| Message ID | 20230811033857.1800578-2-yebin10@huawei.com |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | fix race between setxattr and write back | expand |
On Fri 11-08-23 11:38:56, Ye Bin wrote: > There's a issue as follows: > Block Allocation Reservation Windows Map (ext2_try_to_allocate_with_rsv): > reservation window 0x000000006f105382 start: 0, end: 0 > reservation window 0x000000008fd1a555 start: 1044, end: 1059 > Window map complete. > kernel BUG at fs/ext2/balloc.c:1158! > invalid opcode: 0000 [#1] PREEMPT SMP KASAN > RIP: 0010:ext2_try_to_allocate_with_rsv.isra.0+0x15c4/0x1800 > Call Trace: > <TASK> > ext2_new_blocks+0x935/0x1690 > ext2_new_block+0x73/0xa0 > ext2_xattr_set2+0x74f/0x1730 > ext2_xattr_set+0x12b6/0x2260 > ext2_xattr_user_set+0x9c/0x110 > __vfs_setxattr+0x139/0x1d0 > __vfs_setxattr_noperm+0xfc/0x370 > __vfs_setxattr_locked+0x205/0x2c0 > vfs_setxattr+0x19d/0x3b0 > do_setxattr+0xff/0x220 > setxattr+0x123/0x150 > path_setxattr+0x193/0x1e0 > __x64_sys_setxattr+0xc8/0x170 > do_syscall_64+0x35/0x80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Above issue may happens as follows: > setxattr write back > ext2_xattr_set > ext2_xattr_set2 > ext2_new_block > ext2_new_blocks > ext2_try_to_allocate_with_rsv > alloc_new_reservation > --> group=0 [0, 1023] rsv [1016, 1023] > do_writepages > mpage_writepages > write_cache_pages > __mpage_writepage > ext2_get_block > ext2_get_blocks > ext2_alloc_branch > ext2_new_blocks > ext2_try_to_allocate_with_rsv > alloc_new_reservation > -->group=1 [1024, 2047] rsv [1044, 1059] > if ((my_rsv->rsv_start > group_last_block) || > (my_rsv->rsv_end < group_first_block) > rsv_window_dump > BUG(); > Now ext2 mkwrite delay allocate new blocks. So there maybe allocate blocks when > do write back. However, there is no concurrent protection between > ext2_xattr_set() and do_writepages(). > To solve about issue hold '&ei->truncate_mutex' lock when new block for xattr. > > Signed-off-by: Ye Bin <yebin10@huawei.com> Thanks for the patch! I agree the handling of reservation window and its use for block allocation needs to be protected by ei->i_truncate_mutex. However in this particular case of xattr allocation where we want to allocate just one block which is completely independent of file data, I'd rather choose to make ext2_new_blocks() ignore the reservation window (set my_rsv to NULL). There's already a logic at the beginning of ext2_new_blocks() deciding whether to use the reservation window or not and we could extend it - probably by adding flags argument to it a introducing a NORESERVE flag. Also as a preparatory patch, I'd just remove ext2_new_block() and opencode it in the xattr code since it has only that one user anyway. Honza > --- > fs/ext2/balloc.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c > index c8049c90323d..039f655febfd 100644 > --- a/fs/ext2/balloc.c > +++ b/fs/ext2/balloc.c > @@ -1432,8 +1432,14 @@ ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal, > ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp) > { > unsigned long count = 1; > + struct ext2_inode_info *ei = EXT2_I(inode); > + ext2_fsblk_t ret; > + > + mutex_lock(&ei->truncate_mutex); > + ret = ext2_new_blocks(inode, goal, &count, errp); > + mutex_unlock(&ei->truncate_mutex); > > - return ext2_new_blocks(inode, goal, &count, errp); > + return ret; > } > > #ifdef EXT2FS_DEBUG > -- > 2.31.1 >
On 2023/8/14 20:46, Jan Kara wrote: > On Fri 11-08-23 11:38:56, Ye Bin wrote: >> There's a issue as follows: >> Block Allocation Reservation Windows Map (ext2_try_to_allocate_with_rsv): >> reservation window 0x000000006f105382 start: 0, end: 0 >> reservation window 0x000000008fd1a555 start: 1044, end: 1059 >> Window map complete. >> kernel BUG at fs/ext2/balloc.c:1158! >> invalid opcode: 0000 [#1] PREEMPT SMP KASAN >> RIP: 0010:ext2_try_to_allocate_with_rsv.isra.0+0x15c4/0x1800 >> Call Trace: >> <TASK> >> ext2_new_blocks+0x935/0x1690 >> ext2_new_block+0x73/0xa0 >> ext2_xattr_set2+0x74f/0x1730 >> ext2_xattr_set+0x12b6/0x2260 >> ext2_xattr_user_set+0x9c/0x110 >> __vfs_setxattr+0x139/0x1d0 >> __vfs_setxattr_noperm+0xfc/0x370 >> __vfs_setxattr_locked+0x205/0x2c0 >> vfs_setxattr+0x19d/0x3b0 >> do_setxattr+0xff/0x220 >> setxattr+0x123/0x150 >> path_setxattr+0x193/0x1e0 >> __x64_sys_setxattr+0xc8/0x170 >> do_syscall_64+0x35/0x80 >> entry_SYSCALL_64_after_hwframe+0x63/0xcd >> >> Above issue may happens as follows: >> setxattr write back >> ext2_xattr_set >> ext2_xattr_set2 >> ext2_new_block >> ext2_new_blocks >> ext2_try_to_allocate_with_rsv >> alloc_new_reservation >> --> group=0 [0, 1023] rsv [1016, 1023] >> do_writepages >> mpage_writepages >> write_cache_pages >> __mpage_writepage >> ext2_get_block >> ext2_get_blocks >> ext2_alloc_branch >> ext2_new_blocks >> ext2_try_to_allocate_with_rsv >> alloc_new_reservation >> -->group=1 [1024, 2047] rsv [1044, 1059] >> if ((my_rsv->rsv_start > group_last_block) || >> (my_rsv->rsv_end < group_first_block) >> rsv_window_dump >> BUG(); >> Now ext2 mkwrite delay allocate new blocks. So there maybe allocate blocks when >> do write back. However, there is no concurrent protection between >> ext2_xattr_set() and do_writepages(). >> To solve about issue hold '&ei->truncate_mutex' lock when new block for xattr. >> >> Signed-off-by: Ye Bin <yebin10@huawei.com> > Thanks for the patch! I agree the handling of reservation window and its > use for block allocation needs to be protected by ei->i_truncate_mutex. > However in this particular case of xattr allocation where we want to > allocate just one block which is completely independent of file data, I'd > rather choose to make ext2_new_blocks() ignore the reservation window (set > my_rsv to NULL). There's already a logic at the beginning of > ext2_new_blocks() deciding whether to use the reservation window or not and > we could extend it - probably by adding flags argument to it a introducing > a NORESERVE flag. > > Also as a preparatory patch, I'd just remove ext2_new_block() and opencode > it in the xattr code since it has only that one user anyway. > > Honza > Thanks for your suggestion. I will send new version according to your suggestion. > >> --- >> fs/ext2/balloc.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c >> index c8049c90323d..039f655febfd 100644 >> --- a/fs/ext2/balloc.c >> +++ b/fs/ext2/balloc.c >> @@ -1432,8 +1432,14 @@ ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal, >> ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp) >> { >> unsigned long count = 1; >> + struct ext2_inode_info *ei = EXT2_I(inode); >> + ext2_fsblk_t ret; >> + >> + mutex_lock(&ei->truncate_mutex); >> + ret = ext2_new_blocks(inode, goal, &count, errp); >> + mutex_unlock(&ei->truncate_mutex); >> >> - return ext2_new_blocks(inode, goal, &count, errp); >> + return ret; >> } >> >> #ifdef EXT2FS_DEBUG >> -- >> 2.31.1 >>
diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c index c8049c90323d..039f655febfd 100644 --- a/fs/ext2/balloc.c +++ b/fs/ext2/balloc.c @@ -1432,8 +1432,14 @@ ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal, ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp) { unsigned long count = 1; + struct ext2_inode_info *ei = EXT2_I(inode); + ext2_fsblk_t ret; + + mutex_lock(&ei->truncate_mutex); + ret = ext2_new_blocks(inode, goal, &count, errp); + mutex_unlock(&ei->truncate_mutex); - return ext2_new_blocks(inode, goal, &count, errp); + return ret; } #ifdef EXT2FS_DEBUG
There's a issue as follows: Block Allocation Reservation Windows Map (ext2_try_to_allocate_with_rsv): reservation window 0x000000006f105382 start: 0, end: 0 reservation window 0x000000008fd1a555 start: 1044, end: 1059 Window map complete. kernel BUG at fs/ext2/balloc.c:1158! invalid opcode: 0000 [#1] PREEMPT SMP KASAN RIP: 0010:ext2_try_to_allocate_with_rsv.isra.0+0x15c4/0x1800 Call Trace: <TASK> ext2_new_blocks+0x935/0x1690 ext2_new_block+0x73/0xa0 ext2_xattr_set2+0x74f/0x1730 ext2_xattr_set+0x12b6/0x2260 ext2_xattr_user_set+0x9c/0x110 __vfs_setxattr+0x139/0x1d0 __vfs_setxattr_noperm+0xfc/0x370 __vfs_setxattr_locked+0x205/0x2c0 vfs_setxattr+0x19d/0x3b0 do_setxattr+0xff/0x220 setxattr+0x123/0x150 path_setxattr+0x193/0x1e0 __x64_sys_setxattr+0xc8/0x170 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Above issue may happens as follows: setxattr write back ext2_xattr_set ext2_xattr_set2 ext2_new_block ext2_new_blocks ext2_try_to_allocate_with_rsv alloc_new_reservation --> group=0 [0, 1023] rsv [1016, 1023] do_writepages mpage_writepages write_cache_pages __mpage_writepage ext2_get_block ext2_get_blocks ext2_alloc_branch ext2_new_blocks ext2_try_to_allocate_with_rsv alloc_new_reservation -->group=1 [1024, 2047] rsv [1044, 1059] if ((my_rsv->rsv_start > group_last_block) || (my_rsv->rsv_end < group_first_block) rsv_window_dump BUG(); Now ext2 mkwrite delay allocate new blocks. So there maybe allocate blocks when do write back. However, there is no concurrent protection between ext2_xattr_set() and do_writepages(). To solve about issue hold '&ei->truncate_mutex' lock when new block for xattr. Signed-off-by: Ye Bin <yebin10@huawei.com> --- fs/ext2/balloc.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)