The existing process_init_reply() in fs/fuse/inode.c sets the ra_pages
value to the minimum of the max_readahead value provided by the user
and the pre-existing ra_pages value, which is initialized to
VM_READAHEAD_PAGES. This makes it impossible to increase the readahead
value to larger values.
Add a new flag which causes us to blindly accept the user-provided
value. Note that the existing read_ahead_kb sysfs entry for normal
block devices does the same (simply accepts user-provided values
directly with no checks).
Signed-off-by: Kevin Vigor <kvigor@xxxxxxxxx>
---
fs/fuse/inode.c | 8 ++++++--
include/uapi/linux/fuse.h | 3 +++
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 8b89e3ba7df3..81c96c404a76 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1182,8 +1182,12 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
fc->no_flock = 1;
}
- fm->sb->s_bdi->ra_pages =
+ if (arg->flags & FUSE_TRUST_MAX_RA) {
+ fm->sb->s_bdi->ra_pages = ra_pages;
+ } else {
+ fm->sb->s_bdi->ra_pages =
min(fm->sb->s_bdi->ra_pages, ra_pages);
+ }
fc->minor = arg->minor;
fc->max_write = arg->minor < 5 ? 4096 : arg->max_write;
fc->max_write = max_t(unsigned, 4096, fc->max_write);
@@ -1219,7 +1223,7 @@ void fuse_send_init(struct fuse_mount *fm)
FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
- FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT;
+ FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_TRUST_MAX_RA;
#ifdef CONFIG_FUSE_DAX
if (fm->fc->dax)
ia->in.flags |= FUSE_MAP_ALIGNMENT;
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index a1dc3ee1d17c..df9840f4642f 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -341,6 +341,8 @@ struct fuse_file_lock {
* write/truncate sgid is killed only if file has group
* execute permission. (Same as Linux VFS behavior).
* FUSE_SETXATTR_EXT: Server supports extended struct fuse_setxattr_in
+ * FUSE_TRUST_MAX_RA: Accept the user-provided max_readahead value instead
+ * of clamping to <= VM_READAHEAD_PAGES.
*/
#define FUSE_ASYNC_READ (1 << 0)
#define FUSE_POSIX_LOCKS (1 << 1)
@@ -372,6 +374,7 @@ struct fuse_file_lock {
#define FUSE_SUBMOUNTS (1 << 27)
#define FUSE_HANDLE_KILLPRIV_V2 (1 << 28)
#define FUSE_SETXATTR_EXT (1 << 29)
+#define FUSE_TRUST_MAX_RA (1 << 30)
/**
* CUSE INIT request/reply flags
--
2.33.1
