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Message-ID: <176169810937.1424854.17545235254390180266.stgit@frogsfrogsfrogs>
Date: Tue, 28 Oct 2025 17:51:59 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: djwong@...nel.org, miklos@...redi.hu
Cc: joannelkoong@...il.com, bernd@...ernd.com, neal@...pa.dev,
linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 27/31] fuse: support atomic writes with iomap
From: Darrick J. Wong <djwong@...nel.org>
Enable untorn writes of up to a single fsblock, if iomap is enabled.
Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
fs/fuse/fuse_i.h | 9 +++++++++
include/uapi/linux/fuse.h | 5 +++++
fs/fuse/file_iomap.c | 46 ++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 59 insertions(+), 1 deletion(-)
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index f6b6944fad553c..9ab1de8063c05e 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -266,6 +266,8 @@ enum {
FUSE_I_EXCLUSIVE,
/* Use iomap for this inode */
FUSE_I_IOMAP,
+ /* Enable untorn writes */
+ FUSE_I_ATOMIC,
};
struct fuse_conn;
@@ -1768,6 +1770,13 @@ static inline bool fuse_inode_has_iomap(const struct inode *inode)
return test_bit(FUSE_I_IOMAP, &fi->state);
}
+static inline bool fuse_inode_has_atomic(const struct inode *inode)
+{
+ const struct fuse_inode *fi = get_fuse_inode(inode);
+
+ return test_bit(FUSE_I_ATOMIC, &fi->state);
+}
+
int fuse_iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 length);
loff_t fuse_iomap_lseek(struct file *file, loff_t offset, int whence);
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 838d925d2947e0..99ad2367d1dc20 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -246,6 +246,7 @@
* - add FUSE_ATTR_IOMAP to enable iomap for specific inodes
* - add FUSE_IOMAP_CONFIG so the fuse server can configure more fs geometry
* - add FUSE_NOTIFY_IOMAP_DEV_INVAL to invalidate iomap bdev ranges
+ * - add FUSE_ATTR_ATOMIC for single-fsblock atomic write support
*/
#ifndef _LINUX_FUSE_H
@@ -600,10 +601,12 @@ struct fuse_file_lock {
* FUSE_ATTR_SUBMOUNT: Object is a submount root
* FUSE_ATTR_DAX: Enable DAX for this file in per inode DAX mode
* FUSE_ATTR_IOMAP: Use iomap for this inode
+ * FUSE_ATTR_ATOMIC: Enable untorn writes
*/
#define FUSE_ATTR_SUBMOUNT (1 << 0)
#define FUSE_ATTR_DAX (1 << 1)
#define FUSE_ATTR_IOMAP (1 << 2)
+#define FUSE_ATTR_ATOMIC (1 << 3)
/**
* Open flags
@@ -1171,6 +1174,8 @@ struct fuse_backing_map {
/* basic file I/O functionality through iomap */
#define FUSE_IOMAP_SUPPORT_FILEIO (1ULL << 0)
+/* untorn writes through iomap */
+#define FUSE_IOMAP_SUPPORT_ATOMIC (1ULL << 1)
struct fuse_iomap_support {
uint64_t flags;
uint64_t padding;
diff --git a/fs/fuse/file_iomap.c b/fs/fuse/file_iomap.c
index 06d1834e43f698..f4cb9dcde445ef 100644
--- a/fs/fuse/file_iomap.c
+++ b/fs/fuse/file_iomap.c
@@ -1099,6 +1099,20 @@ static inline void fuse_inode_clear_iomap(struct inode *inode)
clear_bit(FUSE_I_IOMAP, &fi->state);
}
+static inline void fuse_inode_set_atomic(struct inode *inode)
+{
+ struct fuse_inode *fi = get_fuse_inode(inode);
+
+ set_bit(FUSE_I_ATOMIC, &fi->state);
+}
+
+static inline void fuse_inode_clear_atomic(struct inode *inode)
+{
+ struct fuse_inode *fi = get_fuse_inode(inode);
+
+ clear_bit(FUSE_I_ATOMIC, &fi->state);
+}
+
void fuse_iomap_init_nonreg_inode(struct inode *inode, unsigned attr_flags)
{
struct fuse_conn *conn = get_fuse_conn(inode);
@@ -1122,6 +1136,8 @@ void fuse_iomap_init_reg_inode(struct inode *inode, unsigned attr_flags)
if (conn->iomap && (attr_flags & FUSE_ATTR_IOMAP)) {
set_bit(FUSE_I_EXCLUSIVE, &fi->state);
fuse_inode_set_iomap(inode);
+ if (attr_flags & FUSE_ATTR_ATOMIC)
+ fuse_inode_set_atomic(inode);
}
trace_fuse_iomap_init_inode(inode);
@@ -1134,6 +1150,8 @@ void fuse_iomap_evict_inode(struct inode *inode)
trace_fuse_iomap_evict_inode(inode);
+ if (fuse_inode_has_atomic(inode))
+ fuse_inode_clear_atomic(inode);
if (fuse_inode_has_iomap(inode))
fuse_inode_clear_iomap(inode);
if (conn->iomap && fuse_inode_is_exclusive(inode))
@@ -1214,6 +1232,8 @@ void fuse_iomap_open(struct inode *inode, struct file *file)
ASSERT(fuse_inode_has_iomap(inode));
file->f_mode |= FMODE_NOWAIT | FMODE_CAN_ODIRECT;
+ if (fuse_inode_has_atomic(inode))
+ file->f_mode |= FMODE_CAN_ATOMIC_WRITE;
}
enum fuse_ilock_type {
@@ -1420,6 +1440,17 @@ fuse_iomap_write_checks(
return kiocb_modified(iocb);
}
+static inline ssize_t fuse_iomap_atomic_write_valid(struct kiocb *iocb,
+ struct iov_iter *from)
+{
+ struct inode *inode = file_inode(iocb->ki_filp);
+
+ if (iov_iter_count(from) != i_blocksize(inode))
+ return -EINVAL;
+
+ return generic_atomic_write_valid(iocb, from);
+}
+
ssize_t fuse_iomap_direct_write(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
@@ -1435,6 +1466,12 @@ ssize_t fuse_iomap_direct_write(struct kiocb *iocb, struct iov_iter *from)
if (!count)
return 0;
+ if (iocb->ki_flags & IOCB_ATOMIC) {
+ ret = fuse_iomap_atomic_write_valid(iocb, from);
+ if (ret)
+ return ret;
+ }
+
/*
* Unaligned direct writes require zeroing of unwritten head and tail
* blocks. Extending writes require zeroing of post-EOF tail blocks.
@@ -1840,6 +1877,12 @@ ssize_t fuse_iomap_buffered_write(struct kiocb *iocb, struct iov_iter *from)
if (!iov_iter_count(from))
return 0;
+ if (iocb->ki_flags & IOCB_ATOMIC) {
+ ret = fuse_iomap_atomic_write_valid(iocb, from);
+ if (ret)
+ return ret;
+ }
+
ret = fuse_iomap_ilock_iocb(iocb, EXCL);
if (ret)
return ret;
@@ -2063,7 +2106,8 @@ int fuse_dev_ioctl_iomap_support(struct file *file,
struct fuse_iomap_support ios = { };
if (fuse_iomap_enabled())
- ios.flags = FUSE_IOMAP_SUPPORT_FILEIO;
+ ios.flags = FUSE_IOMAP_SUPPORT_FILEIO |
+ FUSE_IOMAP_SUPPORT_ATOMIC;
if (copy_to_user(argp, &ios, sizeof(ios)))
return -EFAULT;
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