On Thu, Mar 29, 2018 at 6:58 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Thu, Mar 29, 2018 at 4:18 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
>> On 64bit systems, when overlay layers are not all on the same fs, but
>> all inode numbers of underlying fs are not using the high bits, use the
>> high bits to partition the overlay st_ino address space. The high bits
>> hold the fsid (upper fsid is 0). This way overlay inode numbers are unique
>> and all inodes use overlay st_dev. Inode numbers are also persistent
>> for a given layer configuration.
>>
>> Currently, our only indication for available high ino bits is from a
>> filesystem that supports file handles and uses the default encode_fh()
>> operation, which encodes a 32bit inode number.
>>
>> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
>> ---
>> fs/overlayfs/inode.c | 31 +++++++++++++++++++++++++++++--
>> fs/overlayfs/overlayfs.h | 3 ++-
>> fs/overlayfs/ovl_entry.h | 2 ++
>> fs/overlayfs/super.c | 26 ++++++++++++++++++++++----
>> fs/overlayfs/util.c | 24 +++++++++++++++++++++---
>> 5 files changed, 76 insertions(+), 10 deletions(-)
>>
>> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
>> index 89dfab20fe0e..7fc9c83bf2ff 100644
>> --- a/fs/overlayfs/inode.c
>> +++ b/fs/overlayfs/inode.c
>> @@ -63,6 +63,7 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat)
>> {
>> struct ovl_layer *lower_layer = ovl_layer_lower(dentry);
>> bool samefs = ovl_same_sb(dentry->d_sb);
>> + int xinobits = ovl_xino_bits(dentry->d_sb);
>>
>> if (samefs) {
>> /*
>> @@ -71,7 +72,31 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat)
>> * which is friendly to du -x.
>> */
>> stat->dev = dentry->d_sb->s_dev;
>> - } else if (S_ISDIR(dentry->d_inode->i_mode)) {
>> + return 0;
>> + } else if (xinobits) {
>> + /*
>> + * All inode numbers of underlying fs should not be using the
>> + * high xinobits, so we use high xinobits to partition the
>> + * overlay st_ino address space. The high bits holds the fsid
>> + * (upper fsid is 0). This way overlay inode numbers are unique
>> + * and all inodes use overlay st_dev. Inode numbers are also
>> + * persistent for a given layer configuration.
>> + */
>> + if (stat->ino >> (64 - xinobits)) {
>> + pr_warn_ratelimited("overlayfs: inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
>> + dentry, stat->ino, xinobits);
>> + } else {
>> + if (lower_layer) {
>> + stat->ino |= ((u64)lower_layer->fsid)
>> + << (64 - xinobits);
>> + }
>> + stat->dev = dentry->d_sb->s_dev;
>> + return 0;
>> + }
>> + }
>> +
>> + /* The inode could not be mapped to a unified st_ino address space */
>> + if (S_ISDIR(dentry->d_inode->i_mode)) {
>> /*
>> * Always use the overlay st_dev for directories, so 'find
>> * -xdev' will scan the entire overlay mount and won't cross the
>> @@ -117,11 +142,13 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
>> /*
>> * For non-dir or same fs, we use st_ino of the copy up origin.
>> * This guaranties constant st_dev/st_ino across copy up.
>> + * With xino feature and non-samefs, we use st_ino of the copy up
>> + * origin masked with high bits that represent the layer id.
>> *
>> * If lower filesystem supports NFS file handles, this also guaranties
>> * persistent st_ino across mount cycle.
>> */
>> - if (!is_dir || samefs) {
>> + if (!is_dir || samefs || ovl_xino_bits(dentry->d_sb)) {
>> if (OVL_TYPE_ORIGIN(type)) {
>> struct kstat lowerstat;
>> u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0);
>> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
>> index 4432599ecbc6..09f5b8ce70aa 100644
>> --- a/fs/overlayfs/overlayfs.h
>> +++ b/fs/overlayfs/overlayfs.h
>> @@ -202,7 +202,8 @@ void ovl_drop_write(struct dentry *dentry);
>> struct dentry *ovl_workdir(struct dentry *dentry);
>> const struct cred *ovl_override_creds(struct super_block *sb);
>> struct super_block *ovl_same_sb(struct super_block *sb);
>> -bool ovl_can_decode_fh(struct super_block *sb);
>> +int ovl_xino_bits(struct super_block *sb);
>> +int ovl_can_decode_fh(struct super_block *sb);
>> struct dentry *ovl_indexdir(struct super_block *sb);
>> bool ovl_index_all(struct super_block *sb);
>> bool ovl_verify_lower(struct super_block *sb);
>> diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
>> index e1c838c27a74..6a077fb2a75f 100644
>> --- a/fs/overlayfs/ovl_entry.h
>> +++ b/fs/overlayfs/ovl_entry.h
>> @@ -63,6 +63,8 @@ struct ovl_fs {
>> /* Did we take the inuse lock? */
>> bool upperdir_locked;
>> bool workdir_locked;
>> + /* Inode numbers in all layers do not use the high xino_bits */
>> + int xino_bits;
>> };
>>
>> /* private information held for every overlayfs dentry */
>> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
>> index 7d97d30cad39..d7284444f404 100644
>> --- a/fs/overlayfs/super.c
>> +++ b/fs/overlayfs/super.c
>> @@ -17,6 +17,7 @@
>> #include <linux/statfs.h>
>> #include <linux/seq_file.h>
>> #include <linux/posix_acl_xattr.h>
>> +#include <linux/exportfs.h>
>> #include "overlayfs.h"
>>
>> MODULE_AUTHOR("Miklos Szeredi <miklos@xxxxxxxxxx>");
>> @@ -701,6 +702,7 @@ static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
>> static int ovl_lower_dir(const char *name, struct path *path,
>> struct ovl_fs *ofs, int *stack_depth, bool *remote)
>> {
>> + int fh_type;
>> int err;
>>
>> err = ovl_mount_dir_noesc(name, path);
>> @@ -720,15 +722,19 @@ static int ovl_lower_dir(const char *name, struct path *path,
>> * The inodes index feature and NFS export need to encode and decode
>> * file handles, so they require that all layers support them.
>> */
>> + fh_type = ovl_can_decode_fh(path->dentry->d_sb);
>> if ((ofs->config.nfs_export ||
>> - (ofs->config.index && ofs->config.upperdir)) &&
>> - !ovl_can_decode_fh(path->dentry->d_sb)) {
>> + (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
>> ofs->config.index = false;
>> ofs->config.nfs_export = false;
>> pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
>> name);
>> }
>>
>> + /* Check if lower fs has 32bit inode numbers */
>> + if (fh_type != FILEID_INO32_GEN)
>> + ofs->xino_bits = 0;
>> +
>> return 0;
>>
>> out_put:
>> @@ -952,6 +958,7 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
>> {
>> struct vfsmount *mnt = ofs->upper_mnt;
>> struct dentry *temp;
>> + int fh_type;
>> int err;
>>
>> err = mnt_want_write(mnt);
>> @@ -1001,12 +1008,16 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
>> }
>>
>> /* Check if upper/work fs supports file handles */
>> - if (ofs->config.index &&
>> - !ovl_can_decode_fh(ofs->workdir->d_sb)) {
>> + fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
>> + if (ofs->config.index && !fh_type) {
>> ofs->config.index = false;
>> pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
>> }
>>
>> + /* Check if upper fs has 32bit inode numbers */
>> + if (fh_type != FILEID_INO32_GEN)
>> + ofs->xino_bits = 0;
>> +
>> /* NFS export of r/w mount depends on index */
>> if (ofs->config.nfs_export && !ofs->config.index) {
>> pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
>> @@ -1185,6 +1196,11 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
>> }
>> ofs->numlower++;
>> }
>> +
>> + /* When all layers on same fs, overlay can use real inode numbers */
>> + if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt))
>> + ofs->xino_bits = 0;
>> +
>> err = 0;
>> out:
>> return err;
>> @@ -1308,6 +1324,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
>>
>> sb->s_stack_depth = 0;
>> sb->s_maxbytes = MAX_LFS_FILESIZE;
>> + /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
>> + ofs->xino_bits = BITS_PER_LONG - 32;
>
> This disables xino for 32bit archs. Which is probably the right thing
> to do, otherwise there might be a regression in some cases since
> kernel will return EOVERFLOW if st_ino would overflow. Well, this is
> true for 32bit mode in 64bit kernel as well, so the above is not a
> perfect solution.
>
> Not sure if we need to worry. For 32bit archs, I think disabling xino
> is OK; it can be enabled explicitly if needed. For 64bit archs, let's
> hope it doesn't regress for anybody and if it does, we need to take
> steps.
Perhaps, the steps would be to implement -o noxino.
>
> So if you agree, I'll just add these as a comment.
>
Ok.
Thanks,
Amir.
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