This is a note to let you know that I've just added the patch titled
ext4: fix off-by-one on max nr_pages in ext4_find_unwritten_pgoff()
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: ext4-fix-off-by-one-on-max-nr_pages-in-ext4_find_unwritten_pgoff.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Mon Apr 9 17:09:24 CEST 2018
From: Eryu Guan eguan@redhat.com Date: Wed, 24 May 2017 18:02:20 -0400 Subject: ext4: fix off-by-one on max nr_pages in ext4_find_unwritten_pgoff()
From: Eryu Guan eguan@redhat.com
[ Upstream commit 624327f8794704c5066b11a52f9da6a09dce7f9a ]
ext4_find_unwritten_pgoff() is used to search for offset of hole or data in page range [index, end] (both inclusive), and the max number of pages to search should be at least one, if end == index. Otherwise the only page is missed and no hole or data is found, which is not correct.
When block size is smaller than page size, this can be demonstrated by preallocating a file with size smaller than page size and writing data to the last block. E.g. run this xfs_io command on a 1k block size ext4 on x86_64 host.
# xfs_io -fc "falloc 0 3k" -c "pwrite 2k 1k" \ -c "seek -d 0" /mnt/ext4/testfile wrote 1024/1024 bytes at offset 2048 1 KiB, 1 ops; 0.0000 sec (42.459 MiB/sec and 43478.2609 ops/sec) Whence Result DATA EOF
Data at offset 2k was missed, and lseek(2) returned ENXIO.
This is unconvered by generic/285 subtest 07 and 08 on ppc64 host, where pagesize is 64k. Because a recent change to generic/285 reduced the preallocated file size to smaller than 64k.
Signed-off-by: Eryu Guan eguan@redhat.com Signed-off-by: Theodore Ts'o tytso@mit.edu Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -429,7 +429,7 @@ static int ext4_find_unwritten_pgoff(str int i, num; unsigned long nr_pages;
- num = min_t(pgoff_t, end - index, PAGEVEC_SIZE); + num = min_t(pgoff_t, end - index, PAGEVEC_SIZE - 1) + 1; nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index, (pgoff_t)num); if (nr_pages == 0)
Patches currently in stable-queue which might be from eguan@redhat.com are
queue-4.9/ext4-fix-off-by-one-on-max-nr_pages-in-ext4_find_unwritten_pgoff.patch