[PATCH AUTOSEL 4.19 059/206] ext4: make dioread_nolock the default

[PATCH AUTOSEL 4.19 059/206] ext4: make dioread_nolock the default

[Sasha Levin]

From: Theodore Ts'o <tytso@mit.edu>

[ Upstream commit 244adf6426ee31a83f397b700d964cff12a247d3 ]

This fixes the direct I/O versus writeback race which can reveal stale
data, and it improves the tail latency of commits on slow devices.

Link: https://lore.kernel.org/r/20200125022254.1101588-1-tytso@mit.edu
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/super.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 0c15ff19acbd4..0076ea7427e34 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1538,6 +1538,7 @@ static const match_table_t tokens = {
 	{Opt_auto_da_alloc, "auto_da_alloc"},
 	{Opt_noauto_da_alloc, "noauto_da_alloc"},
 	{Opt_dioread_nolock, "dioread_nolock"},
+	{Opt_dioread_lock, "nodioread_nolock"},
 	{Opt_dioread_lock, "dioread_lock"},
 	{Opt_discard, "discard"},
 	{Opt_nodiscard, "nodiscard"},
@@ -3712,6 +3713,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		set_opt(sb, NO_UID32);
 	/* xattr user namespace & acls are now defaulted on */
 	set_opt(sb, XATTR_USER);
+	set_opt(sb, DIOREAD_NOLOCK);
 #ifdef CONFIG_EXT4_FS_POSIX_ACL
 	set_opt(sb, POSIX_ACL);
 #endif
@@ -3849,9 +3851,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount;
 
 	if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
-		printk_once(KERN_WARNING "EXT4-fs: Warning: mounting "
-			    "with data=journal disables delayed "
-			    "allocation and O_DIRECT support!\n");
+		printk_once(KERN_WARNING "EXT4-fs: Warning: mounting with data=journal disables delayed allocation, dioread_nolock, and O_DIRECT support!\n");
+		clear_opt(sb, DIOREAD_NOLOCK);
 		if (test_opt2(sb, EXPLICIT_DELALLOC)) {
 			ext4_msg(sb, KERN_ERR, "can't mount with "
 				 "both data=journal and delalloc");
-- 
2.25.1

[PATCH AUTOSEL 4.19 097/206] ext4: fix a data race at inode->i_disksize

[Sasha Levin]

From: Qiujun Huang <hqjagain@gmail.com>

[ Upstream commit dce8e237100f60c28cc66effb526ba65a01d8cb3 ]

KCSAN find inode->i_disksize could be accessed concurrently.

BUG: KCSAN: data-race in ext4_mark_iloc_dirty / ext4_write_end

write (marked) to 0xffff8b8932f40090 of 8 bytes by task 66792 on cpu 0:
 ext4_write_end+0x53f/0x5b0
 ext4_da_write_end+0x237/0x510
 generic_perform_write+0x1c4/0x2a0
 ext4_buffered_write_iter+0x13a/0x210
 ext4_file_write_iter+0xe2/0x9b0
 new_sync_write+0x29c/0x3a0
 __vfs_write+0x92/0xa0
 vfs_write+0xfc/0x2a0
 ksys_write+0xe8/0x140
 __x64_sys_write+0x4c/0x60
 do_syscall_64+0x8a/0x2a0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8b8932f40090 of 8 bytes by task 14414 on cpu 1:
 ext4_mark_iloc_dirty+0x716/0x1190
 ext4_mark_inode_dirty+0xc9/0x360
 ext4_convert_unwritten_extents+0x1bc/0x2a0
 ext4_convert_unwritten_io_end_vec+0xc5/0x150
 ext4_put_io_end+0x82/0x130
 ext4_writepages+0xae7/0x16f0
 do_writepages+0x64/0x120
 __writeback_single_inode+0x7d/0x650
 writeback_sb_inodes+0x3a4/0x860
 __writeback_inodes_wb+0xc4/0x150
 wb_writeback+0x43f/0x510
 wb_workfn+0x3b2/0x8a0
 process_one_work+0x39b/0x7e0
 worker_thread+0x88/0x650
 kthread+0x1d4/0x1f0
 ret_from_fork+0x35/0x40

The plain read is outside of inode->i_data_sem critical section
which results in a data race. Fix it by adding READ_ONCE().

Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
Link: https://lore.kernel.org/r/1582556566-3909-1-git-send-email-hqjagain@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index cd833f4e64ef1..52be4c9650241 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5315,7 +5315,7 @@ static int ext4_do_update_inode(handle_t *handle,
 		raw_inode->i_file_acl_high =
 			cpu_to_le16(ei->i_file_acl >> 32);
 	raw_inode->i_file_acl_lo = cpu_to_le32(ei->i_file_acl);
-	if (ei->i_disksize != ext4_isize(inode->i_sb, raw_inode)) {
+	if (READ_ONCE(ei->i_disksize) != ext4_isize(inode->i_sb, raw_inode)) {
 		ext4_isize_set(raw_inode, ei->i_disksize);
 		need_datasync = 1;
 	}
-- 
2.25.1

[PATCH AUTOSEL 4.19 108/206] ext4: mark block bitmap corrupted when found instead of BUGON

[Sasha Levin]

From: Dmitry Monakhov <dmonakhov@gmail.com>

[ Upstream commit eb5760863fc28feab28b567ddcda7e667e638da0 ]

We already has similar code in ext4_mb_complex_scan_group(), but
ext4_mb_simple_scan_group() still affected.

Other reports: https://www.spinics.net/lists/linux-ext4/msg60231.html

Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Dmitry Monakhov <dmonakhov@gmail.com>
Link: https://lore.kernel.org/r/20200310150156.641-1-dmonakhov@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/mballoc.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 8dd54a8a03610..054cfdd007d69 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1901,8 +1901,15 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,
 		BUG_ON(buddy == NULL);
 
 		k = mb_find_next_zero_bit(buddy, max, 0);
-		BUG_ON(k >= max);
-
+		if (k >= max) {
+			ext4_grp_locked_error(ac->ac_sb, e4b->bd_group, 0, 0,
+				"%d free clusters of order %d. But found 0",
+				grp->bb_counters[i], i);
+			ext4_mark_group_bitmap_corrupted(ac->ac_sb,
+					 e4b->bd_group,
+					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
+			break;
+		}
 		ac->ac_found++;
 
 		ac->ac_b_ex.fe_len = 1 << i;
-- 
2.25.1

Re: [PATCH AUTOSEL 4.19 059/206] ext4: make dioread_nolock the default

[Eric Biggers]

On Thu, Sep 17, 2020 at 10:05:35PM -0400, Sasha Levin wrote:
> From: Theodore Ts'o <tytso@mit.edu>
> 
> [ Upstream commit 244adf6426ee31a83f397b700d964cff12a247d3 ]
> 
> This fixes the direct I/O versus writeback race which can reveal stale
> data, and it improves the tail latency of commits on slow devices.
> 
> Link: https://lore.kernel.org/r/20200125022254.1101588-1-tytso@mit.edu
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Any particular reason to be backporting this?  I thought I saw some fixes for
dioread_nolock go by, after it was made the default.  Are you getting all of
those fixes too?

- Eric

Re: [PATCH AUTOSEL 4.19 059/206] ext4: make dioread_nolock the default

[Theodore Y. Ts'o]

On Thu, Sep 17, 2020 at 07:58:59PM -0700, Eric Biggers wrote:
> On Thu, Sep 17, 2020 at 10:05:35PM -0400, Sasha Levin wrote:
> > From: Theodore Ts'o <tytso@mit.edu>
> > 
> > [ Upstream commit 244adf6426ee31a83f397b700d964cff12a247d3 ]
> > 
> > This fixes the direct I/O versus writeback race which can reveal stale
> > data, and it improves the tail latency of commits on slow devices.
> > 
> > Link: https://lore.kernel.org/r/20200125022254.1101588-1-tytso@mit.edu
> > Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> > Signed-off-by: Sasha Levin <sashal@kernel.org>I
> 
> Any particular reason to be backporting this?  I thought I saw some fixes for
> dioread_nolock go by, after it was made the default.  Are you getting all of
> those fixes too?

Agreed, making dioread_nolock the default has enough issues that it's
not something that I'd suggest backporting at this point.  It's a
fundamental behavioral change that it's not something we should change
in a stable kernel.

						- Ted