Re: Re: Re: [RFC PATCH] fuse: support cache revalidation in writeback_cache mode

From: Miklos Szeredi
Date: Tue Apr 26 2022 - 09:09:23 EST

Next message: Martin K. Petersen: "Re: [PATCH] scsi: ufs: using pm_runtime_resume_and_get instead of pm_runtime_get_sync"
Previous message: Sandipan Das: "[PATCH v3 7/7] kvm: x86/cpuid: Fix CPUID leaf 0xA"
In reply to: Jiachen Zhang: "Re: Re: Re: [RFC PATCH] fuse: support cache revalidation in writeback_cache mode"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

On Mon, Apr 25, 2022 at 09:52:44PM +0800, Jiachen Zhang wrote:

> Some users may want both the high performance of writeback mode and a
> little bit more consistency among FUSE mounts. In the current
> writeback mode implementation, users of one FUSE mount can never see
> the file expansion done by other FUSE mounts.

Okay.

Here's a preliminary patch that you could try.

Thanks,
Miklos

---
fs/fuse/dir.c | 35 ++++++++++++++++++++++-------------
fs/fuse/file.c | 17 +++++++++++++++--
fs/fuse/fuse_i.h | 14 +++++++++++++-
fs/fuse/inode.c | 32 +++++++++++++++++++++++++++-----
include/uapi/linux/fuse.h | 5 +++++
5 files changed, 82 insertions(+), 21 deletions(-)

--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -194,6 +194,7 @@
* - add FUSE_SECURITY_CTX init flag
* - add security context to create, mkdir, symlink, and mknod requests
* - add FUSE_HAS_INODE_DAX, FUSE_ATTR_DAX
+ * - add FUSE_WRITEBACK_CACHE_V2 init flag
*/

#ifndef _LINUX_FUSE_H
@@ -353,6 +354,9 @@ struct fuse_file_lock {
* FUSE_SECURITY_CTX: add security context to create, mkdir, symlink, and
* mknod
* FUSE_HAS_INODE_DAX: use per inode DAX
+ * FUSE_WRITEBACK_CACHE_V2:
+ * - allow time/size to be refreshed if no pending write
+ * - time/size not cached for falocate/copy_file_range
*/
#define FUSE_ASYNC_READ (1 << 0)
#define FUSE_POSIX_LOCKS (1 << 1)
@@ -389,6 +393,7 @@ struct fuse_file_lock {
/* bits 32..63 get shifted down 32 bits into the flags2 field */
#define FUSE_SECURITY_CTX (1ULL << 32)
#define FUSE_HAS_INODE_DAX (1ULL << 33)
+#define FUSE_WRITEBACK_CACHE_V2 (1ULL << 34)

/**
* CUSE INIT request/reply flags
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -222,19 +222,37 @@ void fuse_change_attributes_common(struc
u32 fuse_get_cache_mask(struct inode *inode)
{
struct fuse_conn *fc = get_fuse_conn(inode);
+ struct fuse_inode *fi = get_fuse_inode(inode);

if (!fc->writeback_cache || !S_ISREG(inode->i_mode))
return 0;

+ /*
+ * In writeback_cache_v2 mode if all the following conditions are met,
+ * then allow the attributes to be refreshed:
+ *
+ * - inode is not dirty (I_DIRTY_INODE)
+ * - inode is not in the process of being written (I_SYNC)
+ * - inode has no dirty pages (I_DIRTY_PAGES)
+ * - inode does not have any page writeback in progress
+ *
+ * Note: checking PAGECACHE_TAG_WRITEBACK is not sufficient in fuse,
+ * since inode can appear to have no PageWriteback pages, yet still have
+ * outstanding write request.
+ */
+ if (fc->writeback_cache_v2 && !(inode->i_state & (I_DIRTY | I_SYNC)) &&
+ RB_EMPTY_ROOT(&fi->writepages))
+ return 0;
+
return STATX_MTIME | STATX_CTIME | STATX_SIZE;
}

-void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
- u64 attr_valid, u64 attr_version)
+void fuse_change_attributes_mask(struct inode *inode, struct fuse_attr *attr,
+ u64 attr_valid, u64 attr_version,
+ u32 cache_mask)
{
struct fuse_conn *fc = get_fuse_conn(inode);
struct fuse_inode *fi = get_fuse_inode(inode);
- u32 cache_mask;
loff_t oldsize;
struct timespec64 old_mtime;

@@ -244,7 +262,7 @@ void fuse_change_attributes(struct inode
* may update i_size. In these cases trust the cached value in the
* inode.
*/
- cache_mask = fuse_get_cache_mask(inode);
+ cache_mask |= fuse_get_cache_mask(inode);
if (cache_mask & STATX_SIZE)
attr->size = i_size_read(inode);

@@ -1153,6 +1171,10 @@ static void process_init_reply(struct fu
fc->async_dio = 1;
if (flags & FUSE_WRITEBACK_CACHE)
fc->writeback_cache = 1;
+ if (flags & FUSE_WRITEBACK_CACHE_V2) {
+ fc->writeback_cache = 1;
+ fc->writeback_cache_v2 = 1;
+ }
if (flags & FUSE_PARALLEL_DIROPS)
fc->parallel_dirops = 1;
if (flags & FUSE_HANDLE_KILLPRIV)
@@ -1234,7 +1256,7 @@ void fuse_send_init(struct fuse_mount *f
FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_INIT_EXT |
- FUSE_SECURITY_CTX;
+ FUSE_SECURITY_CTX | FUSE_WRITEBACK_CACHE_V2;
#ifdef CONFIG_FUSE_DAX
if (fm->fc->dax)
flags |= FUSE_MAP_ALIGNMENT;
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -213,6 +213,7 @@ static int fuse_dentry_revalidate(struct
FUSE_ARGS(args);
struct fuse_forget_link *forget;
u64 attr_version;
+ u32 cache_mask;

/* For negative dentries, always do a fresh lookup */
if (!inode)
@@ -230,6 +231,7 @@ static int fuse_dentry_revalidate(struct
goto out;

attr_version = fuse_get_attr_version(fm->fc);
+ cache_mask = fuse_get_cache_mask(inode);

parent = dget_parent(entry);
fuse_lookup_init(fm->fc, &args, get_node_id(d_inode(parent)),
@@ -259,9 +261,9 @@ static int fuse_dentry_revalidate(struct
goto invalid;

forget_all_cached_acls(inode);
- fuse_change_attributes(inode, &outarg.attr,
- entry_attr_timeout(&outarg),
- attr_version);
+ fuse_change_attributes_mask(inode, &outarg.attr,
+ entry_attr_timeout(&outarg),
+ attr_version, cache_mask);
fuse_change_entry_timeout(entry, &outarg);
} else if (inode) {
fi = get_fuse_inode(inode);
@@ -836,16 +838,23 @@ static int fuse_symlink(struct user_name

void fuse_flush_time_update(struct inode *inode)
{
- int err = sync_inode_metadata(inode, 1);
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ int err;

- mapping_set_error(inode->i_mapping, err);
+ if (!fc->writeback_cache_v2) {
+ err = sync_inode_metadata(inode, 1);
+ mapping_set_error(inode->i_mapping, err);
+ }
}

static void fuse_update_ctime_in_cache(struct inode *inode)
{
if (!IS_NOCMTIME(inode)) {
+ struct fuse_conn *fc = get_fuse_conn(inode);
+
inode->i_ctime = current_time(inode);
- mark_inode_dirty_sync(inode);
+ if (!fc->writeback_cache_v2)
+ mark_inode_dirty_sync(inode);
fuse_flush_time_update(inode);
}
}
@@ -1065,7 +1074,7 @@ static void fuse_fillattr(struct inode *
}

static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
- struct file *file)
+ struct file *file, u32 cache_mask)
{
int err;
struct fuse_getattr_in inarg;
@@ -1100,9 +1109,9 @@ static int fuse_do_getattr(struct inode
fuse_make_bad(inode);
err = -EIO;
} else {
- fuse_change_attributes(inode, &outarg.attr,
- attr_timeout(&outarg),
- attr_version);
+ fuse_change_attributes_mask(inode, &outarg.attr,
+ attr_timeout(&outarg),
+ attr_version, cache_mask);
if (stat)
fuse_fillattr(inode, &outarg.attr, stat);
}
@@ -1131,7 +1140,7 @@ static int fuse_update_get_attr(struct i

if (sync) {
forget_all_cached_acls(inode);
- err = fuse_do_getattr(inode, stat, file);
+ err = fuse_do_getattr(inode, stat, file, cache_mask);
} else if (stat) {
generic_fillattr(&init_user_ns, inode, stat);
stat->mode = fi->orig_i_mode;
@@ -1277,7 +1286,7 @@ static int fuse_perm_getattr(struct inod
return -ECHILD;

forget_all_cached_acls(inode);
- return fuse_do_getattr(inode, NULL, NULL);
+ return fuse_do_getattr(inode, NULL, NULL, 0);
}

/*
@@ -1833,7 +1842,7 @@ static int fuse_setattr(struct user_name
* ia_mode calculation may have used stale i_mode.
* Refresh and recalculate.
*/
- ret = fuse_do_getattr(inode, NULL, file);
+ ret = fuse_do_getattr(inode, NULL, file, 0);
if (ret)
return ret;

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2949,6 +2949,19 @@ static int fuse_writeback_range(struct i
return err;
}

+static void fuse_update_time(struct file *file)
+{
+ struct inode *inode = file_inode(file);
+ struct fuse_conn *fc = get_fuse_conn(inode);
+
+ if (!IS_NOCMTIME(inode)) {
+ if (fc->writeback_cache_v2)
+ inode->i_mtime = inode->i_ctime = current_time(inode);
+ else
+ file_update_time(file);
+ }
+}
+
static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
loff_t length)
{
@@ -3021,7 +3034,7 @@ static long fuse_file_fallocate(struct f
/* we could have extended the file */
if (!(mode & FALLOC_FL_KEEP_SIZE)) {
if (fuse_write_update_attr(inode, offset + length, length))
- file_update_time(file);
+ fuse_update_time(file);
}

if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
@@ -3135,7 +3148,7 @@ static ssize_t __fuse_copy_file_range(st
ALIGN_DOWN(pos_out, PAGE_SIZE),
ALIGN(pos_out + outarg.size, PAGE_SIZE) - 1);

- file_update_time(file_out);
+ fuse_update_time(file_out);
fuse_write_update_attr(inode_out, pos_out + outarg.size, outarg.size);

err = outarg.size;
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -654,6 +654,9 @@ struct fuse_conn {
/* show legacy mount options */
unsigned int legacy_opts_show:1;

+ /* Improved writeback cache policy */
+ unsigned writeback_cache_v2:1;
+
/*
* fs kills suid/sgid/cap on write/chown/trunc. suid is killed on
* write/trunc only if caller did not have CAP_FSETID. sgid is killed
@@ -1049,8 +1052,17 @@ void fuse_init_symlink(struct inode *ino
/**
* Change attributes of an inode
*/
+void fuse_change_attributes_mask(struct inode *inode, struct fuse_attr *attr,
+ u64 attr_valid, u64 attr_version,
+ u32 cache_mask);
+
+static inline
void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
- u64 attr_valid, u64 attr_version);
+ u64 attr_valid, u64 attr_version)
+{
+ return fuse_change_attributes_mask(inode, attr,
+ attr_valid, attr_version, 0);
+}

void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
u64 attr_valid, u32 cache_mask);

Next message: Martin K. Petersen: "Re: [PATCH] scsi: ufs: using pm_runtime_resume_and_get instead of pm_runtime_get_sync"
Previous message: Sandipan Das: "[PATCH v3 7/7] kvm: x86/cpuid: Fix CPUID leaf 0xA"
In reply to: Jiachen Zhang: "Re: Re: Re: [RFC PATCH] fuse: support cache revalidation in writeback_cache mode"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]