Mike Yuan
5817c73391
name_to_handle_at_try_unique_mntid_fid() in its current form is ill-designed for various reasons: * AT_HANDLE_FID requires file system support, while unique mount id is a VFS concept hence is always available if supported. Hence the fallback for AT_HANDLE_MNT_ID_UNIQUE should be independent of fid. * The request for AT_HANDLE_MNT_ID_UNIQUE can be identified via specifying ret_unique_mnt_id, no need for opening up the control to caller (and currently the function simply doesn't handle mismatch between ret params and flags). * The caller cannot realistically differentiate whether the returned mount id is actually unique. * The path_get_unique_mnt_id() fallback did not handle AT_SYMLINK_FOLLOW. Let's instead move the statx() fallback into name_to_handle_at_loop() directly, and revamp interaction of ret_mnt_id/ret_unique_mnt_id: if both are set, it indicates that the caller can handle both, hence set what we have and return 0/1 for whether we managed to acquire the unique one. The !ret_handle && ret_mnt_id logic is removed. Let's not rely on undocumented bizaare behavior and it's unused anyways. path_get_mnt_id_at() exists for a reason...
91 lines
3.9 KiB
C
91 lines
3.9 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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#include "basic-forward.h"
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/* The limit used for /dev itself. 4MB should be enough since device nodes and symlinks don't
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* consume any space and udev isn't supposed to create regular file either. There's no limit on the
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* max number of inodes since such limit is hard to guess especially on large storage array
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* systems. */
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#define TMPFS_LIMITS_DEV ",size=4m"
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/* The limit used for /dev in private namespaces. 4MB for contents of regular files. The number of
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* inodes should be relatively low in private namespaces but for now use a 64k limit. */
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#define TMPFS_LIMITS_PRIVATE_DEV ",size=4m,nr_inodes=64k"
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/* Very little, if any use expected */
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#define TMPFS_LIMITS_EMPTY_OR_ALMOST ",size=4m,nr_inodes=1k"
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#define TMPFS_LIMITS_SYS TMPFS_LIMITS_EMPTY_OR_ALMOST
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/* On an extremely small device with only 256MB of RAM, 20% of RAM should be enough for the re-execution of
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* PID1 because 16MB of free space is required. */
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#define TMPFS_LIMITS_RUN ",size=20%,nr_inodes=800k"
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/* The limit used for various nested tmpfs mounts, in particular for guests started by systemd-nspawn.
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* 10% of RAM (using 16GB of RAM as a baseline) translates to 400k inodes (assuming 4k each) and 25%
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* translates to 1M inodes.
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* (On the host, /tmp is configured through a .mount unit file.) */
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#define NESTED_TMPFS_LIMITS ",size=10%,nr_inodes=400k"
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/* More space for volatile root and /var */
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#define TMPFS_LIMITS_VAR ",size=25%,nr_inodes=1m"
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#define TMPFS_LIMITS_ROOTFS TMPFS_LIMITS_VAR
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#define TMPFS_LIMITS_VOLATILE_STATE TMPFS_LIMITS_VAR
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bool is_name_to_handle_at_fatal_error(int err);
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int name_to_handle_at_loop(int fd, const char *path, struct file_handle **ret_handle, int *ret_mnt_id, uint64_t *ret_unique_mnt_id, int flags);
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int name_to_handle_at_try_fid(int fd, const char *path, struct file_handle **ret_handle, int *ret_mnt_id, uint64_t *ret_unique_mnt_id, int flags);
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int name_to_handle_at_u64(int fd, const char *path, uint64_t *ret);
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static inline int path_to_handle_u64(const char *path, uint64_t *ret) {
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return name_to_handle_at_u64(AT_FDCWD, path, ret);
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}
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static inline int fd_to_handle_u64(int fd, uint64_t *ret) {
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return name_to_handle_at_u64(fd, NULL, ret);
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}
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bool file_handle_equal(const struct file_handle *a, const struct file_handle *b);
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struct file_handle* file_handle_dup(const struct file_handle *fh);
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int path_get_mnt_id_at(int dir_fd, const char *path, int *ret);
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static inline int path_get_mnt_id(const char *path, int *ret) {
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return path_get_mnt_id_at(AT_FDCWD, path, ret);
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}
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int path_get_unique_mnt_id_at(int dir_fd, const char *path, uint64_t *ret);
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int is_mount_point_at(int dir_fd, const char *path, int flags);
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int path_is_mount_point_full(const char *path, const char *root, int flags);
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static inline int path_is_mount_point(const char *path) {
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return path_is_mount_point_full(path, NULL, 0);
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}
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bool fstype_is_network(const char *fstype);
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bool fstype_needs_quota(const char *fstype);
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bool fstype_is_api_vfs(const char *fstype);
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bool fstype_is_blockdev_backed(const char *fstype);
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bool fstype_is_ro(const char *fsype);
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bool fstype_can_discard(const char *fstype);
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bool fstype_can_uid_gid(const char *fstype);
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bool fstype_can_fmask_dmask(const char *fstype);
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const char* fstype_norecovery_option(const char *fstype);
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int dev_is_devtmpfs(void);
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int mount_nofollow(
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const char *source,
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const char *target,
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const char *filesystemtype,
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unsigned long mountflags,
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const void *data);
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const char* mount_propagation_flag_to_string(unsigned long flags);
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int mount_propagation_flag_from_string(const char *name, unsigned long *ret);
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bool mount_propagation_flag_is_valid(unsigned long flag);
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bool mount_new_api_supported(void);
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int mount_option_supported(const char *fstype, const char *key, const char *value);
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bool path_below_api_vfs(const char *p);
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