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Support for longnames for files/directories (Linux part)

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This patch adds the ability for zfs to support file/dir name up to 1023
bytes. This number is chosen so we can support up to 255 4-byte
characters. This new feature is represented by the new feature flag
feature@longname.

A new dataset property "longname" is also introduced to toggle longname
support for each dataset individually. This property can be disabled,
even if it contains longname files. In such case, new file cannot be
created with longname but existing longname files can still be looked
up.

Note that, to my knowledge native Linux filesystems don't support name
longer than 255 bytes. So there might be programs not able to work with
longname.

Note that NFS server may needs to use exportfs_get_name to reconnect
dentries, and the buffer being passed is limit to NAME_MAX+1 (256). So
NFS may not work when longname is enabled.

Note, FreeBSD vfs layer imposes a limit of 255 name lengh, so even
though we add code to support it here, it won't actually work.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
Closes #15921
This commit is contained in:
Sanjeev Bagewadi
2021-06-18 08:55:01 +00:00
committed by Brian Behlendorf
parent 3cf2bfa570
commit 20232ecfaa
41 changed files with 1239 additions and 406 deletions
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module/os/linux/zfs/zfs_vnops_os.c
+41 -1
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@@ -542,6 +542,46 @@ zfs_lookup(znode_t *zdp, char *nm, znode_t **zpp, int flags, cred_t *cr,
return (error);
}
/*
* Perform a linear search in directory for the name of specific inode.
* Note we don't pass in the buffer size of name because it's hardcoded to
* NAME_MAX+1(256) in Linux.
*
* IN: dzp - znode of directory to search.
* zp - znode of the target
*
* OUT: name - dentry name of the target
*
* RETURN: 0 on success, error code on failure.
*/
int
zfs_get_name(znode_t *dzp, char *name, znode_t *zp)
{
zfsvfs_t *zfsvfs = ZTOZSB(dzp);
int error = 0;
if ((error = zfs_enter_verify_zp(zfsvfs, dzp, FTAG)) != 0)
return (error);
if ((error = zfs_verify_zp(zp)) != 0) {
zfs_exit(zfsvfs, FTAG);
return (error);
}
/* ctldir should have got their name in zfs_vget */
if (dzp->z_is_ctldir || zp->z_is_ctldir) {
zfs_exit(zfsvfs, FTAG);
return (ENOENT);
}
/* buffer len is hardcoded to 256 in Linux kernel */
error = zap_value_search(zfsvfs->z_os, dzp->z_id, zp->z_id,
ZFS_DIRENT_OBJ(-1ULL), name, ZAP_MAXNAMELEN);
zfs_exit(zfsvfs, FTAG);
return (error);
}
/*
* Attempt to create a new entry in a directory. If the entry
* already exists, truncate the file if permissible, else return
@@ -1548,7 +1588,7 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
os = zfsvfs->z_os;
offset = ctx->pos;
prefetch = zp->z_zn_prefetch;
zap = zap_attribute_alloc();
zap = zap_attribute_long_alloc();
/*
* Initialize the iterator cursor.