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Date: Tue, 25 Jun 2024 13:00:28 +0200
From: Mateusz Guzik <mjguzik@...il.com>
To: brauner@...nel.org
Cc: viro@...iv.linux.org.uk,
jack@...e.cz,
linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org,
io-uring@...r.kernel.org,
axboe@...nel.dk,
torvalds@...ux-foundation.org,
xry111@...111.site,
loongarch@...ts.linux.dev,
Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH 2/2] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)
The newly used helper also checks for 0-sized buffers.
This avoids path lookup code, lockref management, memory allocation and
in case of NULL path userspace memory access (which can be quite
expensive with SMAP on x86_64).
statx with AT_EMPTY_PATH paired with "" or NULL argument as appropriate
issued on Sapphire Rapids (ops/s):
stock: 4231237
0-check: 5944063 (+40%)
NULL path: 6601619 (+11%/+56%)
Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---
fs/internal.h | 2 ++
fs/stat.c | 90 ++++++++++++++++++++++++++++++++++--------------
io_uring/statx.c | 23 +++++++------
3 files changed, 80 insertions(+), 35 deletions(-)
diff --git a/fs/internal.h b/fs/internal.h
index 1caa6a8f666f..0a018ebcaf49 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -244,6 +244,8 @@ extern const struct dentry_operations ns_dentry_operations;
int getname_statx_lookup_flags(int flags);
int do_statx(int dfd, struct filename *filename, unsigned int flags,
unsigned int mask, struct statx __user *buffer);
+int do_statx_fd(int fd, unsigned int flags, unsigned int mask,
+ struct statx __user *buffer);
/*
* fs/splice.c:
diff --git a/fs/stat.c b/fs/stat.c
index 106684034fdb..1214826f3a36 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -214,6 +214,43 @@ int getname_statx_lookup_flags(int flags)
return lookup_flags;
}
+static int vfs_statx_path(struct path *path, int flags, struct kstat *stat,
+ u32 request_mask)
+{
+ int error = vfs_getattr(path, stat, request_mask, flags);
+
+ if (request_mask & STATX_MNT_ID_UNIQUE) {
+ stat->mnt_id = real_mount(path->mnt)->mnt_id_unique;
+ stat->result_mask |= STATX_MNT_ID_UNIQUE;
+ } else {
+ stat->mnt_id = real_mount(path->mnt)->mnt_id;
+ stat->result_mask |= STATX_MNT_ID;
+ }
+
+ if (path->mnt->mnt_root == path->dentry)
+ stat->attributes |= STATX_ATTR_MOUNT_ROOT;
+ stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;
+
+ /* Handle STATX_DIOALIGN for block devices. */
+ if (request_mask & STATX_DIOALIGN) {
+ struct inode *inode = d_backing_inode(path->dentry);
+
+ if (S_ISBLK(inode->i_mode))
+ bdev_statx_dioalign(inode, stat);
+ }
+
+ return error;
+}
+
+static int vfs_statx_fd(int fd, int flags, struct kstat *stat,
+ u32 request_mask)
+{
+ CLASS(fd_raw, f)(fd);
+ if (!f.file)
+ return -EBADF;
+ return vfs_statx_path(&f.file->f_path, flags, stat, request_mask);
+}
+
/**
* vfs_statx - Get basic and extra attributes by filename
* @dfd: A file descriptor representing the base dir for a relative filename
@@ -243,36 +280,13 @@ static int vfs_statx(int dfd, struct filename *filename, int flags,
retry:
error = filename_lookup(dfd, filename, lookup_flags, &path, NULL);
if (error)
- goto out;
-
- error = vfs_getattr(&path, stat, request_mask, flags);
-
- if (request_mask & STATX_MNT_ID_UNIQUE) {
- stat->mnt_id = real_mount(path.mnt)->mnt_id_unique;
- stat->result_mask |= STATX_MNT_ID_UNIQUE;
- } else {
- stat->mnt_id = real_mount(path.mnt)->mnt_id;
- stat->result_mask |= STATX_MNT_ID;
- }
-
- if (path.mnt->mnt_root == path.dentry)
- stat->attributes |= STATX_ATTR_MOUNT_ROOT;
- stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;
-
- /* Handle STATX_DIOALIGN for block devices. */
- if (request_mask & STATX_DIOALIGN) {
- struct inode *inode = d_backing_inode(path.dentry);
-
- if (S_ISBLK(inode->i_mode))
- bdev_statx_dioalign(inode, stat);
- }
-
+ return error;
+ error = vfs_statx_path(&path, flags, stat, request_mask);
path_put(&path);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
-out:
return error;
}
@@ -677,6 +691,29 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags,
return cp_statx(&stat, buffer);
}
+int do_statx_fd(int fd, unsigned int flags, unsigned int mask,
+ struct statx __user *buffer)
+{
+ struct kstat stat;
+ int error;
+
+ if (mask & STATX__RESERVED)
+ return -EINVAL;
+ if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
+ return -EINVAL;
+
+ /* STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests
+ * from userland.
+ */
+ mask &= ~STATX_CHANGE_COOKIE;
+
+ error = vfs_statx_fd(fd, flags, &stat, mask);
+ if (error)
+ return error;
+
+ return cp_statx(&stat, buffer);
+}
+
/**
* sys_statx - System call to get enhanced stats
* @dfd: Base directory to pathwalk from *or* fd to stat.
@@ -696,6 +733,9 @@ SYSCALL_DEFINE5(statx,
int ret;
struct filename *name;
+ if (flags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
+ return do_statx_fd(dfd, flags, mask, buffer);
+
name = getname_flags(filename, getname_statx_lookup_flags(flags), NULL);
ret = do_statx(dfd, name, flags, mask, buffer);
putname(name);
diff --git a/io_uring/statx.c b/io_uring/statx.c
index abb874209caa..fe967ecb1762 100644
--- a/io_uring/statx.c
+++ b/io_uring/statx.c
@@ -23,6 +23,7 @@ struct io_statx {
int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_statx *sx = io_kiocb_to_cmd(req, struct io_statx);
+ struct filename *filename;
const char __user *path;
if (sqe->buf_index || sqe->splice_fd_in)
@@ -36,15 +37,14 @@ int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
sx->buffer = u64_to_user_ptr(READ_ONCE(sqe->addr2));
sx->flags = READ_ONCE(sqe->statx_flags);
- sx->filename = getname_flags(path,
- getname_statx_lookup_flags(sx->flags),
- NULL);
-
- if (IS_ERR(sx->filename)) {
- int ret = PTR_ERR(sx->filename);
-
- sx->filename = NULL;
- return ret;
+ sx->filename = NULL;
+ if (!(sx->flags == AT_EMPTY_PATH && vfs_empty_path(sx->dfd, path))) {
+ filename = getname_flags(path,
+ getname_statx_lookup_flags(sx->flags),
+ NULL);
+ if (IS_ERR(filename))
+ return PTR_ERR(filename);
+ sx->filename = filename;
}
req->flags |= REQ_F_NEED_CLEANUP;
@@ -59,7 +59,10 @@ int io_statx(struct io_kiocb *req, unsigned int issue_flags)
WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
- ret = do_statx(sx->dfd, sx->filename, sx->flags, sx->mask, sx->buffer);
+ if (sx->filename == NULL)
+ ret = do_statx_fd(sx->dfd, sx->flags, sx->mask, sx->buffer);
+ else
+ ret = do_statx(sx->dfd, sx->filename, sx->flags, sx->mask, sx->buffer);
io_req_set_res(req, ret, 0);
return IOU_OK;
}
--
2.43.0
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