Re: [PATCH 2/4 v2] f2fs: support atomic_write feature for database

From: Jaegeuk Kim
Date: Tue Sep 30 2014 - 02:19:15 EST

Change log from v1:
o change data structures to fix race conditions

This patch introduces a very limited functionality for atomic write support.
In order to support atomic write, this patch adds two ioctls:
o F2FS_IOC_ATOMIC_WRITE
o F2FS_IOC_ATOMIC_COMMIT

For F2FS_IOC_ATOMIC_WRITE, this patch introduces a data structure to communicate
with applications.

struct atmoic_w {
u64 aid; /* atomic write id */
const char __user *buf; /* user data */
u64 count; /* size to update */
u64 pos; /* file offset */
};

This is almost same as write() system call, and application can easily submit
any atomic data by calling
f2fs_ioctl(fd, F2FS_IOC_ATOMIC_WRITE, struct atomic_w *);

Then, data's page indices are recorded in the linked list, atomic_range list.
Later, f2fs_ioctl(fd, F2FS_IOC_ATOMIC_COMMIT, aid) trigger will flush all the
previous atomic data to the storage, which will be shown all or nothing by
f2fs recovery procedure.

Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
fs/f2fs/data.c | 6 +++-
fs/f2fs/f2fs.h | 25 +++++++++++--
fs/f2fs/file.c | 55 ++++++++++++++++++++++++++++
fs/f2fs/inode.c | 4 +++
fs/f2fs/segment.c | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/f2fs/segment.h | 11 ++++--
fs/f2fs/super.c | 3 ++
7 files changed, 204 insertions(+), 6 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 13ab7208..c4f1f93 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -14,6 +14,7 @@
#include <linux/mpage.h>
#include <linux/aio.h>
#include <linux/writeback.h>
+#include <linux/mount.h>
#include <linux/backing-dev.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
@@ -1052,7 +1053,10 @@ static int f2fs_write_end(struct file *file,

trace_f2fs_write_end(inode, pos, len, copied);

- set_page_dirty(page);
+ if (is_inode_flag_set(F2FS_I(inode), FI_ATOMIC_FILE))
+ prepare_atomic_page(inode, page);
+ else
+ set_page_dirty(page);

if (pos + copied > i_size_read(inode)) {
i_size_write(inode, pos + copied);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index a397f7a..ca8aa76 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -192,8 +192,19 @@ static inline bool __has_cursum_space(struct f2fs_summary_block *sum, int size,
/*
* ioctl commands
*/
-#define F2FS_IOC_GETFLAGS FS_IOC_GETFLAGS
-#define F2FS_IOC_SETFLAGS FS_IOC_SETFLAGS
+#define F2FS_IOC_GETFLAGS FS_IOC_GETFLAGS
+#define F2FS_IOC_SETFLAGS FS_IOC_SETFLAGS
+
+#define F2FS_IOCTL_MAGIC 0xf5
+#define F2FS_IOC_ATOMIC_WRITE _IOW(F2FS_IOCTL_MAGIC, 1, struct atomic_w)
+#define F2FS_IOC_ATOMIC_COMMIT _IOW(F2FS_IOCTL_MAGIC, 2, u64)
+
+struct atomic_w {
+ u64 aid; /* atomic write id */
+ const char __user *buf; /* user data */
+ u64 count; /* size to update */
+ u64 pos; /* file offset */
+};

#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
/*
@@ -263,6 +274,10 @@ struct f2fs_inode_info {
unsigned long long xattr_ver; /* cp version of xattr modification */
struct extent_info ext; /* in-memory extent cache entry */
struct dir_inode_entry *dirty_dir; /* the pointer of dirty dir */
+
+ struct list_head atomic_pages; /* atomic page indexes */
+ spinlock_t atomic_lock; /* lock for atomic pages */
+ struct radix_tree_root atomic_root; /* root of the atomic pages */
};

static inline void get_extent_info(struct extent_info *ext,
@@ -1051,7 +1066,8 @@ enum {
FI_INLINE_DATA, /* used for inline data*/
FI_APPEND_WRITE, /* inode has appended data */
FI_UPDATE_WRITE, /* inode has in-place-update data */
- FI_NEED_IPU, /* used fo ipu for fdatasync */
+ FI_NEED_IPU, /* used for ipu for fdatasync */
+ FI_ATOMIC_FILE, /* used for atomic writes support */
};

static inline void set_inode_flag(struct f2fs_inode_info *fi, int flag)
@@ -1275,6 +1291,9 @@ void destroy_node_manager_caches(void);
/*
* segment.c
*/
+void register_atomic_pages(struct inode *, struct atomic_w *);
+void prepare_atomic_page(struct inode *, struct page *);
+void commit_atomic_pages(struct inode *, u64, bool);
void f2fs_balance_fs(struct f2fs_sb_info *);
void f2fs_balance_fs_bg(struct f2fs_sb_info *);
int f2fs_issue_flush(struct f2fs_sb_info *);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 735e9a2..a5a0bc7 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -862,6 +862,57 @@ out:
return ret;
}

+static int f2fs_ioc_atomic_write(struct file *filp, unsigned long arg)
+{
+ struct inode *inode = file_inode(filp);
+ struct atomic_w aw;
+ loff_t pos;
+ int ret;
+
+ if (!inode_owner_or_capable(inode))
+ return -EACCES;
+
+ if (copy_from_user(&aw, (struct atomic_w __user *)arg, sizeof(aw)))
+ return -EFAULT;
+
+ ret = mnt_want_write_file(filp);
+ if (ret)
+ return ret;
+
+ pos = aw.pos;
+ set_inode_flag(F2FS_I(inode), FI_ATOMIC_FILE);
+ ret = vfs_write(filp, aw.buf, aw.count, &pos);
+ if (ret >= 0)
+ register_atomic_pages(inode, &aw);
+ else
+ clear_inode_flag(F2FS_I(inode), FI_ATOMIC_FILE);
+
+ mnt_drop_write_file(filp);
+ return ret;
+}
+
+static int f2fs_ioc_atomic_commit(struct file *filp, unsigned long arg)
+{
+ struct inode *inode = file_inode(filp);
+ int ret;
+ u64 aid;
+
+ if (!inode_owner_or_capable(inode))
+ return -EACCES;
+
+ if (copy_from_user(&aid, (u64 __user *)arg, sizeof(u64)))
+ return -EFAULT;
+
+ ret = mnt_want_write_file(filp);
+ if (ret)
+ return ret;
+
+ commit_atomic_pages(inode, aid, false);
+ ret = f2fs_sync_file(filp, 0, LONG_MAX, 0);
+ mnt_drop_write_file(filp);
+ return ret;
+}
+
static int f2fs_ioc_fitrim(struct file *filp, unsigned long arg)
{
struct inode *inode = file_inode(filp);
@@ -899,6 +950,10 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return f2fs_ioc_getflags(filp, arg);
case F2FS_IOC_SETFLAGS:
return f2fs_ioc_setflags(filp, arg);
+ case F2FS_IOC_ATOMIC_WRITE:
+ return f2fs_ioc_atomic_write(filp, arg);
+ case F2FS_IOC_ATOMIC_COMMIT:
+ return f2fs_ioc_atomic_commit(filp, arg);
case FITRIM:
return f2fs_ioc_fitrim(filp, arg);
default:
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 63923ee..002036b 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -269,6 +269,10 @@ void f2fs_evict_inode(struct inode *inode)
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
nid_t xnid = F2FS_I(inode)->i_xattr_nid;

+ /* some remained atomic pages should discarded */
+ if (is_inode_flag_set(F2FS_I(inode), FI_ATOMIC_FILE))
+ commit_atomic_pages(inode, 0, true);
+
trace_f2fs_evict_inode(inode);
truncate_inode_pages_final(&inode->i_data);

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index d30cd16..a7cc250 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -26,6 +26,7 @@

static struct kmem_cache *discard_entry_slab;
static struct kmem_cache *sit_entry_set_slab;
+static struct kmem_cache *aw_entry_slab;

/*
* __reverse_ffs is copied from include/asm-generic/bitops/__ffs.h since
@@ -173,6 +174,104 @@ found_middle:
return result + __reverse_ffz(tmp);
}

+/* For atomic write support */
+void register_atomic_pages(struct inode *inode, struct atomic_w *aw)
+{
+ pgoff_t start = aw->pos >> PAGE_CACHE_SHIFT;
+ pgoff_t end = (aw->pos + aw->count + PAGE_CACHE_SIZE - 1) >>
+ PAGE_CACHE_SHIFT;
+ struct atomic_pages *cur;
+
+ spin_lock(&F2FS_I(inode)->atomic_lock);
+ list_for_each_entry(cur, &F2FS_I(inode)->atomic_pages, list)
+ if (cur->aid == (u64)current->pid &&
+ start <= cur->page->index &&
+ cur->page->index < end)
+ cur->aid = aw->aid;
+ spin_unlock(&F2FS_I(inode)->atomic_lock);
+}
+
+void prepare_atomic_page(struct inode *inode, struct page *page)
+{
+ struct f2fs_inode_info *fi = F2FS_I(inode);
+ struct atomic_pages *new;
+ int err;
+retry:
+ new = f2fs_kmem_cache_alloc(aw_entry_slab, GFP_NOFS);
+
+ /* add atomic page indices to the list */
+ new->aid = (u64)current->pid;
+ new->page = page;
+ get_page(page);
+ INIT_LIST_HEAD(&new->list);
+
+ /* increase reference count with clean state */
+ spin_lock(&fi->atomic_lock);
+ err = radix_tree_insert(&fi->atomic_root, page->index, new);
+ if (err == -EEXIST) {
+ f2fs_put_page(page, 0);
+ spin_unlock(&fi->atomic_lock);
+ kmem_cache_free(aw_entry_slab, new);
+ return;
+ } else if (err) {
+ spin_unlock(&fi->atomic_lock);
+ kmem_cache_free(aw_entry_slab, new);
+ goto retry;
+ }
+ list_add_tail(&new->list, &fi->atomic_pages);
+ spin_unlock(&fi->atomic_lock);
+}
+
+void commit_atomic_pages(struct inode *inode, u64 aid, bool abort)
+{
+ struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+ struct f2fs_inode_info *fi = F2FS_I(inode);
+ struct atomic_pages *cur, *tmp;
+ LIST_HEAD(target);
+ struct f2fs_io_info fio = {
+ .type = DATA,
+ .rw = WRITE_SYNC,
+ };
+
+ /* Step #1: move the pages to a temp list */
+ spin_lock(&fi->atomic_lock);
+ list_for_each_entry_safe(cur, tmp, &fi->atomic_pages, list) {
+ if (!abort && cur->aid != aid)
+ continue;
+ radix_tree_delete(&fi->atomic_root, cur->page->index);
+ list_move_tail(&cur->list, &target);
+ }
+ spin_unlock(&fi->atomic_lock);
+
+ if (abort)
+ goto release;
+
+ f2fs_balance_fs(sbi);
+ f2fs_lock_op(sbi);
+
+ /* Step #2: write all the pages */
+ list_for_each_entry(cur, &target, list) {
+ lock_page(cur->page);
+ f2fs_wait_on_page_writeback(cur->page, DATA);
+ if (clear_page_dirty_for_io(cur->page))
+ inode_dec_dirty_pages(inode);
+ do_write_data_page(cur->page, &fio);
+ unlock_page(cur->page);
+ }
+ f2fs_submit_merged_bio(sbi, DATA, WRITE);
+ f2fs_unlock_op(sbi);
+release:
+ /* Step #3: wait for writeback */
+ list_for_each_entry_safe(cur, tmp, &target, list) {
+ wait_on_page_writeback(cur->page);
+
+ /* release reference got by atomic_write operation */
+ f2fs_put_page(cur->page, 0);
+ list_del(&cur->list);
+ kmem_cache_free(aw_entry_slab, cur);
+ }
+}
+
/*
* This function balances dirty node and dentry pages.
* In addition, it controls garbage collection.
@@ -2153,8 +2252,14 @@ int __init create_segment_manager_caches(void)
sizeof(struct nat_entry_set));
if (!sit_entry_set_slab)
goto destory_discard_entry;
+ aw_entry_slab = f2fs_kmem_cache_create("atomic_entry",
+ sizeof(struct atomic_pages));
+ if (!aw_entry_slab)
+ goto destroy_sit_entry_set;
return 0;

+destroy_sit_entry_set:
+ kmem_cache_destroy(sit_entry_set_slab);
destory_discard_entry:
kmem_cache_destroy(discard_entry_slab);
fail:
@@ -2165,4 +2270,5 @@ void destroy_segment_manager_caches(void)
{
kmem_cache_destroy(sit_entry_set_slab);
kmem_cache_destroy(discard_entry_slab);
+ kmem_cache_destroy(aw_entry_slab);
}
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index d372dbf..5b68810 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -175,6 +175,12 @@ struct segment_allocation {
void (*allocate_segment)(struct f2fs_sb_info *, int, bool);
};

+struct atomic_pages {
+ struct list_head list;
+ u64 aid;
+ struct page *page;
+};
+
struct sit_info {
const struct segment_allocation *s_ops;

@@ -502,9 +508,10 @@ static inline bool need_inplace_update(struct inode *inode)
{
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
unsigned int policy = SM_I(sbi)->ipu_policy;
+ struct f2fs_inode_info *fi = F2FS_I(inode);

/* IPU can be done only for the user data */
- if (S_ISDIR(inode->i_mode))
+ if (S_ISDIR(inode->i_mode) || is_inode_flag_set(fi, FI_ATOMIC_FILE))
return false;

if (policy & (0x1 << F2FS_IPU_FORCE))
@@ -520,7 +527,7 @@ static inline bool need_inplace_update(struct inode *inode)

/* this is only set during fdatasync */
if (policy & (0x1 << F2FS_IPU_FSYNC) &&
- is_inode_flag_set(F2FS_I(inode), FI_NEED_IPU))
+ is_inode_flag_set(fi, FI_NEED_IPU))
return true;

return false;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index bb6b568..dbadfd2 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -373,6 +373,9 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
fi->i_advise = 0;
rwlock_init(&fi->ext.ext_lock);
init_rwsem(&fi->i_sem);
+ INIT_LIST_HEAD(&fi->atomic_pages);
+ spin_lock_init(&fi->atomic_lock);
+ INIT_RADIX_TREE(&fi->atomic_root, GFP_ATOMIC);

set_inode_flag(fi, FI_NEW_INODE);

--
2.1.1

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