[PATCH 3.18.y 1/5] ext4: fix deadlock between inline_data and ext4_expand_extra_isize_ea()

From: Theodore Ts'o tytso@mit.edu

commit c755e251357a0cee0679081f08c3f4ba797a8009 upstream.

The xattr_sem deadlock problems fixed in commit 2e81a4eeedca: "ext4: avoid deadlock when expanding inode size" didn't include the use of xattr_sem in fs/ext4/inline.c. With the addition of project quota which added a new extra inode field, this exposed deadlocks in the inline_data code similar to the ones fixed by 2e81a4eeedca.

The deadlock can be reproduced via:

dmesg -n 7 mke2fs -t ext4 -O inline_data -Fq -I 256 /dev/vdc 32768 mount -t ext4 -o debug_want_extra_isize=24 /dev/vdc /vdc mkdir /vdc/a umount /vdc mount -t ext4 /dev/vdc /vdc echo foo > /vdc/a/foo

and looks like this:

[ 11.158815] [ 11.160276] ============================================= [ 11.161960] [ INFO: possible recursive locking detected ] [ 11.161960] 4.10.0-rc3-00015-g011b30a8a3cf #160 Tainted: G W [ 11.161960] --------------------------------------------- [ 11.161960] bash/2519 is trying to acquire lock: [ 11.161960] (&ei->xattr_sem){++++..}, at: [<c1225a4b>] ext4_expand_extra_isize_ea+0x3d/0x4cd [ 11.161960] [ 11.161960] but task is already holding lock: [ 11.161960] (&ei->xattr_sem){++++..}, at: [<c1227941>] ext4_try_add_inline_entry+0x3a/0x152 [ 11.161960] [ 11.161960] other info that might help us debug this: [ 11.161960] Possible unsafe locking scenario: [ 11.161960] [ 11.161960] CPU0 [ 11.161960] ---- [ 11.161960] lock(&ei->xattr_sem); [ 11.161960] lock(&ei->xattr_sem); [ 11.161960] [ 11.161960] *** DEADLOCK *** [ 11.161960] [ 11.161960] May be due to missing lock nesting notation [ 11.161960] [ 11.161960] 4 locks held by bash/2519: [ 11.161960] #0: (sb_writers#3){.+.+.+}, at: [<c11a2414>] mnt_want_write+0x1e/0x3e [ 11.161960] #1: (&type->i_mutex_dir_key){++++++}, at: [<c119508b>] path_openat+0x338/0x67a [ 11.161960] #2: (jbd2_handle){++++..}, at: [<c123314a>] start_this_handle+0x582/0x622 [ 11.161960] #3: (&ei->xattr_sem){++++..}, at: [<c1227941>] ext4_try_add_inline_entry+0x3a/0x152 [ 11.161960] [ 11.161960] stack backtrace: [ 11.161960] CPU: 0 PID: 2519 Comm: bash Tainted: G W 4.10.0-rc3-00015-g011b30a8a3cf #160 [ 11.161960] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-1 04/01/2014 [ 11.161960] Call Trace: [ 11.161960] dump_stack+0x72/0xa3 [ 11.161960] __lock_acquire+0xb7c/0xcb9 [ 11.161960] ? kvm_clock_read+0x1f/0x29 [ 11.161960] ? __lock_is_held+0x36/0x66 [ 11.161960] ? __lock_is_held+0x36/0x66 [ 11.161960] lock_acquire+0x106/0x18a [ 11.161960] ? ext4_expand_extra_isize_ea+0x3d/0x4cd [ 11.161960] down_write+0x39/0x72 [ 11.161960] ? ext4_expand_extra_isize_ea+0x3d/0x4cd [ 11.161960] ext4_expand_extra_isize_ea+0x3d/0x4cd [ 11.161960] ? _raw_read_unlock+0x22/0x2c [ 11.161960] ? jbd2_journal_extend+0x1e2/0x262 [ 11.161960] ? __ext4_journal_get_write_access+0x3d/0x60 [ 11.161960] ext4_mark_inode_dirty+0x17d/0x26d [ 11.161960] ? ext4_add_dirent_to_inline.isra.12+0xa5/0xb2 [ 11.161960] ext4_add_dirent_to_inline.isra.12+0xa5/0xb2 [ 11.161960] ext4_try_add_inline_entry+0x69/0x152 [ 11.161960] ext4_add_entry+0xa3/0x848 [ 11.161960] ? __brelse+0x14/0x2f [ 11.161960] ? _raw_spin_unlock_irqrestore+0x44/0x4f [ 11.161960] ext4_add_nondir+0x17/0x5b [ 11.161960] ext4_create+0xcf/0x133 [ 11.161960] ? ext4_mknod+0x12f/0x12f [ 11.161960] lookup_open+0x39e/0x3fb [ 11.161960] ? __wake_up+0x1a/0x40 [ 11.161960] ? lock_acquire+0x11e/0x18a [ 11.161960] path_openat+0x35c/0x67a [ 11.161960] ? sched_clock_cpu+0xd7/0xf2 [ 11.161960] do_filp_open+0x36/0x7c [ 11.161960] ? _raw_spin_unlock+0x22/0x2c [ 11.161960] ? __alloc_fd+0x169/0x173 [ 11.161960] do_sys_open+0x59/0xcc [ 11.161960] SyS_open+0x1d/0x1f [ 11.161960] do_int80_syscall_32+0x4f/0x61 [ 11.161960] entry_INT80_32+0x2f/0x2f [ 11.161960] EIP: 0xb76ad469 [ 11.161960] EFLAGS: 00000286 CPU: 0 [ 11.161960] EAX: ffffffda EBX: 08168ac8 ECX: 00008241 EDX: 000001b6 [ 11.161960] ESI: b75e46bc EDI: b7755000 EBP: bfbdb108 ESP: bfbdafc0 [ 11.161960] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b

Cc: stable@vger.kernel.org # 3.10 (requires 2e81a4eeedca as a prereq) Reported-by: George Spelvin linux@sciencehorizons.net Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Harsh Shandilya harsh@prjkt.io --- fs/ext4/inline.c | 66 ++++++++++++++++++++++-------------------------- fs/ext4/xattr.c | 30 +++++++++------------- fs/ext4/xattr.h | 32 +++++++++++++++++++++++ 3 files changed, 74 insertions(+), 54 deletions(-)

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 8fc2357c6867..5070616e6247 100644 --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -374,7 +374,7 @@ out: static int ext4_prepare_inline_data(handle_t *handle, struct inode *inode, unsigned int len) { - int ret, size; + int ret, size, no_expand; struct ext4_inode_info *ei = EXT4_I(inode);

if (!ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) @@ -384,15 +384,14 @@ static int ext4_prepare_inline_data(handle_t *handle, struct inode *inode, if (size < len) return -ENOSPC;

- down_write(&EXT4_I(inode)->xattr_sem); + ext4_write_lock_xattr(inode, &no_expand);

if (ei->i_inline_off) ret = ext4_update_inline_data(handle, inode, len); else ret = ext4_create_inline_data(handle, inode, len);

- up_write(&EXT4_I(inode)->xattr_sem); - + ext4_write_unlock_xattr(inode, &no_expand); return ret; }

@@ -522,7 +521,7 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping, struct inode *inode, unsigned flags) { - int ret, needed_blocks; + int ret, needed_blocks, no_expand; handle_t *handle = NULL; int retries = 0, sem_held = 0; struct page *page = NULL; @@ -562,7 +561,7 @@ retry: goto out; }

- down_write(&EXT4_I(inode)->xattr_sem); + ext4_write_lock_xattr(inode, &no_expand); sem_held = 1; /* If some one has already done this for us, just exit. */ if (!ext4_has_inline_data(inode)) { @@ -598,7 +597,7 @@ retry: page_cache_release(page); page = NULL; ext4_orphan_add(handle, inode); - up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand); sem_held = 0; ext4_journal_stop(handle); handle = NULL; @@ -624,7 +623,7 @@ out: page_cache_release(page); } if (sem_held) - up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand); if (handle) ext4_journal_stop(handle); brelse(iloc.bh); @@ -717,7 +716,7 @@ convert: int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len, unsigned copied, struct page *page) { - int ret; + int ret, no_expand; void *kaddr; struct ext4_iloc iloc;

@@ -735,7 +734,7 @@ int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len, goto out; }

- down_write(&EXT4_I(inode)->xattr_sem); + ext4_write_lock_xattr(inode, &no_expand); BUG_ON(!ext4_has_inline_data(inode));

kaddr = kmap_atomic(page); @@ -745,7 +744,7 @@ int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len, /* clear page dirty so that writepages wouldn't work for us. */ ClearPageDirty(page);

- up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand); brelse(iloc.bh); out: return copied; @@ -756,7 +755,7 @@ ext4_journalled_write_inline_data(struct inode *inode, unsigned len, struct page *page) { - int ret; + int ret, no_expand; void *kaddr; struct ext4_iloc iloc;

@@ -766,11 +765,11 @@ ext4_journalled_write_inline_data(struct inode *inode, return NULL; }

- down_write(&EXT4_I(inode)->xattr_sem); + ext4_write_lock_xattr(inode, &no_expand); kaddr = kmap_atomic(page); ext4_write_inline_data(inode, &iloc, kaddr, 0, len); kunmap_atomic(kaddr); - up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand);

return iloc.bh; } @@ -1245,7 +1244,7 @@ out: int ext4_try_add_inline_entry(handle_t *handle, struct dentry *dentry, struct inode *inode) { - int ret, inline_size; + int ret, inline_size, no_expand; void *inline_start; struct ext4_iloc iloc; struct inode *dir = dentry->d_parent->d_inode; @@ -1254,7 +1253,7 @@ int ext4_try_add_inline_entry(handle_t *handle, struct dentry *dentry, if (ret) return ret;

- down_write(&EXT4_I(dir)->xattr_sem); + ext4_write_lock_xattr(dir, &no_expand); if (!ext4_has_inline_data(dir)) goto out;

@@ -1299,7 +1298,7 @@ int ext4_try_add_inline_entry(handle_t *handle, struct dentry *dentry,

out: ext4_mark_inode_dirty(handle, dir); - up_write(&EXT4_I(dir)->xattr_sem); + ext4_write_unlock_xattr(dir, &no_expand); brelse(iloc.bh); return ret; } @@ -1655,7 +1654,7 @@ int ext4_delete_inline_entry(handle_t *handle, struct buffer_head *bh, int *has_inline_data) { - int err, inline_size; + int err, inline_size, no_expand; struct ext4_iloc iloc; void *inline_start;

@@ -1663,7 +1662,7 @@ int ext4_delete_inline_entry(handle_t *handle, if (err) return err;

- down_write(&EXT4_I(dir)->xattr_sem); + ext4_write_lock_xattr(dir, &no_expand); if (!ext4_has_inline_data(dir)) { *has_inline_data = 0; goto out; @@ -1698,7 +1697,7 @@ int ext4_delete_inline_entry(handle_t *handle,

ext4_show_inline_dir(dir, iloc.bh, inline_start, inline_size); out: - up_write(&EXT4_I(dir)->xattr_sem); + ext4_write_unlock_xattr(dir, &no_expand); brelse(iloc.bh); if (err != -ENOENT) ext4_std_error(dir->i_sb, err); @@ -1797,11 +1796,11 @@ out:

int ext4_destroy_inline_data(handle_t *handle, struct inode *inode) { - int ret; + int ret, no_expand;

- down_write(&EXT4_I(inode)->xattr_sem); + ext4_write_lock_xattr(inode, &no_expand); ret = ext4_destroy_inline_data_nolock(handle, inode); - up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand);

return ret; } @@ -1879,7 +1878,7 @@ out: void ext4_inline_data_truncate(struct inode *inode, int *has_inline) { handle_t *handle; - int inline_size, value_len, needed_blocks; + int inline_size, value_len, needed_blocks, no_expand; size_t i_size; void *value = NULL; struct ext4_xattr_ibody_find is = { @@ -1896,7 +1895,7 @@ void ext4_inline_data_truncate(struct inode *inode, int *has_inline) if (IS_ERR(handle)) return;

- down_write(&EXT4_I(inode)->xattr_sem); + ext4_write_lock_xattr(inode, &no_expand); if (!ext4_has_inline_data(inode)) { *has_inline = 0; ext4_journal_stop(handle); @@ -1954,7 +1953,7 @@ out_error: up_write(&EXT4_I(inode)->i_data_sem); out: brelse(is.iloc.bh); - up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand); kfree(value); if (inode->i_nlink) ext4_orphan_del(handle, inode); @@ -1970,7 +1969,7 @@ out:

int ext4_convert_inline_data(struct inode *inode) { - int error, needed_blocks; + int error, needed_blocks, no_expand; handle_t *handle; struct ext4_iloc iloc;

@@ -1992,15 +1991,10 @@ int ext4_convert_inline_data(struct inode *inode) goto out_free; }

- down_write(&EXT4_I(inode)->xattr_sem); - if (!ext4_has_inline_data(inode)) { - up_write(&EXT4_I(inode)->xattr_sem); - goto out; - } - - error = ext4_convert_inline_data_nolock(handle, inode, &iloc); - up_write(&EXT4_I(inode)->xattr_sem); -out: + ext4_write_lock_xattr(inode, &no_expand); + if (ext4_has_inline_data(inode)) + error = ext4_convert_inline_data_nolock(handle, inode, &iloc); + ext4_write_unlock_xattr(inode, &no_expand); ext4_journal_stop(handle); out_free: brelse(iloc.bh); diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index c57c83806fb9..c8d782bf8c5c 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -1120,16 +1120,14 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index, struct ext4_xattr_block_find bs = { .s = { .not_found = -ENODATA, }, }; - unsigned long no_expand; + int no_expand; int error;

if (!name) return -EINVAL; if (strlen(name) > 255) return -ERANGE; - down_write(&EXT4_I(inode)->xattr_sem); - no_expand = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND); - ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND); + ext4_write_lock_xattr(inode, &no_expand);

error = ext4_reserve_inode_write(handle, inode, &is.iloc); if (error) @@ -1190,7 +1188,7 @@ 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 = ext4_current_time(inode); if (!value) - ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND); + no_expand = 0; error = ext4_mark_iloc_dirty(handle, inode, &is.iloc); /* * The bh is consumed by ext4_mark_iloc_dirty, even with @@ -1204,9 +1202,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index, cleanup: brelse(is.iloc.bh); brelse(bs.bh); - if (no_expand == 0) - ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND); - up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand); return error; }

@@ -1289,12 +1285,11 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize, void *base, *start, *end; int extra_isize = 0, 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 no_expand; + + if (ext4_write_trylock_xattr(inode, &no_expand) == 0) + return 0;

- down_write(&EXT4_I(inode)->xattr_sem); - /* - * Set EXT4_STATE_NO_EXPAND to avoid recursion when marking inode dirty - */ - ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND); retry: if (EXT4_I(inode)->i_extra_isize >= new_extra_isize) goto out; @@ -1487,8 +1482,7 @@ retry: } brelse(bh); out: - ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND); - up_write(&EXT4_I(inode)->xattr_sem); + ext4_write_unlock_xattr(inode, &no_expand); return 0;

cleanup: @@ -1500,10 +1494,10 @@ cleanup: kfree(bs); brelse(bh); /* - * We deliberately leave EXT4_STATE_NO_EXPAND set here since inode - * size expansion failed. + * Inode size expansion failed; don't try again */ - up_write(&EXT4_I(inode)->xattr_sem); + no_expand = 1; + ext4_write_unlock_xattr(inode, &no_expand); return error; }

diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h index 29bedf5589f6..2e8f23e78bc2 100644 --- a/fs/ext4/xattr.h +++ b/fs/ext4/xattr.h @@ -98,6 +98,38 @@ extern const struct xattr_handler ext4_xattr_user_handler; extern const struct xattr_handler ext4_xattr_trusted_handler; extern const struct xattr_handler ext4_xattr_security_handler;

+/* + * The EXT4_STATE_NO_EXPAND is overloaded and used for two purposes. + * The first is to signal that there the inline xattrs and data are + * taking up so much space that we might as well not keep trying to + * expand it. The second is that xattr_sem is taken for writing, so + * we shouldn't try to recurse into the inode expansion. For this + * second case, we need to make sure that we take save and restore the + * NO_EXPAND state flag appropriately. + */ +static inline void ext4_write_lock_xattr(struct inode *inode, int *save) +{ + down_write(&EXT4_I(inode)->xattr_sem); + *save = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND); + ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND); +} + +static inline int ext4_write_trylock_xattr(struct inode *inode, int *save) +{ + if (down_write_trylock(&EXT4_I(inode)->xattr_sem) == 0) + return 0; + *save = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND); + ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND); + return 1; +} + +static inline void ext4_write_unlock_xattr(struct inode *inode, int *save) +{ + if (*save == 0) + ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND); + up_write(&EXT4_I(inode)->xattr_sem); +} + extern ssize_t ext4_listxattr(struct dentry *, char *, size_t);

extern int ext4_xattr_get(struct inode *, int, const char *, void *, size_t);