The patch titled r/o bind mounts: stub functions has been removed from the -mm tree. Its filename was r-o-bind-mounts-stub-functions.patch This patch was dropped because an updated version will be merged ------------------------------------------------------ Subject: r/o bind mounts: stub functions From: Dave Hansen <haveblue@xxxxxxxxxx> This patch adds two function mnt_want_write() and mnt_drop_write(). These are used like a lock pair around and fs operations that might cause a write to the filesystem. Before these can become useful, we must first cover each place in the VFS where writes are performed with a want/drop pair. When that is complete, we can actually introduce code that will safely check the counts before allowing r/w<->r/o transitions to occur. Signed-off-by: Dave Hansen <haveblue@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/namespace.c | 54 ++++++++++++++++++++++++++++++++++++++++ include/linux/mount.h | 3 ++ 2 files changed, 57 insertions(+) diff -puN fs/namespace.c~r-o-bind-mounts-stub-functions fs/namespace.c --- a/fs/namespace.c~r-o-bind-mounts-stub-functions +++ a/fs/namespace.c @@ -80,6 +80,60 @@ struct vfsmount *alloc_vfsmnt(const char return mnt; } +/* + * Most r/o checks on a fs are for operations that take + * discrete amounts of time, like a write() or unlink(). + * We must keep track of when those operations start + * (for permission checks) and when they end, so that + * we can determine when writes are able to occur to + * a filesystem. + */ +/** + * mnt_want_write - get write access to a mount + * @mnt: the mount on which to take a write + * + * This tells the low-level filesystem that a write is + * about to be performed to it, and makes sure that + * writes are allowed before returning success. When + * the write operation is finished, mnt_drop_write() + * must be called. This is effectively a refcount. + */ +int mnt_want_write(struct vfsmount *mnt) +{ + if (__mnt_is_readonly(mnt)) + return -EROFS; + return 0; +} +EXPORT_SYMBOL_GPL(mnt_want_write); + +/** + * mnt_drop_write - give up write access to a mount + * @mnt: the mount on which to give up write access + * + * Tells the low-level filesystem that we are done + * performing writes to it. Must be matched with + * mnt_want_write() call above. + */ +void mnt_drop_write(struct vfsmount *mnt) +{ +} +EXPORT_SYMBOL_GPL(mnt_drop_write); + +/* + * __mnt_is_readonly: check whether a mount is read-only + * @mnt: the mount to check for its write status + * + * This shouldn't be used directly ouside of the VFS. + * It does not guarantee that the filesystem will stay + * r/w, just that it is right *now*. This can not and + * should not be used in place of IS_RDONLY(inode). + */ +int __mnt_is_readonly(struct vfsmount *mnt) +{ + return (mnt->mnt_sb->s_flags & MS_RDONLY); +} +EXPORT_SYMBOL_GPL(__mnt_is_readonly); + int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) { mnt->mnt_sb = sb; diff -puN include/linux/mount.h~r-o-bind-mounts-stub-functions include/linux/mount.h --- a/include/linux/mount.h~r-o-bind-mounts-stub-functions +++ a/include/linux/mount.h @@ -74,9 +74,12 @@ static inline struct vfsmount *mntget(st return mnt; } +extern int mnt_want_write(struct vfsmount *mnt); +extern void mnt_drop_write(struct vfsmount *mnt); extern void mntput_no_expire(struct vfsmount *mnt); extern void mnt_pin(struct vfsmount *mnt); extern void mnt_unpin(struct vfsmount *mnt); +extern int __mnt_is_readonly(struct vfsmount *mnt); static inline void mntput(struct vfsmount *mnt) { _ Patches currently in -mm which might be from haveblue@xxxxxxxxxx are markers-fix-warnings.patch maps4-add-proportional-set-size-accounting-in-smaps.patch maps4-rework-task_size-macros.patch maps4-move-is_swap_pte.patch maps4-introduce-a-generic-page-walker.patch maps4-use-pagewalker-in-clear_refs-and-smaps.patch maps4-simplify-interdependence-of-maps-and-smaps.patch maps4-move-clear_refs-code-to-task_mmuc.patch maps4-regroup-task_mmu-by-interface.patch maps4-add-proc-pid-pagemap-interface.patch maps4-add-proc-kpagecount-interface.patch maps4-add-proc-kpageflags-interface.patch maps4-make-page-monitoring-proc-file-optional.patch maps4-make-page-monitoring-proc-file-optional-fix.patch hugetlb-split-alloc_huge_page-into-private-and-shared-components.patch hugetlb-split-alloc_huge_page-into-private-and-shared-components-checkpatch-fixes.patch hugetlb-fix-quota-management-for-private-mappings.patch hugetlb-debit-quota-in-alloc_huge_page.patch hugetlb-allow-bulk-updating-in-hugetlb__quota.patch hugetlb-enforce-quotas-during-reservation-for-shared-mappings.patch add-remove_memory-for-ppc64-2.patch enable-hotplug-memory-remove-for-ppc64.patch add-arch-specific-walk_memory_remove-for-ppc64.patch r-o-bind-mounts-stub-functions.patch r-o-bind-mounts-elevate-write-count-opend-files.patch r-o-bind-mounts-elevate-write-count-for-some-ioctls.patch ext2-reservations-fix-for-r-o-bind-mounts-take-writer-count-v2.patch r-o-bind-mounts-elevate-writer-count-for-chown-and-friends.patch r-o-bind-mounts-make-access-use-mnt-check.patch r-o-bind-mounts-elevate-mnt-writers-for-callers-of-vfs_mkdir.patch r-o-bind-mounts-elevate-write-count-during-entire-ncp_ioctl.patch r-o-bind-mounts-elevate-write-count-during-entire-ncp_ioctl-fix.patch r-o-bind-mounts-elevate-write-count-for-link-and-symlink-calls.patch r-o-bind-mounts-elevate-mount-count-for-extended-attributes.patch r-o-bind-mounts-elevate-write-count-for-file_update_time.patch r-o-bind-mounts-unix_find_other-elevate-write-count-for-touch_atime.patch r-o-bind-mounts-unix_find_other-elevate-write-count-for-touch_atime-fix.patch r-o-bind-mounts-elevate-write-count-over-calls-to-vfs_rename.patch r-o-bind-mounts-nfs-check-mnt-instead-of-superblock-directly.patch r-o-bind-mounts-elevate-writer-count-for-do_sys_truncate.patch r-o-bind-mounts-elevate-write-count-for-do_utimes.patch r-o-bind-mounts-elevate-write-count-for-do_utimes-touch-command-causes-oops.patch r-o-bind-mounts-elevate-write-count-for-do_sys_utime-and-touch_atime.patch r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create.patch r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create-fix.patch r-o-bind-mounts-elevate-mnt-writers-for-vfs_unlink-callers.patch r-o-bind-mounts-do_rmdir-elevate-write-count.patch r-o-bind-mounts-track-number-of-mount-writers.patch r-o-bind-mounts-track-number-of-mount-writers-make-lockdep-happy-with-r-o-bind-mounts.patch r-o-bind-mounts-track-number-of-mount-writers-fix.patch r-o-bind-mounts-honor-r-w-changes-at-do_remount-time.patch reiser4.patch page-owner-tracking-leak-detector.patch - To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html