {
+            anyhow::bail!("parent inode of {} does not exist", self.ino);
+        };
+
+        let parent_inode = parent_inode.borrow();
+
+        // since we just wrote to the file with this inode, first cluster should not be zero
+        let Some(mut dir_entry) = parent_inode
+            .dir_iter(fat_fs)
+            .unwrap()
+            .find(|dir_entry| dir_entry.first_cluster() == self.first_cluster())
+        else {
+            anyhow::bail!("could not find dir_entry corresponding to self in parent inode");
+        };
+
+        drop(parent_inode);
+
+        // update stats on DirEntry
+        assert!(self.size <= u32::MAX as u64);
+
+        dir_entry.update_file_size(self.size as u32);
+
+        dir_entry
+            .update_last_access_date(self.atime)
+            .map_err(|err| {
+                anyhow::anyhow!("failed to update atime for inode {}: {err}", self.ino)
+            })?;
+
+        dir_entry.update_write_time(self.mtime).map_err(|err| {
+            anyhow::anyhow!("failed to update mtime for inode {}: {err}", self.ino)
+        })?;
+
+        // update cr_time as well?
+
+        // write DirEntry back to device
+        dir_entry.write_back(fat_fs).map_err(|err| {
+            anyhow::anyhow!("failed to write back dir_entry for inode {}: {err}", self.ino)
+        })?;
+
+        self.dirty = false;
+
+        Ok(())
+    }
 }
diff --git a/fat-fuse/src/lib.rs b/fat-fuse/src/lib.rs
index 4ef5dae..9c4ca3f 100644
--- a/fat-fuse/src/lib.rs
+++ b/fat-fuse/src/lib.rs
@@ -271,10 +271,10 @@ impl FatFuse {
         }
     }
 
-    pub fn get_inode_by_fh(&self, fh: u64) -> Option<InodeRef> {
+    pub fn get_inode_by_fh(&self, fh: u64) -> Option<&InodeRef> {
         let ino = *self.ino_by_fh.get(&fh)?;
 
-        if let Some(inode) = self.get_inode(ino).cloned() {
+        if let Some(inode) = self.get_inode(ino) {
             Some(inode)
         } else {
             debug!("fh {} is mapped to ino {}, but inode is not in table", fh, ino);