Re: REISERFS_MAX_NAME and ENAMETOOLONG

[Jeff Mahoney <jeffm@suse.com>]

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Vladimir V. Saveliev wrote:
> Hello
> 
> Xuân Baldauf wrote:
>>Hello,
>>
>>when downloading something from java.sun.com (e.g.
>>http://javashoplm.sun.com/ECom/docs/Welcome.jsp?StoreId=22&PartDetailId=jdk-1.5.0-doc-oth-JPR&SiteId=JSC&TransactionId=noreg
>>), very long URLs are encountered. When trying to download using "wget",
>>wget tries to open a file with those long filenames, and fails with
>>ENAMETOOLONG (File name too long).
>>
>>I think that the limit is due to the REISERFS_MAX_NAME macro
>>(http://lxr.linux.no/source/include/linux/reiserfs_fs.h?v=2.6.10#L1107),
>>which currently resolves to "255" (which supposedly means 255 bytes).
>>
>>Is it safe to change REISERFS_MAX_NAME to something larger, or does this
>>change the disk layout in an unexpected or incompatible way?
>>
> 
> Yes. Max long name in reiserfs used to be much longer and then it was changed for compilability with something.
> I believe you can easlily change it to 3500.

Just as a data point:

http://marc.theaimsgroup.com/?l=reiserfs&m=97908551206263&w=2

The current state:

The kernel doesn't care about the length of a file name, so long as the
maximum path used to access it is below PATH_MAX (currently 4k). dirents
are dynamically sized, so there is no more 255 byte limit inside the kernel.

Glibc still defines dirent->d_name as char[256] for backward
compatibility. If the kernel supports d_reclen (which it has for a very
long time), dirents are treated as dynamically sized. Since glibc
allocates an 8k (_IO_BUFSIZE) buffer and passes it to sys_getdents,
proper bounds checking is done, and the max length is supported.

I did a quick test using your suggestion on my development machine, and
got proper results back.

- -Jeff

- --
Jeff Mahoney
SuSE Labs
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