Re: [PATCH 09/18] f2fs: use generic posix ACL infrastructure

Jaegeuk Kim
2013-12-08T23:30:02Z

2013-12-08 (일), 01:14 -0800, Christoph Hellwig:
> On Fri, Dec 06, 2013 at 10:37:34AM +0900, Jaegeuk Kim wrote:
> > f2fs caches a new mode bit for a while to make the consistency between
> > xattr's acl mode and the inode mode.
>
> Can you explain what exactly you're trying to do there? I've been
> trying to unwrap what's going on and can't really see the point:
>
> - i_acl_mode and FI_ACL_MODE get set in __setattr_copy, but right
> after that call, still under i_mutex and before marking the inode
> dirty f2fs_acl_chmod makes use of it, and it gets cleared right
> after. Is there any race that could happen with a locked inode
> not marked dirty yet on f2fs?

As you guess, there is no race problem, but the problem is on acl
consistency between xattr->mode and inode->mode.

Previously, f2fs_setattr triggers:
new_mode inode->mode xattr->mode iblock->mode
f2fs_setattr x -> x y y
[update_inode] x --- [ y ] ---> x
[checkpoint] x y x
__f2fs_setxattr x -> x x

In this flow, f2fs is able to break the consistency between xattr->mode
and iblock->mode after checkpoint followed by sudden-power-off.

So, fi->mode was introduced to address the problem.
The new f2fs_setattr triggers:
new_mode inode->mode fi->mode xattr->mode iblock->mode
f2fs_setattr x --- [y] ---> x y y
[update_inode] y x y y
[checkpoint] y x y y
__f2fs_setxattr x <- x -> x -> x

Finally, __f2fs_setxattr synchronizes inode->mode, xattr->mode, and
iblock->mode all together.

The root question is "is it possible to call update_inode in the
i_mutex-covered region like f2fs_setattr?".
The update_inode of f2fs is called from a bunch of places so currently
I'm not sure it can be impossible.

Thanks,

> We could pass a mode argument
> to posix_acl_create, but I'd prefer to avoid that if we can.
> - on the set_acl side it gets set in __f2fs_set_acl, and then
> i_mode is update in __f2fs_setxattr which could easily done with
> a stack variable.
>
> RFC patch below:
>
>
> diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
> index 4f52fe0f..6647545 100644
> --- a/fs/f2fs/acl.c
> +++ b/fs/f2fs/acl.c
> @@ -17,9 +17,6 @@
> #include "xattr.h"
> #include "acl.h"
>
> -#define get_inode_mode(i) ((is_inode_flag_set(F2FS_I(i), FI_ACL_MODE)) ? \
> - (F2FS_I(i)->i_acl_mode) : ((i)->i_mode))
> -
> static inline size_t f2fs_acl_size(int count)
> {
> if (count <= 4) {
> @@ -209,11 +206,11 @@ static int __f2fs_set_acl(struct inode *inode, int type,
> struct posix_acl *acl, struct page *ipage)
> {
> struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
> - struct f2fs_inode_info *fi = F2FS_I(inode);
> int name_index;
> void *value = NULL;
> size_t size = 0;
> int error;
> + umode_t mode = 0;
>
> if (!test_opt(sbi, POSIX_ACL))
> return 0;
> @@ -224,10 +221,10 @@ static int __f2fs_set_acl(struct inode *inode, int type,
> case ACL_TYPE_ACCESS:
> name_index = F2FS_XATTR_INDEX_POSIX_ACL_ACCESS;
> if (acl) {
> - error = posix_acl_equiv_mode(acl, &inode->i_mode);
> + mode = inode->i_mode;
> + error = posix_acl_equiv_mode(acl, &mode);
> if (error < 0)
> return error;
> - set_acl_inode(fi, inode->i_mode);
> if (error == 0)
> acl = NULL;
> }
> @@ -245,19 +242,15 @@ static int __f2fs_set_acl(struct inode *inode, int type,
>
> if (acl) {
> value = f2fs_acl_to_disk(acl, &size);
> - if (IS_ERR(value)) {
> - cond_clear_inode_flag(fi, FI_ACL_MODE);
> + if (IS_ERR(value))
> return (int)PTR_ERR(value);
> - }
> }
>
> - error = f2fs_setxattr(inode, name_index, "", value, size, ipage);
> + error = f2fs_setxattr(inode, name_index, "", value, size, ipage, mode);
>
> kfree(value);
> if (!error)
> set_cached_acl(inode, type, acl);
> -
> - cond_clear_inode_flag(fi, FI_ACL_MODE);
> return error;
> }
>
> @@ -289,28 +282,3 @@ int f2fs_init_acl(struct inode *inode, struct inode *dir, struct page *ipage)
>
> return error;
> }
> -
> -int f2fs_acl_chmod(struct inode *inode)
> -{
> - struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
> - struct posix_acl *acl;
> - int error;
> - umode_t mode = get_inode_mode(inode);
> -
> - if (!test_opt(sbi, POSIX_ACL))
> - return 0;
> - if (S_ISLNK(mode))
> - return -EOPNOTSUPP;
> -
> - acl = f2fs_get_acl(inode, ACL_TYPE_ACCESS);
> - if (IS_ERR(acl) || !acl)
> - return PTR_ERR(acl);
> -
> - error = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
> - if (error)
> - return error;
> -
> - error = __f2fs_set_acl(inode, ACL_TYPE_ACCESS, acl, NULL);
> - posix_acl_release(acl);
> - return error;
> -}
> diff --git a/fs/f2fs/acl.h b/fs/f2fs/acl.h
> index 2af31fe..e086465 100644
> --- a/fs/f2fs/acl.h
> +++ b/fs/f2fs/acl.h
> @@ -38,18 +38,12 @@ struct f2fs_acl_header {
>
> extern struct posix_acl *f2fs_get_acl(struct inode *, int);
> extern int f2fs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
> -extern int f2fs_acl_chmod(struct inode *);
> extern int f2fs_init_acl(struct inode *, struct inode *, struct page *);
> #else
> #define f2fs_check_acl NULL
> #define f2fs_get_acl NULL
> #define f2fs_set_acl NULL
>
> -static inline int f2fs_acl_chmod(struct inode *inode)
> -{
> - return 0;
> -}
> -
> static inline int f2fs_init_acl(struct inode *inode, struct inode *dir,
> struct page *page)
> {
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 89dc750..1e774e6 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -181,7 +181,6 @@ struct f2fs_inode_info {
> unsigned char i_advise; /* use to give file attribute hints */
> unsigned int i_current_depth; /* use only in directory structure */
> unsigned int i_pino; /* parent inode number */
> - umode_t i_acl_mode; /* keep file acl mode temporarily */
>
> /* Use below internally in f2fs*/
> unsigned long flags; /* use to pass per-file flags */
> @@ -872,7 +871,6 @@ enum {
> FI_NEW_INODE, /* indicate newly allocated inode */
> FI_DIRTY_INODE, /* indicate inode is dirty or not */
> FI_INC_LINK, /* need to increment i_nlink */
> - FI_ACL_MODE, /* indicate acl mode */
> FI_NO_ALLOC, /* should not allocate any blocks */
> FI_UPDATE_DIR, /* should update inode block for consistency */
> FI_DELAY_IPUT, /* used for the recovery */
> @@ -894,21 +892,6 @@ static inline void clear_inode_flag(struct f2fs_inode_info *fi, int flag)
> clear_bit(flag, &fi->flags);
> }
>
> -static inline void set_acl_inode(struct f2fs_inode_info *fi, umode_t mode)
> -{
> - fi->i_acl_mode = mode;
> - set_inode_flag(fi, FI_ACL_MODE);
> -}
> -
> -static inline int cond_clear_inode_flag(struct f2fs_inode_info *fi, int flag)
> -{
> - if (is_inode_flag_set(fi, FI_ACL_MODE)) {
> - clear_inode_flag(fi, FI_ACL_MODE);
> - return 1;
> - }
> - return 0;
> -}
> -
> static inline void get_inline_info(struct f2fs_inode_info *fi,
> struct f2fs_inode *ri)
> {
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 13eff60..80ef669 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -339,41 +339,9 @@ int f2fs_getattr(struct vfsmount *mnt,
> return 0;
> }
>
> -#ifdef CONFIG_F2FS_FS_POSIX_ACL
> -static void __setattr_copy(struct inode *inode, const struct iattr *attr)
> -{
> - struct f2fs_inode_info *fi = F2FS_I(inode);
> - unsigned int ia_valid = attr->ia_valid;
> -
> - if (ia_valid & ATTR_UID)
> - inode->i_uid = attr->ia_uid;
> - if (ia_valid & ATTR_GID)
> - inode->i_gid = attr->ia_gid;
> - if (ia_valid & ATTR_ATIME)
> - inode->i_atime = timespec_trunc(attr->ia_atime,
> - inode->i_sb->s_time_gran);
> - if (ia_valid & ATTR_MTIME)
> - inode->i_mtime = timespec_trunc(attr->ia_mtime,
> - inode->i_sb->s_time_gran);
> - if (ia_valid & ATTR_CTIME)
> - inode->i_ctime = timespec_trunc(attr->ia_ctime,
> - inode->i_sb->s_time_gran);
> - if (ia_valid & ATTR_MODE) {
> - umode_t mode = attr->ia_mode;
> -
> - if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
> - mode &= ~S_ISGID;
> - set_acl_inode(fi, mode);
> - }
> -}
> -#else
> -#define __setattr_copy setattr_copy
> -#endif
> -
> int f2fs_setattr(struct dentry *dentry, struct iattr *attr)
> {
> struct inode *inode = dentry->d_inode;
> - struct f2fs_inode_info *fi = F2FS_I(inode);
> int err;
>
> err = inode_change_ok(inode, attr);
> @@ -387,15 +355,9 @@ int f2fs_setattr(struct dentry *dentry, struct iattr *attr)
> f2fs_balance_fs(F2FS_SB(inode->i_sb));
> }
>
> - __setattr_copy(inode, attr);
> -
> - if (attr->ia_valid & ATTR_MODE) {
> - err = f2fs_acl_chmod(inode);
> - if (err || is_inode_flag_set(fi, FI_ACL_MODE)) {
> - inode->i_mode = fi->i_acl_mode;
> - clear_inode_flag(fi, FI_ACL_MODE);
> - }
> - }
> + setattr_copy(inode, attr);
> + if (attr->ia_valid & ATTR_MODE)
> + err = posix_acl_chmod(inode);
>
> mark_inode_dirty(inode);
> return err;
> diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
> index e2b9299..8820857 100644
> --- a/fs/f2fs/xattr.c
> +++ b/fs/f2fs/xattr.c
> @@ -108,7 +108,7 @@ static int f2fs_xattr_generic_set(struct dentry *dentry, const char *name,
> if (strcmp(name, "") == 0)
> return -EINVAL;
>
> - return f2fs_setxattr(dentry->d_inode, type, name, value, size, NULL);
> + return f2fs_setxattr(dentry->d_inode, type, name, value, size, NULL, 0);
> }
>
> static size_t f2fs_xattr_advise_list(struct dentry *dentry, char *list,
> @@ -157,7 +157,7 @@ static int f2fs_xattr_advise_set(struct dentry *dentry, const char *name,
> #ifdef CONFIG_F2FS_FS_SECURITY
> static int __f2fs_setxattr(struct inode *inode, int name_index,
> const char *name, const void *value, size_t value_len,
> - struct page *ipage);
> + struct page *ipage, umode_t mode);
> static int f2fs_initxattrs(struct inode *inode, const struct xattr *xattr_array,
> void *page)
> {
> @@ -167,7 +167,7 @@ static int f2fs_initxattrs(struct inode *inode, const struct xattr *xattr_array,
> for (xattr = xattr_array; xattr->name != NULL; xattr++) {
> err = __f2fs_setxattr(inode, F2FS_XATTR_INDEX_SECURITY,
> xattr->name, xattr->value,
> - xattr->value_len, (struct page *)page);
> + xattr->value_len, (struct page *)page, 0);
> if (err < 0)
> break;
> }
> @@ -475,9 +475,8 @@ cleanup:
>
> static int __f2fs_setxattr(struct inode *inode, int name_index,
> const char *name, const void *value, size_t value_len,
> - struct page *ipage)
> + struct page *ipage, umode_t mode)
> {
> - struct f2fs_inode_info *fi = F2FS_I(inode);
> struct f2fs_xattr_entry *here, *last;
> void *base_addr;
> int found, newsize;
> @@ -566,10 +565,9 @@ static int __f2fs_setxattr(struct inode *inode, int name_index,
> if (error)
> goto exit;
>
> - if (is_inode_flag_set(fi, FI_ACL_MODE)) {
> - inode->i_mode = fi->i_acl_mode;
> + if (mode) {
> + inode->i_mode = mode;
> inode->i_ctime = CURRENT_TIME;
> - clear_inode_flag(fi, FI_ACL_MODE);
> }
>
> if (ipage)
> @@ -582,7 +580,8 @@ exit:
> }
>
> int f2fs_setxattr(struct inode *inode, int name_index, const char *name,
> - const void *value, size_t value_len, struct page *ipage)
> + const void *value, size_t value_len, struct page *ipage,
> + umode_t mode)
> {
> struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
> int err;
> @@ -590,7 +589,8 @@ int f2fs_setxattr(struct inode *inode, int name_index, const char *name,
> f2fs_balance_fs(sbi);
>
> f2fs_lock_op(sbi);
> - err = __f2fs_setxattr(inode, name_index, name, value, value_len, ipage);
> + err = __f2fs_setxattr(inode, name_index, name, value, value_len, ipage,
> + mode);
> f2fs_unlock_op(sbi);
>
> return err;
> diff --git a/fs/f2fs/xattr.h b/fs/f2fs/xattr.h
> index b21d9eb..c73588a 100644
> --- a/fs/f2fs/xattr.h
> +++ b/fs/f2fs/xattr.h
> @@ -114,14 +114,15 @@ extern const struct xattr_handler f2fs_xattr_security_handler;
> extern const struct xattr_handler *f2fs_xattr_handlers[];
>
> extern int f2fs_setxattr(struct inode *, int, const char *,
> - const void *, size_t, struct page *);
> + const void *, size_t, struct page *, umode_t);
> extern int f2fs_getxattr(struct inode *, int, const char *, void *, size_t);
> extern ssize_t f2fs_listxattr(struct dentry *, char *, size_t);
> #else
>
> #define f2fs_xattr_handlers NULL
> static inline int f2fs_setxattr(struct inode *inode, int name_index,
> - const char *name, const void *value, size_t value_len)
> + const char *name, const void *value, size_t value_len,
> + umode_t mode)
> {
> return -EOPNOTSUPP;
> }
>
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--
Jaegeuk Kim
Samsung