[PATCH 1/9] fuse: enable caching of timestamps

Darrick J. Wong
2025-09-16T00:36:19Z

Cache the timestamps in the kernel so that the kernel sends FUSE_SETATTR
calls to the fuse server after writes, because the iomap infrastructure
won't do that for us.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
fs/fuse/dir.c | 5 ++++-
fs/fuse/file.c | 18 ++++++++++++------
fs/fuse/file_iomap.c | 6 ++++++
fs/fuse/inode.c | 13 +++++++------
4 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index c6e83b724f8cd0..380559950c3444 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -2062,7 +2062,8 @@ int fuse_do_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
struct fuse_attr_out outarg;
const bool is_iomap = fuse_inode_has_iomap(inode);
bool is_truncate = false;
- bool is_wb = fc->writeback_cache && S_ISREG(inode->i_mode);
+ bool is_wb = (is_iomap || fc->writeback_cache) &&
+ S_ISREG(inode->i_mode);
loff_t oldsize;
int err;
bool trust_local_cmtime = is_wb;
@@ -2196,6 +2197,8 @@ int fuse_do_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
spin_lock(&fi->lock);
/* the kernel maintains i_mtime locally */
if (trust_local_cmtime) {
+ if ((attr->ia_valid & ATTR_ATIME) && is_iomap)
+ inode_set_atime_to_ts(inode, attr->ia_atime);
if (attr->ia_valid & ATTR_MTIME)
inode_set_mtime_to_ts(inode, attr->ia_mtime);
if (attr->ia_valid & ATTR_CTIME)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 9476f14035bb7f..0ed13082d0d00d 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -240,7 +240,7 @@ static int fuse_open(struct inode *inode, struct file *file)
int err;
const bool is_iomap = fuse_inode_has_iomap(inode);
bool is_truncate = (file->f_flags & O_TRUNC) && fc->atomic_o_trunc;
- bool is_wb_truncate = is_truncate && fc->writeback_cache;
+ bool is_wb_truncate = is_truncate && (is_iomap || fc->writeback_cache);
bool dax_truncate = is_truncate && FUSE_IS_DAX(inode);

if (fuse_is_bad(inode))
@@ -453,12 +453,14 @@ static int fuse_flush(struct file *file, fl_owner_t id)
struct fuse_file *ff = file->private_data;
struct fuse_flush_in inarg;
FUSE_ARGS(args);
+ const bool is_iomap = fuse_inode_has_iomap(inode);
int err;

if (fuse_is_bad(inode))
return -EIO;

- if (ff->open_flags & FOPEN_NOFLUSH && !fm->fc->writeback_cache)
+ if ((ff->open_flags & FOPEN_NOFLUSH) &&
+ !fm->fc->writeback_cache && !is_iomap)
return 0;

err = write_inode_now(inode, 1);
@@ -494,7 +496,7 @@ static int fuse_flush(struct file *file, fl_owner_t id)
* In memory i_blocks is not maintained by fuse, if writeback cache is
* enabled, i_blocks from cached attr may not be accurate.
*/
- if (!err && fm->fc->writeback_cache)
+ if (!err && (is_iomap || fm->fc->writeback_cache))
fuse_invalidate_attr_mask(inode, STATX_BLOCKS);
return err;
}
@@ -796,8 +798,10 @@ static void fuse_short_read(struct inode *inode, u64 attr_ver, size_t num_read,
* If writeback_cache is enabled, a short read means there's a hole in
* the file. Some data after the hole is in page cache, but has not
* reached the client fs yet. So the hole is not present there.
+ * If iomap is enabled, a short read means we hit EOF so there's
+ * nothing to adjust.
*/
- if (!fc->writeback_cache) {
+ if (!fc->writeback_cache && !fuse_inode_has_iomap(inode)) {
loff_t pos = folio_pos(ap->folios[0]) + num_read;
fuse_read_update_size(inode, pos, attr_ver);
}
@@ -1412,6 +1416,8 @@ static int fuse_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
unsigned int flags, struct iomap *iomap,
struct iomap *srcmap)
{
+ WARN_ON(fuse_inode_has_iomap(inode));
+
iomap->type = IOMAP_MAPPED;
iomap->length = length;
iomap->offset = offset;
@@ -1979,7 +1985,7 @@ static void fuse_writepage_end(struct fuse_mount *fm, struct fuse_args *args,
* Do this only if writeback_cache is not enabled. If writeback_cache
* is enabled, we trust local ctime/mtime.
*/
- if (!fc->writeback_cache)
+ if (!fc->writeback_cache && !fuse_inode_has_iomap(inode))
fuse_invalidate_attr_mask(inode, FUSE_STATX_MODIFY);
spin_lock(&fi->lock);
fi->writectr--;
@@ -3065,7 +3071,7 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
/* mark unstable when write-back is not used, and file_out gets
* extended */
const bool is_iomap = fuse_inode_has_iomap(inode_out);
- bool is_unstable = (!fc->writeback_cache) &&
+ bool is_unstable = (!fc->writeback_cache && !is_iomap) &&
((pos_out + len) > inode_out->i_size);

if (fc->no_copy_file_range)
diff --git a/fs/fuse/file_iomap.c b/fs/fuse/file_iomap.c
index 524c26e53674f2..1fc9a9b7b75094 100644
--- a/fs/fuse/file_iomap.c
+++ b/fs/fuse/file_iomap.c
@@ -1769,6 +1769,12 @@ static inline void fuse_inode_set_iomap(struct inode *inode)

ASSERT(fuse_has_iomap(inode));

+ /*
+ * Manage timestamps ourselves, don't make the fuse server do it. This
+ * is critical for mtime updates to work correctly with page_mkwrite.
+ */
+ inode->i_flags &= ~S_NOCMTIME;
+ inode->i_flags &= ~S_NOATIME;
inode->i_data.a_ops = &fuse_iomap_aops;

INIT_WORK(&fi->ioend_work, fuse_iomap_end_io);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index e74d39ac05a570..b63e4e1d8f45ce 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -328,10 +328,11 @@ u32 fuse_get_cache_mask(struct inode *inode)
{
struct fuse_conn *fc = get_fuse_conn(inode);

- if (!fc->writeback_cache || !S_ISREG(inode->i_mode))
- return 0;
+ if (S_ISREG(inode->i_mode) &&
+ (fuse_inode_has_iomap(inode) || fc->writeback_cache))
+ return STATX_MTIME | STATX_CTIME | STATX_SIZE;

- return STATX_MTIME | STATX_CTIME | STATX_SIZE;
+ return 0;
}

static void fuse_change_attributes_i(struct inode *inode, struct fuse_attr *attr,
@@ -346,9 +347,9 @@ static void fuse_change_attributes_i(struct inode *inode, struct fuse_attr *attr

spin_lock(&fi->lock);
/*
- * In case of writeback_cache enabled, writes update mtime, ctime and
- * may update i_size. In these cases trust the cached value in the
- * inode.
+ * In case of writeback_cache or iomap enabled, writes update mtime,
+ * ctime and may update i_size. In these cases trust the cached value
+ * in the inode.
*/
cache_mask = fuse_get_cache_mask(inode);
if (cache_mask & STATX_SIZE)