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From: Eric Biggers <ebiggers@kernel.org>
To: linux-fsdevel@vger.kernel.org
Cc: linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	Theodore Ts'o <tytso@mit.edu>, Christoph Hellwig <hch@lst.de>,
	stable@vger.kernel.org, Jan Kara <jack@suse.cz>
Subject: [PATCH v2 01/12] fs: fix lazytime expiration handling in __writeback_single_inode()
Date: Fri,  8 Jan 2021 23:58:52 -0800	[thread overview]
Message-ID: <20210109075903.208222-2-ebiggers@kernel.org> (raw)
In-Reply-To: <20210109075903.208222-1-ebiggers@kernel.org>

From: Eric Biggers <ebiggers@google.com>

When lazytime is enabled and an inode is being written due to its
in-memory updated timestamps having expired, either due to a sync() or
syncfs() system call or due to dirtytime_expire_interval having elapsed,
the VFS needs to inform the filesystem so that the filesystem can copy
the inode's timestamps out to the on-disk data structures.

This is done by __writeback_single_inode() calling
mark_inode_dirty_sync(), which then calls ->dirty_inode(I_DIRTY_SYNC).

However, this occurs after __writeback_single_inode() has already
cleared the dirty flags from ->i_state.  This causes two bugs:

- mark_inode_dirty_sync() redirties the inode, causing it to remain
  dirty.  This wastefully causes the inode to be written twice.  But
  more importantly, it breaks cases where sync_filesystem() is expected
  to clean dirty inodes.  This includes the FS_IOC_REMOVE_ENCRYPTION_KEY
  ioctl (as reported at
  https://lore.kernel.org/r/20200306004555.GB225345@gmail.com), as well
  as possibly filesystem freezing (freeze_super()).

- Since ->i_state doesn't contain I_DIRTY_TIME when ->dirty_inode() is
  called from __writeback_single_inode() for lazytime expiration,
  xfs_fs_dirty_inode() ignores the notification.  (XFS only cares about
  lazytime expirations, and it assumes that I_DIRTY_TIME will contain
  i_state during those.)  Therefore, lazy timestamps aren't persisted by
  sync(), syncfs(), or dirtytime_expire_interval on XFS.

Fix this by moving the call to mark_inode_dirty_sync() to earlier in
__writeback_single_inode(), before the dirty flags are cleared from
i_state.  This makes filesystems be properly notified of the timestamp
expiration, and it avoids incorrectly redirtying the inode.

This fixes xfstest generic/580 (which tests
FS_IOC_REMOVE_ENCRYPTION_KEY) when run on ext4 or f2fs with lazytime
enabled.  It also fixes the new lazytime xfstest I've proposed, which
reproduces the above-mentioned XFS bug
(https://lore.kernel.org/r/20210105005818.92978-1-ebiggers@kernel.org).

Alternatively, we could call ->dirty_inode(I_DIRTY_SYNC) directly.  But
due to the introduction of I_SYNC_QUEUED, mark_inode_dirty_sync() is the
right thing to do because mark_inode_dirty_sync() now knows not to move
the inode to a writeback list if it is currently queued for sync.

Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option")
Cc: stable@vger.kernel.org
Depends-on: 5afced3bf281 ("writeback: Avoid skipping inode writeback")
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/fs-writeback.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index acfb55834af23..c41cb887eb7d3 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1474,21 +1474,25 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 	}
 
 	/*
-	 * Some filesystems may redirty the inode during the writeback
-	 * due to delalloc, clear dirty metadata flags right before
-	 * write_inode()
+	 * If the inode has dirty timestamps and we need to write them, call
+	 * mark_inode_dirty_sync() to notify the filesystem about it and to
+	 * change I_DIRTY_TIME into I_DIRTY_SYNC.
 	 */
-	spin_lock(&inode->i_lock);
-
-	dirty = inode->i_state & I_DIRTY;
 	if ((inode->i_state & I_DIRTY_TIME) &&
-	    ((dirty & I_DIRTY_INODE) ||
-	     wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
+	    (wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
 	     time_after(jiffies, inode->dirtied_time_when +
 			dirtytime_expire_interval * HZ))) {
-		dirty |= I_DIRTY_TIME;
 		trace_writeback_lazytime(inode);
+		mark_inode_dirty_sync(inode);
 	}
+
+	/*
+	 * Some filesystems may redirty the inode during the writeback
+	 * due to delalloc, clear dirty metadata flags right before
+	 * write_inode()
+	 */
+	spin_lock(&inode->i_lock);
+	dirty = inode->i_state & I_DIRTY;
 	inode->i_state &= ~dirty;
 
 	/*
@@ -1509,8 +1513,6 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 
 	spin_unlock(&inode->i_lock);
 
-	if (dirty & I_DIRTY_TIME)
-		mark_inode_dirty_sync(inode);
 	/* Don't write the inode if only I_DIRTY_PAGES was set */
 	if (dirty & ~I_DIRTY_PAGES) {
 		int err = write_inode(inode, wbc);
-- 
2.30.0


WARNING: multiple messages have this Message-ID
From: Eric Biggers <ebiggers@kernel.org>
To: linux-fsdevel@vger.kernel.org
Cc: Theodore Ts'o <tytso@mit.edu>,
	stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net,
	linux-xfs@vger.kernel.org, Jan Kara <jack@suse.cz>,
	linux-ext4@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: [f2fs-dev] [PATCH v2 01/12] fs: fix lazytime expiration handling in __writeback_single_inode()
Date: Fri,  8 Jan 2021 23:58:52 -0800	[thread overview]
Message-ID: <20210109075903.208222-2-ebiggers@kernel.org> (raw)
In-Reply-To: <20210109075903.208222-1-ebiggers@kernel.org>

From: Eric Biggers <ebiggers@google.com>

When lazytime is enabled and an inode is being written due to its
in-memory updated timestamps having expired, either due to a sync() or
syncfs() system call or due to dirtytime_expire_interval having elapsed,
the VFS needs to inform the filesystem so that the filesystem can copy
the inode's timestamps out to the on-disk data structures.

This is done by __writeback_single_inode() calling
mark_inode_dirty_sync(), which then calls ->dirty_inode(I_DIRTY_SYNC).

However, this occurs after __writeback_single_inode() has already
cleared the dirty flags from ->i_state.  This causes two bugs:

- mark_inode_dirty_sync() redirties the inode, causing it to remain
  dirty.  This wastefully causes the inode to be written twice.  But
  more importantly, it breaks cases where sync_filesystem() is expected
  to clean dirty inodes.  This includes the FS_IOC_REMOVE_ENCRYPTION_KEY
  ioctl (as reported at
  https://lore.kernel.org/r/20200306004555.GB225345@gmail.com), as well
  as possibly filesystem freezing (freeze_super()).

- Since ->i_state doesn't contain I_DIRTY_TIME when ->dirty_inode() is
  called from __writeback_single_inode() for lazytime expiration,
  xfs_fs_dirty_inode() ignores the notification.  (XFS only cares about
  lazytime expirations, and it assumes that I_DIRTY_TIME will contain
  i_state during those.)  Therefore, lazy timestamps aren't persisted by
  sync(), syncfs(), or dirtytime_expire_interval on XFS.

Fix this by moving the call to mark_inode_dirty_sync() to earlier in
__writeback_single_inode(), before the dirty flags are cleared from
i_state.  This makes filesystems be properly notified of the timestamp
expiration, and it avoids incorrectly redirtying the inode.

This fixes xfstest generic/580 (which tests
FS_IOC_REMOVE_ENCRYPTION_KEY) when run on ext4 or f2fs with lazytime
enabled.  It also fixes the new lazytime xfstest I've proposed, which
reproduces the above-mentioned XFS bug
(https://lore.kernel.org/r/20210105005818.92978-1-ebiggers@kernel.org).

Alternatively, we could call ->dirty_inode(I_DIRTY_SYNC) directly.  But
due to the introduction of I_SYNC_QUEUED, mark_inode_dirty_sync() is the
right thing to do because mark_inode_dirty_sync() now knows not to move
the inode to a writeback list if it is currently queued for sync.

Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option")
Cc: stable@vger.kernel.org
Depends-on: 5afced3bf281 ("writeback: Avoid skipping inode writeback")
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/fs-writeback.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index acfb55834af23..c41cb887eb7d3 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1474,21 +1474,25 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 	}
 
 	/*
-	 * Some filesystems may redirty the inode during the writeback
-	 * due to delalloc, clear dirty metadata flags right before
-	 * write_inode()
+	 * If the inode has dirty timestamps and we need to write them, call
+	 * mark_inode_dirty_sync() to notify the filesystem about it and to
+	 * change I_DIRTY_TIME into I_DIRTY_SYNC.
 	 */
-	spin_lock(&inode->i_lock);
-
-	dirty = inode->i_state & I_DIRTY;
 	if ((inode->i_state & I_DIRTY_TIME) &&
-	    ((dirty & I_DIRTY_INODE) ||
-	     wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
+	    (wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
 	     time_after(jiffies, inode->dirtied_time_when +
 			dirtytime_expire_interval * HZ))) {
-		dirty |= I_DIRTY_TIME;
 		trace_writeback_lazytime(inode);
+		mark_inode_dirty_sync(inode);
 	}
+
+	/*
+	 * Some filesystems may redirty the inode during the writeback
+	 * due to delalloc, clear dirty metadata flags right before
+	 * write_inode()
+	 */
+	spin_lock(&inode->i_lock);
+	dirty = inode->i_state & I_DIRTY;
 	inode->i_state &= ~dirty;
 
 	/*
@@ -1509,8 +1513,6 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 
 	spin_unlock(&inode->i_lock);
 
-	if (dirty & I_DIRTY_TIME)
-		mark_inode_dirty_sync(inode);
 	/* Don't write the inode if only I_DIRTY_PAGES was set */
 	if (dirty & ~I_DIRTY_PAGES) {
 		int err = write_inode(inode, wbc);
-- 
2.30.0



_______________________________________________
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https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

  reply	other threads:[~2021-01-09  8:00 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-09  7:58 [PATCH v2 00/12] lazytime fix and cleanups Eric Biggers
2021-01-09  7:58 ` [f2fs-dev] " Eric Biggers
2021-01-09  7:58 ` Eric Biggers [this message]
2021-01-09  7:58   ` [f2fs-dev] [PATCH v2 01/12] fs: fix lazytime expiration handling in __writeback_single_inode() Eric Biggers
2021-01-11 10:48   ` Christoph Hellwig
2021-01-11 10:48     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 14:46   ` Jan Kara
2021-01-11 14:46     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 02/12] fs: correctly document the inode dirty flags Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:48   ` Jan Kara
2021-01-11 14:48     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 03/12] fs: only specify I_DIRTY_TIME when needed in generic_update_time() Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:50   ` Jan Kara
2021-01-11 14:50     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 04/12] fat: only specify I_DIRTY_TIME when needed in fat_update_time() Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:52   ` Christoph Hellwig
2021-01-11 10:52     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 19:50     ` Eric Biggers
2021-01-11 19:50       ` [f2fs-dev] " Eric Biggers
2021-01-12  5:21       ` Dave Chinner
2021-01-12  5:21         ` [f2fs-dev] " Dave Chinner
2021-01-12 13:23       ` Christoph Hellwig
2021-01-12 13:23         ` [f2fs-dev] " Christoph Hellwig
2021-01-11 14:52   ` Jan Kara
2021-01-11 14:52     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 05/12] fs: don't call ->dirty_inode for lazytime timestamp updates Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:54   ` Jan Kara
2021-01-11 14:54     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 06/12] fs: pass only I_DIRTY_INODE flags to ->dirty_inode Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:56   ` Jan Kara
2021-01-11 14:56     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 07/12] fs: clean up __mark_inode_dirty() a bit Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:59   ` Jan Kara
2021-01-11 14:59     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 08/12] fs: drop redundant check from __writeback_single_inode() Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:52   ` Christoph Hellwig
2021-01-11 10:52     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 15:00   ` Jan Kara
2021-01-11 15:00     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 09/12] fs: improve comments for writeback_single_inode() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:53   ` Christoph Hellwig
2021-01-11 10:53     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 15:05   ` Jan Kara
2021-01-11 15:05     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 10/12] gfs2: don't worry about I_DIRTY_TIME in gfs2_fsync() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-11 15:06   ` Jan Kara
2021-01-11 15:06     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 11/12] ext4: simplify i_state checks in __ext4_update_other_inode_time() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:53   ` Christoph Hellwig
2021-01-11 10:53     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 20:23     ` Eric Biggers
2021-01-11 20:23       ` [f2fs-dev] " Eric Biggers
2021-01-12 13:25       ` Christoph Hellwig
2021-01-12 13:25         ` [f2fs-dev] " Christoph Hellwig
2021-02-03  5:16         ` Theodore Ts'o
2021-02-03  5:16           ` [f2fs-dev] " Theodore Ts'o
2021-01-11 15:11   ` Jan Kara
2021-01-11 15:11     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 12/12] xfs: remove a stale comment from xfs_file_aio_write_checks() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-12 17:31   ` Darrick J. Wong
2021-01-12 17:31     ` [f2fs-dev] " Darrick J. Wong
2021-01-11 15:15 ` [PATCH v2 00/12] lazytime fix and cleanups Jan Kara
2021-01-11 15:15   ` [f2fs-dev] " Jan Kara
2021-01-11 20:44   ` Eric Biggers
2021-01-11 20:44     ` [f2fs-dev] " Eric Biggers
2021-02-03  5:11     ` Theodore Ts'o
2021-02-03  5:11       ` [f2fs-dev] " Theodore Ts'o
2021-02-03  5:22       ` Eric Biggers
2021-02-03  5:22         ` [f2fs-dev] " Eric Biggers
2021-02-03 15:49         ` Theodore Ts'o
2021-02-03 15:49           ` [f2fs-dev] " Theodore Ts'o

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