Patch "ext4: fix interaction between i_size, fallocate, and delalloc after a crash" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

ext4: fix interaction between i_size, fallocate, and delalloc after a crash

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ext4-fix-interaction-between-i_size-fallocate-and-delalloc-after-a-crash.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Theodore Ts'o <[email protected]>
Date: Fri, 6 Oct 2017 23:09:55 -0400
Subject: ext4: fix interaction between i_size, fallocate, and delalloc after a crash

From: Theodore Ts'o <[email protected]>

commit 51e3ae81ec58e95f10a98ef3dd6d7bce5d8e35a2 upstream.

If there are pending writes subject to delayed allocation, then i_size will show size after the writes have completed, while i_disksize contains the value of i_size on the disk (since the writes have not been persisted to disk).

If fallocate(2) is called with the FALLOC_FL_KEEP_SIZE flag, either with or without the FALLOC_FL_ZERO_RANGE flag set, and the new size after the fallocate(2) is between i_size and i_disksize, then after a crash, if a journal commit has resulted in the changes made by the fallocate() call to be persisted after a crash, but the delayed allocation write has not resolved itself, i_size would not be updated, and this would cause the following e2fsck complaint:

Inode 12, end of extent exceeds allowed value

	(logical block 33, physical block 33441, len 7)

This can only take place on a sparse file, where the fallocate(2) call is allocating blocks in a range which is before a pending delayed allocation write which is extending i_size. Since this situation is quite rare, and the window in which the crash must take place is typically < 30 seconds, in practice this condition will rarely happen.

Nevertheless, it can be triggered in testing, and in particular by xfstests generic/456.

---
 fs/ext4/extents.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -4794,7 +4794,8 @@ static long ext4_zero_range(struct file
 	}
 
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
-	     offset + len > i_size_read(inode)) {
+	    (offset + len > i_size_read(inode) ||
+	     offset + len > EXT4_I(inode)->i_disksize)) {
 		new_size = offset + len;
 		ret = inode_newsize_ok(inode, new_size);
 		if (ret)

@@ -4965,7 +4966,8 @@ long ext4_fallocate(struct file *file, i
 	}
 
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
-	     offset + len > i_size_read(inode)) {
+	    (offset + len > i_size_read(inode) ||
+	     offset + len > EXT4_I(inode)->i_disksize)) {
 		new_size = offset + len;
 		ret = inode_newsize_ok(inode, new_size);
 		if (ret)

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/fscrypt-lock-mutex-before-checking-for-bounce-page-pool.patch queue-4.14/ext4-prevent-data-corruption-with-journaling-dax.patch queue-4.14/ext4-prevent-data-corruption-with-inline-data-dax.patch queue-4.14/ext4-fix-interaction-between-i_size-fallocate-and-delalloc-after-a-crash.patch