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fuse: handle extent map files in fuse_passthrough_fadvise()

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This addresses a collision between the pending backing_file fadvise
patch and the new extent-mapping code for famfs (which falls into the
passthrough bucket.

A file opened with FOPEN_PASSTHROUGH on an extent map backing has no
backing file: fuse_passthrough_open() returns before setting
ff->passthrough and ff->cred.  fuse_file_fadvise() routes every
FOPEN_PASSTHROUGH file to fuse_passthrough_fadvise(), which installed
the NULL ff->cred on the task with override_creds() and then passed the
NULL backing file to vfs_fadvise().  Any posix_fadvise(), readahead()
or madvise(MADV_WILLNEED) on such a file oopsed.  fio triggers it at
file open with its default invalidate and fadvise_hint settings.

Fall back to generic_fadvise() when there is no backing file, as the
other passthrough helpers fall back to their extent map or generic
implementations.  generic_fadvise() already ignores advice on DAX
inodes while keeping the EINVAL and ESPIPE checks.

Reported-by: Aravind Ramesh <arramesh@micron.com>
Fixes: 69f77a06ffad ("fuse: Forward vfs_fadvise to backing_file in passthrough mode")
Tested-by: John Groves <john@groves.net>
Signed-off-by: John Groves <john@groves.net>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
John Groves 2026-10-22 18:47:47 -05:00 committed by Miklos Szeredi
parent 5a9745611d
commit bf56861216
3 changed files with 7 additions and 3 deletions
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2
fs/fuse/file.c
View File

@ -3129,7 +3129,7 @@ static int fuse_file_fadvise(struct file *file, loff_t offset, loff_t len, int a
struct fuse_file *ff = file->private_data;
if (fuse_is_passthrough(ff))
return fuse_passthrough_fadvise(ff, offset, len, advice);
return fuse_passthrough_fadvise(file, offset, len, advice);
return generic_fadvise(file, offset, len, advice);
}

2
fs/fuse/fuse_i.h
View File

@ -1368,7 +1368,7 @@ 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);
int fuse_passthrough_fadvise(struct fuse_file *ff, loff_t offset, loff_t len, int advice);
int fuse_passthrough_fadvise(struct file *file, loff_t offset, loff_t len, int advice);
#ifdef CONFIG_SYSCTL
extern int fuse_sysctl_register(void);

6
fs/fuse/passthrough.c
View File

@ -159,12 +159,16 @@ ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma)
return backing_file_mmap(backing_file, vma, &ctx);
}
int fuse_passthrough_fadvise(struct fuse_file *ff, loff_t offset, loff_t len, int advice)
int fuse_passthrough_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
{
struct fuse_file *ff = file->private_data;
struct file *backing_file = fuse_file_passthrough(ff);
const struct cred *old_cred;
int ret;
if (!backing_file)
return generic_fadvise(file, offset, len, advice);
old_cred = override_creds(ff->cred);
ret = vfs_fadvise(backing_file, offset, len, advice);
revert_creds(old_cred);