+ vfs-partially-revert-dont-allow-writes-to-swap-files.patch added to -mm tree

+ vfs-partially-revert-dont-allow-writes-to-swap-files.patch added to -mm tree

[akpm]

The patch titled
     Subject: vfs: partially revert "don't allow writes to swap files"
has been added to the -mm tree.  Its filename is
     vfs-partially-revert-dont-allow-writes-to-swap-files.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/vfs-partially-revert-dont-allow-writes-to-swap-files.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/vfs-partially-revert-dont-allow-writes-to-swap-files.patch

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------------------------------------------------------
From: Darrick J. Wong <darrick.wong@oracle.com>
Subject: vfs: partially revert "don't allow writes to swap files"

In commit dc617f29dbe5 ("vfs: don't allow writes to swap files") we tried
to prevent userspace programs from writing to active swap devices. 
However, it turns out that userspace hibernation requires the ability to
write the hibernation image to a swap device, so revert the write path
checks.

Link: http://lkml.kernel.org/r/20200303191023.GD8037@magnolia
Fixes: dc617f29dbe5 ("vfs: don't allow writes to swap files")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reported-by: Domenico Andreoli <domenico.andreoli@linux.com>
Reported-by: Marian Klein <mkleinsoft@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/block_dev.c |    3 ---
 mm/filemap.c   |    3 ---
 mm/memory.c    |    4 ----
 mm/mmap.c      |    8 ++------
 4 files changed, 2 insertions(+), 16 deletions(-)

--- a/fs/block_dev.c~vfs-partially-revert-dont-allow-writes-to-swap-files
+++ a/fs/block_dev.c
@@ -2001,9 +2001,6 @@ ssize_t blkdev_write_iter(struct kiocb *
 	if (bdev_read_only(I_BDEV(bd_inode)))
 		return -EPERM;
 
-	if (IS_SWAPFILE(bd_inode))
-		return -ETXTBSY;
-
 	if (!iov_iter_count(from))
 		return 0;
 
--- a/mm/filemap.c~vfs-partially-revert-dont-allow-writes-to-swap-files
+++ a/mm/filemap.c
@@ -2920,9 +2920,6 @@ inline ssize_t generic_write_checks(stru
 	loff_t count;
 	int ret;
 
-	if (IS_SWAPFILE(inode))
-		return -ETXTBSY;
-
 	if (!iov_iter_count(from))
 		return 0;
 
--- a/mm/memory.c~vfs-partially-revert-dont-allow-writes-to-swap-files
+++ a/mm/memory.c
@@ -2376,10 +2376,6 @@ static vm_fault_t do_page_mkwrite(struct
 
 	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
 
-	if (vmf->vma->vm_file &&
-	    IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host))
-		return VM_FAULT_SIGBUS;