Enabling FUSE passthrough for mmap-ed operations not only affects performance, but has also been shown as mandatory for the correct functioning of FUSE passthrough. yanwu noticed [1] that a FUSE file with passthrough enabled may suffer data inconsistencies if the same file is also accessed with mmap. What happens is that read/write operations are directly applied to the backing file's page cache, while mmap-ed operations are affecting the FUSE file's page cache. Extend the FUSE passthrough implementation to also handle memory-mapped FUSE file, to both fix the cache inconsistencies and extend the passthrough performance benefits to mmap-ed operations. [1] https://lore.kernel.org/lkml/20210119110654.11817-1-wu-yan@xxxxxxx/ Signed-off-by: Alessio Balsini <balsini@xxxxxxxxxxx> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- fs/fuse/file.c | 3 +++ fs/fuse/fuse_i.h | 1 + fs/fuse/passthrough.c | 16 ++++++++++++++++ 3 files changed, 20 insertions(+) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index d6fc99245a61..bae1137426a9 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2499,6 +2499,9 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma) if (FUSE_IS_DAX(file_inode(file))) return fuse_dax_mmap(file, vma); + if (fuse_file_passthrough(ff)) + return fuse_passthrough_mmap(file, vma); + if (ff->open_flags & FOPEN_DIRECT_IO) { /* Can't provide the coherency needed for MAP_SHARED * if FUSE_DIRECT_IO_RELAX isn't set. diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 7dd770efceba..6fee4c33678f 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -1403,5 +1403,6 @@ ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos, ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags); +ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma); #endif /* _FS_FUSE_I_H */ diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c index fa5b41a4cdc1..a05280ceba83 100644 --- a/fs/fuse/passthrough.c +++ b/fs/fuse/passthrough.c @@ -148,6 +148,22 @@ ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe, return ret; } +ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct fuse_file *ff = file->private_data; + struct file *backing_file = fuse_file_passthrough(ff); + struct backing_file_ctx ctx = { + .cred = ff->cred, + .user_file = file, + .accessed = fuse_file_accessed, + }; + + pr_debug("%s: backing_file=0x%p, start=%lu, end=%lu\n", __func__, + backing_file, vma->vm_start, vma->vm_end); + + return backing_file_mmap(backing_file, vma, &ctx); +} + struct fuse_backing *fuse_backing_get(struct fuse_backing *fb) { if (fb && refcount_inc_not_zero(&fb->count)) -- 2.34.1
