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Date: Sun, 22 Jan 2017 17:25:27 -0500
From: Theodore Ts'o <tytso@....edu>
To: Jan Kara <jack@...e.cz>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>,
linux@...encehorizons.net, stable@...r.kernel.org, #@...nk.org
Subject: Re: [PATCH 2/4] ext4: fix deadlock between inline_data and
ext4_expand_extra_isize_ea()
On Fri, Jan 20, 2017 at 02:53:17PM +0100, Jan Kara wrote:
> > @@ -1264,7 +1262,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
> > ext4_xattr_update_super_block(handle, inode->i_sb);
> > inode->i_ctime = current_time(inode);
> > if (!value)
> > - ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
> > + no_expand = 0;
>
> OK. I suppose you can use ext4_mark_inode_dirty() instead of
> ext4_mark_iloc_dirty() because the deadlock on xattr_sem is now taken care
> of by your changes, right?
Correct.
> > @@ -1497,12 +1493,11 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
> > int error = 0, tried_min_extra_isize = 0;
> > int s_min_extra_isize = le16_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_min_extra_isize);
> > int isize_diff; /* How much do we need to grow i_extra_isize */
> > + int no_expand;
> > +
> > + if (ext4_write_trylock_xattr(inode, &no_expand) == 0)
> > + return 0;
>
> Why do you play tricks with trylock here? ext4_mark_inode_dirty() checks
> EXT4_STATE_NO_EXPAND and thus we should not ever get here if we already
> hold xattr_sem...
The problem is still a lock inversion in the truncate code path. The
simplest way of dealing with it to simply avoiding doing the
expand_isize operation on truncates. In the case where this is
happening on the deletion of an inode, doing the expansion is
pointless anyway.
- Ted
inline run xfstest ext4/307
[ 248.556548] EXT4-fs (dm-1): mounted filesystem with ordered data mode. Opts: acl,user_xattr,block_validity
[ 248.602530]
[ 248.604177] ======================================================
[ 248.610565] [ INFO: possible circular locking dependency detected ]
[ 248.617163] 4.10.0-rc3-ext4-00017-ge2a392e80d24-dirty #210 Not tainted
[ 248.623999] -------------------------------------------------------
[ 248.630404] fsstress/26316 is trying to acquire lock:
[ 248.635577] (&ei->i_data_sem){++++..}, at: [<ffffffff812a1b6f>] ext4_map_blocks+0xf7/0x4f5
[ 248.644066]
[ 248.644066] but task is already holding lock:
[ 248.650023] (&ei->xattr_sem){++++..}, at: [<ffffffff812e357c>] ext4_try_add_inline_entry+0x4c/0x1db
[ 248.659291]
[ 248.659291] which lock already depends on the new lock.
[ 248.659291]
[ 248.668022]
[ 248.668022] the existing dependency chain (in reverse order) is:
[ 248.675720]
[ 248.675720] -> #1 (&ei->xattr_sem){++++..}:
[ 248.681604]
[ 248.681614] [<ffffffff8111f550>] __lock_acquire+0x5e0/0x68a
[ 248.689524]
[ 248.689531] [<ffffffff81120364>] lock_acquire+0x122/0x1bd
[ 248.697263]
[ 248.697272] [<ffffffff818464d4>] down_write+0x39/0x99
[ 248.704680]
[ 248.704689] [<ffffffff812e1279>] ext4_expand_extra_isize_ea+0x50/0x42a
[ 248.713637]
[ 248.713645] [<ffffffff812a4d92>] ext4_mark_inode_dirty+0x170/0x27b
[ 248.722156]
[ 248.722166] [<ffffffff812cd6c9>] ext4_ext_truncate+0x27/0x8c
[ 248.730165]
[ 248.730173] [<ffffffff812a65f9>] ext4_truncate+0x26e/0x47d
[ 248.737989]
[ 248.737996] [<ffffffff812a91d8>] ext4_setattr+0x70b/0x85d
[ 248.745732]
[ 248.745739] [<ffffffff8121af50>] notify_change+0x236/0x37b
[ 248.753562]
[ 248.753569] [<ffffffff811fc72a>] do_truncate+0x6f/0x8e
[ 248.761066]
[ 248.761070] [<ffffffff8120c8e5>] do_last+0x58f/0x608
[ 248.768365]
[ 248.768369] [<ffffffff8120cbe3>] path_openat+0x285/0x30c
[ 248.777907]
[ 248.777911] [<ffffffff8120ccb7>] do_filp_open+0x4d/0xa3
[ 248.785541]
[ 248.785548] [<ffffffff811fd97e>] do_sys_open+0x13c/0x1cb
[ 248.793178]
[ 248.793183] [<ffffffff811fda2b>] SyS_open+0x1e/0x20
[ 248.800494]
[ 248.800502] [<ffffffff81848a01>] entry_SYSCALL_64_fastpath+0x1f/0xc2
[ 248.809230]
[ 248.809230] -> #0 (&ei->i_data_sem){++++..}:
[ 248.815091]
[ 248.815098] [<ffffffff8111ca13>] validate_chain.isra.20+0xaf7/0x1109
[ 248.823951]
[ 248.823956] [<ffffffff8111f550>] __lock_acquire+0x5e0/0x68a
[ 248.831880]
[ 248.831885] [<ffffffff81120364>] lock_acquire+0x122/0x1bd
[ 248.843958]
[ 248.843964] [<ffffffff81846444>] down_read+0x30/0x87
[ 248.851379]
[ 248.851390] [<ffffffff812a1b6f>] ext4_map_blocks+0xf7/0x4f5
[ 248.859409]
[ 248.859416] [<ffffffff812e21dc>] ext4_convert_inline_data_nolock+0xf0/0x33d
[ 248.868712]
[ 248.868720] [<ffffffff812e36b7>] ext4_try_add_inline_entry+0x187/0x1db
[ 248.877775]
[ 248.877780] [<ffffffff812af8bc>] ext4_add_entry+0xccc/0xd55
[ 248.886237]
[ 248.886240] [<ffffffff812af963>] ext4_add_nondir+0x1e/0x6b
[ 248.894163]
[ 248.894168] [<ffffffff812b1be1>] ext4_symlink+0x37b/0x41c
[ 248.902228]
[ 248.902233] [<ffffffff8120db52>] vfs_symlink+0xd9/0x134
[ 248.909877]
[ 248.909880] [<ffffffff8120dc2b>] SyS_symlinkat+0x7e/0xc3
[ 248.917592]
[ 248.917600] [<ffffffff8120dc86>] SyS_symlink+0x16/0x18
[ 248.925587]
[ 248.925599] [<ffffffff81848a01>] entry_SYSCALL_64_fastpath+0x1f/0xc2
[ 248.934482]
[ 248.934482] other info that might help us debug this:
[ 248.934482]
[ 248.942591] Possible unsafe locking scenario:
[ 248.942591]
[ 248.948629] CPU0 CPU1
[ 248.953271] ---- ----
[ 248.957906] lock(&ei->xattr_sem);
[ 248.961507] lock(&ei->i_data_sem);
[ 248.967719] lock(&ei->xattr_sem);
[ 248.973835] lock(&ei->i_data_sem);
[ 248.977578]
[ 248.977578] *** DEADLOCK ***
[ 248.977578]
[ 248.983621] 4 locks held by fsstress/26316:
[ 248.987911] #0: (sb_writers#3){.+.+.+}, at: [<ffffffff8121e549>] mnt_want_write+0x21/0x45
[ 248.996377] #1: (&type->i_mutex_dir_key/1){+.+.+.}, at: [<ffffffff8120ac5a>] filename_create+0x72/0x11c
[ 249.006145] #2: (jbd2_handle){++++..}, at: [<ffffffff812f02ec>] start_this_handle+0x33d/0x3bf
[ 249.014958] #3: (&ei->xattr_sem){++++..}, at: [<ffffffff812e357c>] ext4_try_add_inline_entry+0x4c/0x1db
[ 249.024650]
[ 249.024650] stack backtrace:
[ 249.029143] CPU: 1 PID: 26316 Comm: fsstress Not tainted 4.10.0-rc3-ext4-00017-ge2a392e80d24-dirty #210
[ 249.038654] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[ 249.048007] Call Trace:
[ 249.050573] dump_stack+0x85/0xbe
[ 249.054016] print_circular_bug+0x290/0x29e
[ 249.058315] validate_chain.isra.20+0xaf7/0x1109
[ 249.063057] __lock_acquire+0x5e0/0x68a
[ 249.067002] ? __lock_acquire+0x5e0/0x68a
[ 249.071126] lock_acquire+0x122/0x1bd
[ 249.074899] ? ext4_map_blocks+0xf7/0x4f5
[ 249.079022] down_read+0x30/0x87
[ 249.082367] ? ext4_map_blocks+0xf7/0x4f5
[ 249.086483] ext4_map_blocks+0xf7/0x4f5
[ 249.090428] ext4_convert_inline_data_nolock+0xf0/0x33d
[ 249.095763] ext4_try_add_inline_entry+0x187/0x1db
[ 249.100666] ext4_add_entry+0xccc/0xd55
[ 249.104616] ? __ext4_handle_dirty_metadata+0xca/0x1af
[ 249.109868] ? ext4_mark_iloc_dirty+0x660/0x6a9
[ 249.114509] ext4_add_nondir+0x1e/0x6b
[ 249.118366] ext4_symlink+0x37b/0x41c
[ 249.122151] ? __inode_permission+0x81/0x88
[ 249.126457] vfs_symlink+0xd9/0x134
[ 249.130056] SyS_symlinkat+0x7e/0xc3
[ 249.133751] ? trace_hardirqs_on_thunk+0x1a/0x1c
[ 249.138488] SyS_symlink+0x16/0x18
[ 249.142002] entry_SYSCALL_64_fastpath+0x1f/0xc2
[ 249.146737] RIP: 0033:0x7f02be12f237
[ 249.150425] RSP: 002b:00007ffca0afdca8 EFLAGS: 00000206 ORIG_RAX: 0000000000000058
[ 249.158119] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f02be12f237
[ 249.165492] RDX: 000000000000006c RSI: 00007f02b80008c0 RDI: 00007f02b8000d80
[ 249.173094] RBP: 0000000000000032 R08: 0000000000000003 R09: 00007f02b8000070
[ 249.180339] R10: 00007f02be3f6760 R11: 0000000000000206 R12: 0000000051eb851f
[ 249.187581] R13: 0000000000405020 R14: 0000000000000000 R15: 0000000000000000
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