[PATCH AUTOSEL 4.14 16/58] ext4: update direct I/O read lock pattern for IOCB_NOWAIT

[PATCH AUTOSEL 4.14 16/58] ext4: update direct I/O read lock pattern for IOCB_NOWAIT

[Sasha Levin]

From: Matthew Bobrowski <mbobrowski@mbobrowski.org>

[ Upstream commit 548feebec7e93e58b647dba70b3303dcb569c914 ]

This patch updates the lock pattern in ext4_direct_IO_read() to not
block on inode lock in cases of IOCB_NOWAIT direct I/O reads. The
locking condition implemented here is similar to that of 942491c9e6d6
("xfs: fix AIM7 regression").

Fixes: 16c54688592c ("ext4: Allow parallel DIO reads")
Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/c5d5e759f91747359fbd2c6f9a36240cf75ad79f.1572949325.git.mbobrowski@mbobrowski.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/inode.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b3d5fd84b4856..f746abfd96977 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3787,7 +3787,13 @@ static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter)
 	 * writes & truncates and since we take care of writing back page cache,
 	 * we are protected against page writeback as well.
 	 */
-	inode_lock_shared(inode);
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!inode_trylock_shared(inode))
+			return -EAGAIN;
+	} else {
+		inode_lock_shared(inode);
+	}
+
 	ret = filemap_write_and_wait_range(mapping, iocb->ki_pos,
 					   iocb->ki_pos + count - 1);
 	if (ret)
-- 
2.20.1

[PATCH AUTOSEL 4.14 17/58] jbd2: Fix statistics for the number of logged blocks

[Sasha Levin]

From: Jan Kara <jack@suse.cz>

[ Upstream commit 015c6033068208d6227612c878877919f3fcf6b6 ]

jbd2 statistics counting number of blocks logged in a transaction was
wrong. It didn't count the commit block and more importantly it didn't
count revoke descriptor blocks. Make sure these get properly counted.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-13-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/jbd2/commit.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 0567b17a970c2..7dd6133925921 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -726,7 +726,6 @@ start_journal_io:
 				submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
 			}
 			cond_resched();
-			stats.run.rs_blocks_logged += bufs;
 
 			/* Force a new descriptor to be generated next
                            time round the loop. */
@@ -813,6 +812,7 @@ start_journal_io:
 		if (unlikely(!buffer_uptodate(bh)))
 			err = -EIO;
 		jbd2_unfile_log_bh(bh);
+		stats.run.rs_blocks_logged++;
 
 		/*
 		 * The list contains temporary buffer heads created by
@@ -858,6 +858,7 @@ start_journal_io:
 		BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 		clear_buffer_jwrite(bh);
 		jbd2_unfile_log_bh(bh);
+		stats.run.rs_blocks_logged++;
 		__brelse(bh);		/* One for getblk */
 		/* AKPM: bforget here */
 	}
@@ -879,6 +880,7 @@ start_journal_io:
 	}
 	if (cbh)
 		err = journal_wait_on_commit_record(journal, cbh);
+	stats.run.rs_blocks_logged++;
 	if (jbd2_has_feature_async_commit(journal) &&
 	    journal->j_flags & JBD2_BARRIER) {
 		blkdev_issue_flush(journal->j_dev, GFP_NOFS, NULL);
-- 
2.20.1

[PATCH AUTOSEL 4.14 33/58] ext4: fix a bug in ext4_wait_for_tail_page_commit

[Sasha Levin]

From: yangerkun <yangerkun@huawei.com>

[ Upstream commit 565333a1554d704789e74205989305c811fd9c7a ]

No need to wait for any commit once the page is fully truncated.
Besides, it may confuse e.g. concurrent ext4_writepage() with the page
still be dirty (will be cleared by truncate_pagecache() in
ext4_setattr()) but buffers has been freed; and then trigger a bug
show as below:

[   26.057508] ------------[ cut here ]------------
[   26.058531] kernel BUG at fs/ext4/inode.c:2134!
...
[   26.088130] Call trace:
[   26.088695]  ext4_writepage+0x914/0xb28
[   26.089541]  writeout.isra.4+0x1b4/0x2b8
[   26.090409]  move_to_new_page+0x3b0/0x568
[   26.091338]  __unmap_and_move+0x648/0x988
[   26.092241]  unmap_and_move+0x48c/0xbb8
[   26.093096]  migrate_pages+0x220/0xb28
[   26.093945]  kernel_mbind+0x828/0xa18
[   26.094791]  __arm64_sys_mbind+0xc8/0x138
[   26.095716]  el0_svc_common+0x190/0x490
[   26.096571]  el0_svc_handler+0x60/0xd0
[   26.097423]  el0_svc+0x8/0xc

Run the procedure (generate by syzkaller) parallel with ext3.

void main()
{
	int fd, fd1, ret;
	void *addr;
	size_t length = 4096;
	int flags;
	off_t offset = 0;
	char *str = "12345";

	fd = open("a", O_RDWR | O_CREAT);
	assert(fd >= 0);

	/* Truncate to 4k */
	ret = ftruncate(fd, length);
	assert(ret == 0);

	/* Journal data mode */
	flags = 0xc00f;
	ret = ioctl(fd, _IOW('f', 2, long), &flags);
	assert(ret == 0);

	/* Truncate to 0 */
	fd1 = open("a", O_TRUNC | O_NOATIME);
	assert(fd1 >= 0);

	addr = mmap(NULL, length, PROT_WRITE | PROT_READ,
					MAP_SHARED, fd, offset);
	assert(addr != (void *)-1);

	memcpy(addr, str, 5);
	mbind(addr, length, 0, 0, 0, MPOL_MF_MOVE);
}

And the bug will be triggered once we seen the below order.

reproduce1                         reproduce2

...                            |   ...
truncate to 4k                 |
change to journal data mode    |
                               |   memcpy(set page dirty)
truncate to 0:                 |
ext4_setattr:                  |
...                            |
ext4_wait_for_tail_page_commit |
                               |   mbind(trigger bug)
truncate_pagecache(clean dirty)|   ...
...                            |

mbind will call ext4_writepage() since the page still be dirty, and then
report the bug since the buffers has been free. Fix it by return
directly once offset equals to 0 which means the page has been fully
truncated.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: yangerkun <yangerkun@huawei.com>
Link: https://lore.kernel.org/r/20190919063508.1045-1-yangerkun@huawei.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/inode.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f746abfd96977..19c160e7f7763 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5302,11 +5302,15 @@ static void ext4_wait_for_tail_page_commit(struct inode *inode)
 
 	offset = inode->i_size & (PAGE_SIZE - 1);
 	/*
-	 * All buffers in the last page remain valid? Then there's nothing to
-	 * do. We do the check mainly to optimize the common PAGE_SIZE ==
-	 * blocksize case
+	 * If the page is fully truncated, we don't need to wait for any commit
+	 * (and we even should not as __ext4_journalled_invalidatepage() may
+	 * strip all buffers from the page but keep the page dirty which can then
+	 * confuse e.g. concurrent ext4_writepage() seeing dirty page without
+	 * buffers). Also we don't need to wait for any commit if all buffers in
+	 * the page remain valid. This is most beneficial for the common case of
+	 * blocksize == PAGESIZE.
 	 */
-	if (offset > PAGE_SIZE - i_blocksize(inode))
+	if (!offset || offset > (PAGE_SIZE - i_blocksize(inode)))
 		return;
 	while (1) {
 		page = find_lock_page(inode->i_mapping,
-- 
2.20.1

[PATCH AUTOSEL 4.14 38/58] ext4: work around deleting a file with i_nlink == 0 safely

[Sasha Levin]

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

[ Upstream commit c7df4a1ecb8579838ec8c56b2bb6a6716e974f37 ]

If the file system is corrupted such that a file's i_links_count is
too small, then it's possible that when unlinking that file, i_nlink
will already be zero.  Previously we were working around this kind of
corruption by forcing i_nlink to one; but we were doing this before
trying to delete the directory entry --- and if the file system is
corrupted enough that ext4_delete_entry() fails, then we exit with
i_nlink elevated, and this causes the orphan inode list handling to be
FUBAR'ed, such that when we unmount the file system, the orphan inode
list can get corrupted.

A better way to fix this is to simply skip trying to call drop_nlink()
if i_nlink is already zero, thus moving the check to the place where
it makes the most sense.

https://bugzilla.kernel.org/show_bug.cgi?id=205433

Link: https://lore.kernel.org/r/20191112032903.8828-1-tytso@mit.edu
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext4/namei.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 212b01861d941..b4e0c270def4a 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3065,18 +3065,17 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
 	if (IS_DIRSYNC(dir))
 		ext4_handle_sync(handle);
 
-	if (inode->i_nlink == 0) {
-		ext4_warning_inode(inode, "Deleting file '%.*s' with no links",
-				   dentry->d_name.len, dentry->d_name.name);
-		set_nlink(inode, 1);
-	}
 	retval = ext4_delete_entry(handle, dir, de, bh);
 	if (retval)
 		goto end_unlink;
 	dir->i_ctime = dir->i_mtime = current_time(dir);
 	ext4_update_dx_flag(dir);
 	ext4_mark_inode_dirty(handle, dir);
-	drop_nlink(inode);
+	if (inode->i_nlink == 0)
+		ext4_warning_inode(inode, "Deleting file '%.*s' with no links",
+				   dentry->d_name.len, dentry->d_name.name);
+	else
+		drop_nlink(inode);
 	if (!inode->i_nlink)
 		ext4_orphan_add(handle, inode);
 	inode->i_ctime = current_time(inode);
-- 
2.20.1