On Wed, Nov 23, 2022 at 11:43:36AM +0100, Miklos Szeredi wrote:
> file_modified() must be called with inode lock held. fuse_fallocate()
> didn't lock the inode in case of just FALLOC_KEEP_SIZE flags value, which
> resulted in a kernel Warning in notify_change().
>
> Lock the inode unconditionally, like all other fallocate implementations
> do.
>
> Reported-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
> Reported-and-tested-by: syzbot+462da39f0667b357c4b6@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 4a6f278d4827 ("fuse: add file_modified() to fallocate")
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
> ---
> fs/fuse/file.c | 37 ++++++++++++++++---------------------
> 1 file changed, 16 insertions(+), 21 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 71bfb663aac5..89f4741728ba 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2963,11 +2963,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
> .mode = mode
> };
> int err;
> - bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) ||
> - (mode & (FALLOC_FL_PUNCH_HOLE |
> - FALLOC_FL_ZERO_RANGE));
> -
> - bool block_faults = FUSE_IS_DAX(inode) && lock_inode;
> + bool block_faults = FUSE_IS_DAX(inode) &&
> + (!(mode & FALLOC_FL_KEEP_SIZE) ||
> + (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)));
Hi Miklos,
I think that we probably don't need above tests for "block_faults".
Initially, ideas was that I wanted to synchronize truncate/punch_hole
with fault handler path. Fuse did not seem to do it, so I decided to
add it only for fuse DAX code to begin with. Details are in following
commit.
commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f
Author: Vivek Goyal <vgoyal@xxxxxxxxxx>
Date: Wed Aug 19 18:19:54 2020 -0400
virtiofs: serialize truncate/punch_hole and dax fault path
I wanted to take following two locks for it to work.
inode_lock(inode)
down_write(&fi->i_mmap_sem);
And that's why following condition.
bool block_faults = FUSE_IS_DAX(inode) && lock_inode;
Given that we will now always take inode lock, we could just do.
bool block_faults = FUSE_IS_DAX(inode); instead. Not sure is there really
a benefit in going through different "mode" flags and make this condition
even narrower.
I see that now fi->i_mmap_sem has been replaced by
filemap_invalidate_lock(inode->i_mapping).
At some point of time we should review fuse fault code and see if that
code need to serialize with truncate/punch_hole path as well. If answer
is yes, then we could get rid of this "block_faults" altogether and
always take inode->i_mapping lock in truncate path.
IOW, I think we should be able to simplify above to just for now.
bool block_faults = FUSE_IS_DAX(inode);
Thanks
Vivek
>
> if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
> FALLOC_FL_ZERO_RANGE))
> @@ -2976,22 +2974,20 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
> if (fm->fc->no_fallocate)
> return -EOPNOTSUPP;
>
> - if (lock_inode) {
> - inode_lock(inode);
> - if (block_faults) {
> - filemap_invalidate_lock(inode->i_mapping);
> - err = fuse_dax_break_layouts(inode, 0, 0);
> - if (err)
> - goto out;
> - }
> + inode_lock(inode);
> + if (block_faults) {
> + filemap_invalidate_lock(inode->i_mapping);
> + err = fuse_dax_break_layouts(inode, 0, 0);
> + if (err)
> + goto out;
> + }
>
> - if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) {
> - loff_t endbyte = offset + length - 1;
> + if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) {
> + loff_t endbyte = offset + length - 1;
>
> - err = fuse_writeback_range(inode, offset, endbyte);
> - if (err)
> - goto out;
> - }
> + err = fuse_writeback_range(inode, offset, endbyte);
> + if (err)
> + goto out;
> }
>
> if (!(mode & FALLOC_FL_KEEP_SIZE) &&
> @@ -3039,8 +3035,7 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
> if (block_faults)
> filemap_invalidate_unlock(inode->i_mapping);
>
> - if (lock_inode)
> - inode_unlock(inode);
> + inode_unlock(inode);
>
> fuse_flush_time_update(inode);
>
> --
> 2.38.1
>
