Re: [f2fs-dev] [PATCH] f2fs: remove i_xattr_sem to avoid deadlock and fix the original issue
From: Chao Yu
Date: Sun Jun 25 2023 - 03:26:56 EST
On 2023/6/14 7:39, Jaegeuk Kim wrote:
This reverts commit 27161f13e3c3 "f2fs: avoid race in between read xattr & write xattr".
That introduced a deadlock case:
Thread #1:
[122554.641906][ T92] f2fs_getxattr+0xd4/0x5fc
-> waiting for f2fs_down_read(&F2FS_I(inode)->i_xattr_sem);
[122554.641927][ T92] __f2fs_get_acl+0x50/0x284
[122554.641948][ T92] f2fs_init_acl+0x84/0x54c
[122554.641969][ T92] f2fs_init_inode_metadata+0x460/0x5f0
[122554.641990][ T92] f2fs_add_inline_entry+0x11c/0x350
-> Locked dir->inode_page by f2fs_get_node_page()
[122554.642009][ T92] f2fs_do_add_link+0x100/0x1e4
[122554.642025][ T92] f2fs_create+0xf4/0x22c
[122554.642047][ T92] vfs_create+0x130/0x1f4
Thread #2:
[123996.386358][ T92] __get_node_page+0x8c/0x504
-> waiting for dir->inode_page lock
[123996.386383][ T92] read_all_xattrs+0x11c/0x1f4
[123996.386405][ T92] __f2fs_setxattr+0xcc/0x528
[123996.386424][ T92] f2fs_setxattr+0x158/0x1f4
-> f2fs_down_write(&F2FS_I(inode)->i_xattr_sem);
[123996.386443][ T92] __f2fs_set_acl+0x328/0x430
[123996.386618][ T92] f2fs_set_acl+0x38/0x50
[123996.386642][ T92] posix_acl_chmod+0xc8/0x1c8
[123996.386669][ T92] f2fs_setattr+0x5e0/0x6bc
[123996.386689][ T92] notify_change+0x4d8/0x580
[123996.386717][ T92] chmod_common+0xd8/0x184
[123996.386748][ T92] do_fchmodat+0x60/0x124
[123996.386766][ T92] __arm64_sys_fchmodat+0x28/0x3c
Let's take a look at the original issue back.
Thread A: Thread B:
-f2fs_getxattr
-lookup_all_xattrs
-xnid = F2FS_I(inode)->i_xattr_nid;
-f2fs_setxattr
-__f2fs_setxattr
-write_all_xattrs
-truncate_xattr_node
... ...
-write_checkpoint
... ...
-alloc_nid <- nid reuse
-get_node_page
-f2fs_bug_on <- nid != node_footer->nid
One concern below:
Thread A: Thread B:
- f2fs_getxattr
- lookup_all_xattrs
- read_inline_xattr
- f2fs_get_node_page(ino)
- memcpy inline xattr
- f2fs_put_page
- f2fs_setxattr
- __f2fs_setxattr
- __f2fs_setxattr
- write_all_xattrs
- write xnode and inode
---> inline xattr may out of update here.
- read_xattr_block
- f2fs_get_node_page(xnid)
- memcpy xnode xattr
- f2fs_put_page
Do we need to keep xattr_{get,set} being atomical operation?
Thanks,
I think we don't need to truncate xattr pages eagerly which introduces lots of
data races without big benefits.
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
fs/f2fs/f2fs.h | 1 -
fs/f2fs/super.c | 1 -
fs/f2fs/xattr.c | 31 ++++++++-----------------------
3 files changed, 8 insertions(+), 25 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 3f5b161dd743..7b9af2d51656 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -838,7 +838,6 @@ struct f2fs_inode_info {
/* avoid racing between foreground op and gc */
struct f2fs_rwsem i_gc_rwsem[2];
- struct f2fs_rwsem i_xattr_sem; /* avoid racing between reading and changing EAs */
int i_extra_isize; /* size of extra space located in i_addr */
kprojid_t i_projid; /* id for project quota */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 1b2c788ed80d..c917fa771f0e 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1418,7 +1418,6 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
INIT_LIST_HEAD(&fi->gdirty_list);
init_f2fs_rwsem(&fi->i_gc_rwsem[READ]);
init_f2fs_rwsem(&fi->i_gc_rwsem[WRITE]);
- init_f2fs_rwsem(&fi->i_xattr_sem);
/* Will be used by directory only */
fi->i_dir_level = F2FS_SB(sb)->dir_level;
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index 213805d3592c..bdc8a55085a2 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -433,7 +433,7 @@ static inline int write_all_xattrs(struct inode *inode, __u32 hsize,
{
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
size_t inline_size = inline_xattr_size(inode);
- struct page *in_page = NULL;
+ struct page *in_page = ipage;
void *xattr_addr;
void *inline_addr = NULL;
struct page *xpage;
@@ -446,29 +446,19 @@ static inline int write_all_xattrs(struct inode *inode, __u32 hsize,
/* write to inline xattr */
if (inline_size) {
- if (ipage) {
- inline_addr = inline_xattr_addr(inode, ipage);
- } else {
+ if (!in_page) {
in_page = f2fs_get_node_page(sbi, inode->i_ino);
if (IS_ERR(in_page)) {
f2fs_alloc_nid_failed(sbi, new_nid);
return PTR_ERR(in_page);
}
- inline_addr = inline_xattr_addr(inode, in_page);
}
+ inline_addr = inline_xattr_addr(inode, in_page);
- f2fs_wait_on_page_writeback(ipage ? ipage : in_page,
- NODE, true, true);
- /* no need to use xattr node block */
+ f2fs_wait_on_page_writeback(in_page, NODE, true, true);
if (hsize <= inline_size) {
- err = f2fs_truncate_xattr_node(inode);
- f2fs_alloc_nid_failed(sbi, new_nid);
- if (err) {
- f2fs_put_page(in_page, 1);
- return err;
- }
memcpy(inline_addr, txattr_addr, inline_size);
- set_page_dirty(ipage ? ipage : in_page);
+ set_page_dirty(in_page);
goto in_page_out;
}
}
@@ -502,12 +492,13 @@ static inline int write_all_xattrs(struct inode *inode, __u32 hsize,
memcpy(xattr_addr, txattr_addr + inline_size, VALID_XATTR_BLOCK_SIZE);
if (inline_size)
- set_page_dirty(ipage ? ipage : in_page);
+ set_page_dirty(in_page);
set_page_dirty(xpage);
f2fs_put_page(xpage, 1);
in_page_out:
- f2fs_put_page(in_page, 1);
+ if (in_page != ipage)
+ f2fs_put_page(in_page, 1);
return err;
}
@@ -528,10 +519,8 @@ int f2fs_getxattr(struct inode *inode, int index, const char *name,
if (len > F2FS_NAME_LEN)
return -ERANGE;
- f2fs_down_read(&F2FS_I(inode)->i_xattr_sem);
error = lookup_all_xattrs(inode, ipage, index, len, name,
&entry, &base_addr, &base_size, &is_inline);
- f2fs_up_read(&F2FS_I(inode)->i_xattr_sem);
if (error)
return error;
@@ -565,9 +554,7 @@ ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
int error;
size_t rest = buffer_size;
- f2fs_down_read(&F2FS_I(inode)->i_xattr_sem);
error = read_all_xattrs(inode, NULL, &base_addr);
- f2fs_up_read(&F2FS_I(inode)->i_xattr_sem);
if (error)
return error;
@@ -794,9 +781,7 @@ int f2fs_setxattr(struct inode *inode, int index, const char *name,
f2fs_balance_fs(sbi, true);
f2fs_lock_op(sbi);
- f2fs_down_write(&F2FS_I(inode)->i_xattr_sem);
err = __f2fs_setxattr(inode, index, name, value, size, ipage, flags);
- f2fs_up_write(&F2FS_I(inode)->i_xattr_sem);
f2fs_unlock_op(sbi);
f2fs_update_time(sbi, REQ_TIME);