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

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

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 bd0d37a513b42d..4bfc8fe52532a6 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -2055,7 +2055,8 @@ 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;
@@ -2189,6 +2190,8 @@ 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 8a2daee7e58e27..98beba35743268 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);
 	}
@@ -1409,6 +1413,8 @@ 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;
@@ -1972,7 +1978,7 @@ 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--;
@@ -3057,7 +3063,7 @@ 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 f7459a0c138c12..53c907dbba2a05 100644
--- a/fs/fuse/file_iomap.c
+++ b/fs/fuse/file_iomap.c
@@ -1834,6 +1834,12 @@ static inline void fuse_inode_set_iomap(struct inode *inode)
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	unsigned int min_order = 0;
 
+	/*
+	 * 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 955c1b23b1f9cb..2fc75719969a89 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -326,10 +326,11 @@ 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,
@@ -344,9 +345,9 @@ 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)