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Message-ID: <20190312200932.GD45421@jaegeuk-macbookpro.roam.corp.google.com>
Date: Tue, 12 Mar 2019 13:09:32 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <yuchao0@...wei.com>
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH] f2fs: fix to avoid deadlock in f2fs_read_inline_dir()
On 03/12, Chao Yu wrote:
> As Jiqun Li reported in bugzilla:
>
> https://bugzilla.kernel.org/show_bug.cgi?id=202883
>
> sometimes, dead lock when make system call SYS_getdents64 with fsync() is
> called by another process.
>
> monkey running on android9.0
>
> 1. task 9785 held sbi->cp_rwsem and waiting lock_page()
> 2. task 10349 held mm_sem and waiting sbi->cp_rwsem
> 3. task 9709 held lock_page() and waiting mm_sem
>
> so this is a dead lock scenario.
>
> task stack is show by crash tools as following
>
> crash_arm64> bt ffffffc03c354080
> PID: 9785 TASK: ffffffc03c354080 CPU: 1 COMMAND: "RxIoScheduler-3"
> >> #7 [ffffffc01b50fac0] __lock_page at ffffff80081b11e8
>
> crash-arm64> bt 10349
> PID: 10349 TASK: ffffffc018b83080 CPU: 1 COMMAND: "BUGLY_ASYNC_UPL"
> >> #3 [ffffffc01f8cfa40] rwsem_down_read_failed at ffffff8008a93afc
> PC: 00000033 LR: 00000000 SP: 00000000 PSTATE: ffffffffffffffff
>
> crash-arm64> bt 9709
> PID: 9709 TASK: ffffffc03e7f3080 CPU: 1 COMMAND: "IntentService[A"
> >> #3 [ffffffc001e67850] rwsem_down_read_failed at ffffff8008a93afc
> >> #8 [ffffffc001e67b80] el1_ia at ffffff8008084fc4
> PC: ffffff8008274114 [compat_filldir64+120]
> LR: ffffff80083584d4 [f2fs_fill_dentries+448]
> SP: ffffffc001e67b80 PSTATE: 80400145
> X29: ffffffc001e67b80 X28: 0000000000000000 X27: 000000000000001a
> X26: 00000000000093d7 X25: ffffffc070d52480 X24: 0000000000000008
> X23: 0000000000000028 X22: 00000000d43dfd60 X21: ffffffc001e67e90
> X20: 0000000000000011 X19: ffffff80093a4000 X18: 0000000000000000
> X17: 0000000000000000 X16: 0000000000000000 X15: 0000000000000000
> X14: ffffffffffffffff X13: 0000000000000008 X12: 0101010101010101
> X11: 7f7f7f7f7f7f7f7f X10: 6a6a6a6a6a6a6a6a X9: 7f7f7f7f7f7f7f7f
> X8: 0000000080808000 X7: ffffff800827409c X6: 0000000080808000
> X5: 0000000000000008 X4: 00000000000093d7 X3: 000000000000001a
> X2: 0000000000000011 X1: ffffffc070d52480 X0: 0000000000800238
> >> #9 [ffffffc001e67be0] f2fs_fill_dentries at ffffff80083584d0
> PC: 0000003c LR: 00000000 SP: 00000000 PSTATE: 000000d9
> X12: f48a02ff X11: d4678960 X10: d43dfc00 X9: d4678ae4
> X8: 00000058 X7: d4678994 X6: d43de800 X5: 000000d9
> X4: d43dfc0c X3: d43dfc10 X2: d46799c8 X1: 00000000
> X0: 00001068
>
> Below potential deadlock will happen between three threads:
> Thread A Thread B Thread C
> - f2fs_do_sync_file
> - f2fs_write_checkpoint
> - down_write(&sbi->node_change) -- 1)
> - do_page_fault
> - down_write(&mm->mmap_sem) -- 2)
> - do_wp_page
> - f2fs_vm_page_mkwrite
> - getdents64
> - f2fs_read_inline_dir
> - lock_page -- 3)
> - f2fs_sync_node_pages
> - lock_page -- 3)
> - __do_map_lock
> - down_read(&sbi->node_change) -- 1)
> - f2fs_fill_dentries
> - dir_emit
> - compat_filldir64
> - do_page_fault
> - down_read(&mm->mmap_sem) -- 2)
>
> Since f2fs_readdir is protected by inode.i_rwsem, there should not be
Well, what about other dir operations which can convert inline_dentry?
How about allocating a buffer shortly like this?
---
fs/f2fs/inline.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index a1381d05956b..50a946d55778 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -647,12 +647,10 @@ int f2fs_read_inline_dir(struct file *file, struct dir_context *ctx,
struct inode *inode = file_inode(file);
struct page *ipage = NULL;
struct f2fs_dentry_ptr d;
- void *inline_dentry = NULL;
+ void *inline_dentry = NULL, *buf = NULL;
int err;
- make_dentry_ptr_inline(inode, &d, inline_dentry);
-
- if (ctx->pos == d.max)
+ if (ctx->pos >= NR_INLINE_DENTRY(inode))
return 0;
ipage = f2fs_get_node_page(F2FS_I_SB(inode), inode->i_ino);
@@ -660,14 +658,24 @@ int f2fs_read_inline_dir(struct file *file, struct dir_context *ctx,
return PTR_ERR(ipage);
inline_dentry = inline_data_addr(inode, ipage);
+ buf = f2fs_kmalloc(F2FS_I_SB(inode),
+ MAX_INLINE_DATA(inode), GFP_F2FS_ZERO);
+ if (!buf) {
+ f2fs_put_page(ipage, 1);
+ err = -ENOMEM;
+ goto out;
+ }
+ memcpy(buf, inline_dentry, MAX_INLINE_DATA(inode));
+ make_dentry_ptr_inline(inode, &d, buf);
- make_dentry_ptr_inline(inode, &d, inline_dentry);
+ f2fs_put_page(ipage, 1);
err = f2fs_fill_dentries(ctx, &d, 0, fstr);
if (!err)
ctx->pos = d.max;
- f2fs_put_page(ipage, 1);
+ kvfree(buf);
+out:
return err < 0 ? err : 0;
}
--
2.19.0.605.g01d371f741-goog
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