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Message-ID: <176169817873.1429568.4805622485351937995.stgit@frogsfrogsfrogs>
Date: Tue, 28 Oct 2025 18:12:51 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: linux-fsdevel@...r.kernel.org, joannelkoong@...il.com, bernd@...ernd.com,
neal@...pa.dev, miklos@...redi.hu, linux-ext4@...r.kernel.org
Subject: [PATCH 17/17] fuse2fs: enable atomic writes
From: Darrick J. Wong <djwong@...nel.org>
Advertise the single-fsblock atomic write capability that iomap can do.
Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
fuse4fs/fuse4fs.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++
misc/fuse2fs.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 134 insertions(+), 2 deletions(-)
diff --git a/fuse4fs/fuse4fs.c b/fuse4fs/fuse4fs.c
index 564b3fc75a31c0..544ad9ecb06d45 100644
--- a/fuse4fs/fuse4fs.c
+++ b/fuse4fs/fuse4fs.c
@@ -285,6 +285,9 @@ struct fuse4fs {
void (*old_alloc_stats)(ext2_filsys fs, blk64_t blk, int inuse);
void (*old_alloc_stats_range)(ext2_filsys fs, blk64_t blk, blk_t num,
int inuse);
+#ifdef STATX_WRITE_ATOMIC
+ unsigned int awu_min, awu_max;
+#endif
#endif
unsigned int blockmask;
unsigned long offset;
@@ -910,10 +913,22 @@ static inline bool fuse4fs_can_iomap(const struct fuse4fs *ff)
{
return ff->iomap_cap & FUSE_IOMAP_SUPPORT_FILEIO;
}
+
+static inline bool fuse4fs_iomap_supports_hw_atomic(const struct fuse4fs *ff)
+{
+ return fuse4fs_iomap_enabled(ff) &&
+ (ff->iomap_cap & FUSE_IOMAP_SUPPORT_ATOMIC) &&
+#ifdef STATX_WRITE_ATOMIC
+ ff->awu_min > 0 && ff->awu_min > 0;
+#else
+ 0;
+#endif
+}
#else
# define fuse4fs_iomap_enabled(...) (0)
# define fuse4fs_discover_iomap(...) ((void)0)
# define fuse4fs_can_iomap(...) (false)
+# define fuse4fs_iomap_supports_hw_atomic(...) (0)
#endif
static inline void fuse4fs_dump_extents(struct fuse4fs *ff, ext2_ino_t ino,
@@ -2109,8 +2124,12 @@ static int fuse4fs_stat_inode(struct fuse4fs *ff, ext2_ino_t ino,
fstat->iflags = 0;
#ifdef HAVE_FUSE_IOMAP
- if (fuse4fs_iomap_enabled(ff))
+ if (fuse4fs_iomap_enabled(ff)) {
fstat->iflags |= FUSE_IFLAG_IOMAP;
+
+ if (fuse4fs_iomap_supports_hw_atomic(ff))
+ fstat->iflags |= FUSE_IFLAG_ATOMIC;
+ }
#endif
return 0;
@@ -2288,6 +2307,15 @@ static int fuse4fs_statx(struct fuse4fs *ff, ext2_ino_t ino, int statx_mask,
fuse4fs_statx_directio(ff, stx);
+#ifdef STATX_WRITE_ATOMIC
+ if (fuse4fs_iomap_supports_hw_atomic(ff)) {
+ stx->stx_mask |= STATX_WRITE_ATOMIC;
+ stx->stx_atomic_write_unit_min = ff->awu_min;
+ stx->stx_atomic_write_unit_max = ff->awu_max;
+ stx->stx_atomic_write_segments_max = 1;
+ }
+#endif
+
return 0;
}
@@ -6664,6 +6692,9 @@ static void op_iomap_begin(fuse_req_t req, fuse_ino_t fino, uint64_t dontcare,
}
}
+ if (opflags & FUSE_IOMAP_OP_ATOMIC)
+ read.flags |= FUSE_IOMAP_F_ATOMIC_BIO;
+
out_unlock:
fuse4fs_finish(ff, ret);
if (ret)
@@ -6828,6 +6859,38 @@ static int fuse4fs_set_bdev_blocksize(struct fuse4fs *ff, int fd)
return -EIO;
}
+#ifdef STATX_WRITE_ATOMIC
+static void fuse4fs_configure_atomic_write(struct fuse4fs *ff, int bdev_fd)
+{
+ struct statx devx;
+ unsigned int awu_min, awu_max;
+ int ret;
+
+ if (!ext2fs_has_feature_extents(ff->fs->super))
+ return;
+
+ ret = statx(bdev_fd, "", AT_EMPTY_PATH, STATX_WRITE_ATOMIC, &devx);
+ if (ret)
+ return;
+ if (!(devx.stx_mask & STATX_WRITE_ATOMIC))
+ return;
+
+ awu_min = max(ff->fs->blocksize, devx.stx_atomic_write_unit_min);
+ awu_max = min(ff->fs->blocksize, devx.stx_atomic_write_unit_max);
+ if (awu_min > awu_max)
+ return;
+
+ log_printf(ff, "%s awu_min: %u, awu_max: %u\n",
+ _("Supports (experimental) DIO atomic writes"),
+ awu_min, awu_max);
+
+ ff->awu_min = awu_min;
+ ff->awu_max = awu_max;
+}
+#else
+# define fuse4fs_configure_atomic_write(...) ((void)0)
+#endif
+
static int fuse4fs_iomap_config_devices(struct fuse4fs *ff)
{
errcode_t err;
@@ -6852,6 +6915,8 @@ static int fuse4fs_iomap_config_devices(struct fuse4fs *ff)
dbg_printf(ff, "%s: registered iomap dev fd=%d iomap_dev=%u\n",
__func__, fd, ff->iomap_dev);
+ fuse4fs_configure_atomic_write(ff, fd);
+
ff->iomap_dev = ret;
return 0;
}
diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index a8887c9ead9d9b..e6853a9be7dd03 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -279,6 +279,9 @@ struct fuse2fs {
void (*old_alloc_stats)(ext2_filsys fs, blk64_t blk, int inuse);
void (*old_alloc_stats_range)(ext2_filsys fs, blk64_t blk, blk_t num,
int inuse);
+#ifdef STATX_WRITE_ATOMIC
+ unsigned int awu_min, awu_max;
+#endif
#endif
unsigned int blockmask;
unsigned long offset;
@@ -749,10 +752,22 @@ static inline bool fuse2fs_can_iomap(const struct fuse2fs *ff)
{
return ff->iomap_cap & FUSE_IOMAP_SUPPORT_FILEIO;
}
+
+static inline bool fuse2fs_iomap_supports_hw_atomic(const struct fuse2fs *ff)
+{
+ return fuse2fs_iomap_enabled(ff) &&
+ (ff->iomap_cap & FUSE_IOMAP_SUPPORT_ATOMIC) &&
+#ifdef STATX_WRITE_ATOMIC
+ ff->awu_min > 0 && ff->awu_min > 0;
+#else
+ 0;
+#endif
+}
#else
# define fuse2fs_iomap_enabled(...) (0)
# define fuse2fs_discover_iomap(...) ((void)0)
# define fuse2fs_can_iomap(...) (false)
+# define fuse2fs_iomap_supports_hw_atomic(...) (0)
#endif
static inline void fuse2fs_dump_extents(struct fuse2fs *ff, ext2_ino_t ino,
@@ -1980,14 +1995,19 @@ static int op_getattr(const char *path, struct stat *statbuf,
static int op_getattr_iflags(const char *path, struct stat *statbuf,
unsigned int *iflags, struct fuse_file_info *fi)
{
+ struct fuse2fs *ff = fuse2fs_get();
int ret = op_getattr(path, statbuf, fi);
if (ret)
return ret;
- if (fuse_fs_can_enable_iomap(statbuf))
+ if (fuse_fs_can_enable_iomap(statbuf)) {
*iflags |= FUSE_IFLAG_IOMAP;
+ if (fuse2fs_iomap_supports_hw_atomic(ff))
+ *iflags |= FUSE_IFLAG_ATOMIC;
+ }
+
return 0;
}
#endif
@@ -2096,6 +2116,16 @@ static int fuse2fs_statx(struct fuse2fs *ff, ext2_ino_t ino, int statx_mask,
fuse2fs_statx_directio(ff, stx);
+#ifdef STATX_WRITE_ATOMIC
+ if (fuse_fs_can_enable_iomapx(stx) &&
+ fuse2fs_iomap_supports_hw_atomic(ff)) {
+ stx->stx_mask |= STATX_WRITE_ATOMIC;
+ stx->stx_atomic_write_unit_min = ff->awu_min;
+ stx->stx_atomic_write_unit_max = ff->awu_max;
+ stx->stx_atomic_write_segments_max = 1;
+ }
+#endif
+
return 0;
}
@@ -6195,6 +6225,9 @@ static int op_iomap_begin(const char *path, uint64_t nodeid, uint64_t attr_ino,
}
}
+ if (opflags & FUSE_IOMAP_OP_ATOMIC)
+ read->flags |= FUSE_IOMAP_F_ATOMIC_BIO;
+
out_unlock:
fuse2fs_finish(ff, ret);
return ret;
@@ -6356,6 +6389,38 @@ static int fuse2fs_set_bdev_blocksize(struct fuse2fs *ff, int fd)
return -EIO;
}
+#ifdef STATX_WRITE_ATOMIC
+static void fuse2fs_configure_atomic_write(struct fuse2fs *ff, int bdev_fd)
+{
+ struct statx devx;
+ unsigned int awu_min, awu_max;
+ int ret;
+
+ if (!ext2fs_has_feature_extents(ff->fs->super))
+ return;
+
+ ret = statx(bdev_fd, "", AT_EMPTY_PATH, STATX_WRITE_ATOMIC, &devx);
+ if (ret)
+ return;
+ if (!(devx.stx_mask & STATX_WRITE_ATOMIC))
+ return;
+
+ awu_min = max(ff->fs->blocksize, devx.stx_atomic_write_unit_min);
+ awu_max = min(ff->fs->blocksize, devx.stx_atomic_write_unit_max);
+ if (awu_min > awu_max)
+ return;
+
+ log_printf(ff, "%s awu_min: %u, awu_max: %u\n",
+ _("Supports (experimental) DIO atomic writes"),
+ awu_min, awu_max);
+
+ ff->awu_min = awu_min;
+ ff->awu_max = awu_max;
+}
+#else
+# define fuse2fs_configure_atomic_write(...) ((void)0)
+#endif
+
static int fuse2fs_iomap_config_devices(struct fuse2fs *ff)
{
errcode_t err;
@@ -6380,6 +6445,8 @@ static int fuse2fs_iomap_config_devices(struct fuse2fs *ff)
dbg_printf(ff, "%s: registered iomap dev fd=%d iomap_dev=%u\n",
__func__, fd, ff->iomap_dev);
+ fuse2fs_configure_atomic_write(ff, fd);
+
ff->iomap_dev = ret;
return 0;
}
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