vfs: plumb i_version handling into struct kstat
The NFS server has a lot of special handling for different types of change attribute access, depending on the underlying filesystem. In most cases, it's doing a getattr anyway and then fetching that value after the fact. Rather that do that, add a new STATX_CHANGE_COOKIE flag that is a kernel-only symbol (for now). If requested and getattr can implement it, it can fill out this field. For IS_I_VERSION inodes, add a generic implementation in vfs_getattr_nosec. Take care to mask STATX_CHANGE_COOKIE off in requests from userland and in the result mask. Since not all filesystems can give the same guarantees of monotonicity, claim a STATX_ATTR_CHANGE_MONOTONIC flag that filesystems can set to indicate that they offer an i_version value that can never go backward. Eventually if we decide to make the i_version available to userland, we can just designate a field for it in struct statx, and move the STATX_CHANGE_COOKIE definition to the uapi header. Reviewed-by: NeilBrown <neilb@suse.de> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jeff Layton <jlayton@kernel.org>
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17
fs/stat.c
17
fs/stat.c
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@ -18,6 +18,7 @@
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#include <linux/syscalls.h>
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#include <linux/pagemap.h>
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#include <linux/compat.h>
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#include <linux/iversion.h>
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#include <linux/uaccess.h>
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#include <asm/unistd.h>
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@ -122,6 +123,11 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
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stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
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STATX_ATTR_DAX);
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if ((request_mask & STATX_CHANGE_COOKIE) && IS_I_VERSION(inode)) {
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stat->result_mask |= STATX_CHANGE_COOKIE;
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stat->change_cookie = inode_query_iversion(inode);
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}
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mnt_userns = mnt_user_ns(path->mnt);
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if (inode->i_op->getattr)
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return inode->i_op->getattr(mnt_userns, path, stat,
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@ -602,9 +608,11 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
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memset(&tmp, 0, sizeof(tmp));
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tmp.stx_mask = stat->result_mask;
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/* STATX_CHANGE_COOKIE is kernel-only for now */
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tmp.stx_mask = stat->result_mask & ~STATX_CHANGE_COOKIE;
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tmp.stx_blksize = stat->blksize;
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tmp.stx_attributes = stat->attributes;
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/* STATX_ATTR_CHANGE_MONOTONIC is kernel-only for now */
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tmp.stx_attributes = stat->attributes & ~STATX_ATTR_CHANGE_MONOTONIC;
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tmp.stx_nlink = stat->nlink;
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tmp.stx_uid = from_kuid_munged(current_user_ns(), stat->uid);
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tmp.stx_gid = from_kgid_munged(current_user_ns(), stat->gid);
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@ -643,6 +651,11 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags,
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if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
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return -EINVAL;
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/* STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests
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* from userland.
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*/
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mask &= ~STATX_CHANGE_COOKIE;
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error = vfs_statx(dfd, filename, flags, &stat, mask);
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if (error)
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return error;
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@ -52,6 +52,15 @@ struct kstat {
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u64 mnt_id;
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u32 dio_mem_align;
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u32 dio_offset_align;
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u64 change_cookie;
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};
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/* These definitions are internal to the kernel for now. Mainly used by nfsd. */
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/* mask values */
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#define STATX_CHANGE_COOKIE 0x40000000U /* Want/got stx_change_attr */
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/* file attribute values */
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#define STATX_ATTR_CHANGE_MONOTONIC 0x8000000000000000ULL /* version monotonically increases */
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#endif
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