On Thu, Mar 29, 2018 at 9:26 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Thu, Mar 29, 2018 at 6:42 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
>> 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.
>
> And that would need to be the default if selected by a kernel config
> option. Should we do that now, to prevent surprises? Maybe we
> should; it does't cost anything in complexity, and I think it's better
> to let the user choose between backward compatibility and new feature.
>
So you mean same as other features?
OVERLAY_FS_XINO defaults to n
and mount options xino=on/off.
Makes sense.
I can do that.
Thanks,
Amir.
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