Ceph » CephFS

When the layout fields of a file are modified using setfattr, this file must be empty, otherwise an error will occur.

how to explain this ,why the file must be empty?

How to remove this restriction

I already know the mistake，the file I set has non-zero size,But i also want to set the non-zero size file.I want to delete the code below:

if (cur->get_projected_inode()->size ||
cur->get_projected_inode()->truncate_seq > 1) {
respond_to_request(mdr, -ENOTEMPTY);
return;
}

in Server.cc->handle_set_vxattr

I wonder if this will cause other mistakes.

yuanli zhu wrote:

I already know the mistake，the file I set has non-zero size,But i also want to set the non-zero size file.I want to delete the code below:

if (cur->get_projected_inode()->size ||
cur->get_projected_inode()->truncate_seq > 1) {
respond_to_request(mdr, -ENOTEMPTY);
return;
}

in Server.cc->handle_set_vxattr

I wonder if this will cause other mistakes.

It will. Changing the layout will confuse the client and cause it to write to the file's data stripes differently from the previous layout. File data may be clobbered, turned to gibberish, etc.

Migrating a file to a different layout is an idea that's come up periodically but an efficient and understandable mechanism for doing so is unsettled.

Patrick Donnelly wrote:

yuanli zhu wrote:

I already know the mistake，the file I set has non-zero size,But i also want to set the non-zero size file.I want to delete the code below:

if (cur->get_projected_inode()->size ||
cur->get_projected_inode()->truncate_seq > 1) {
respond_to_request(mdr, -ENOTEMPTY);
return;
}

in Server.cc->handle_set_vxattr

I wonder if this will cause other mistakes.

It will. Changing the layout will confuse the client and cause it to write to the file's data stripes differently from the previous layout. File data may be clobbered, turned to gibberish, etc.

Migrating a file to a different layout is an idea that's come up periodically but an efficient and understandable mechanism for doing so is unsettled.

I want add one attr to ceph.file.layout.like ceph.file.layout.protect.I can add to file_layout_t success,but i can not modify it.

struct file_layout_t {
// file -> object mapping
uint32_t stripe_unit; ///< stripe unit, in bytes,
uint32_t stripe_count; ///< over this many objects
uint32_t object_size; ///< until objects are this big
uint32_t protect; //modify by zyli

int64_t pool_id;        ///< rados pool id
  string pool_ns;         ///< rados pool namespace

file_layout_t(uint32_t su=0, uint32_t sc=0, uint32_t os=0,uint32_t pro=0)
    : stripe_unit(su),
      stripe_count(sc),
      object_size(os),
      protect(pro),
      pool_id(-1) {
  }

in fs_types.h

1. file: nas/cephfs/zyli.txt
   ceph.file.layout.protect="0"

1. file: nas/cephfs/zyli.txt
   ceph.file.layout.protect="0"

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