Hmm. I think because users can append to any file at any time, and also append to a file then write to it normally, we might override the users preferred layout for a file where appending is just a small part of the plan. (And of course since we can’t control when users do append, it doesn’t let us handle the locking differently.) ________________________________ From: lustre-discuss <lustre-discuss-boun...@lists.lustre.org> on behalf of Degremont, Aurelien <degre...@amazon.com> Sent: Friday, March 29, 2019 4:53:42 AM To: Andreas Dilger; LEIBOVICI Thomas Cc: lustre-discuss@lists.lustre.org Subject: Re: [lustre-discuss] EINVAL error when writing to a PFL file (lustre 2.12.0)
Another thought I just had while re-reading LU-9341 is whether it would be better to have the MDS always create files opened with O_APPEND with stripe_count=1? There is no write parallelism for O_APPEND files, so having multiple stripes doesn't help the writer. Because the writer also always locks the whole file [0,EOF] then there is no read-write parallelism either, so creating only a single file stripe simplifies things significantly with no real loss. Having several stripes if still useful if you want to distribute space usage among several OSTs and also it could help if you have multiple readers later for this file. Aurélien Cheers, Andreas On Feb 22, 2019, at 10:09, LEIBOVICI Thomas <thomas.leibov...@cea.fr> wrote: > > Hello Patrick, > > Thank you for the quick reply. > No, I have no particular use-case in mind, I'm just playing around with PFL. > > If this is currently not properly supported, a quick fix could be to prevent the user from creating such incomplete layouts? > > Regards, > Thomas > > On 2/22/19 5:33 PM, Patrick Farrell wrote: >> Thomas, >> >> This is expected, but it's also something we'd like to fix - See LU-9341. >> >> Basically, append tries to instantiate the layout from 0 to infinity, and it fails because your layout is incomplete (ie doesn't go to infinity). >> >> May I ask why you're creating a file with an incomplete layout? Do you have a use case in mind? >> >> - Patrick >> From: lustre-discuss <lustre-discuss-boun...@lists.lustre.org> on behalf of LEIBOVICI Thomas <thomas.leibov...@cea.fr> >> Sent: Friday, February 22, 2019 10:27:48 AM >> To: lustre-discuss@lists.lustre.org >> Subject: [lustre-discuss] EINVAL error when writing to a PFL file (lustre 2.12.0) >> >> Hello, >> >> Is it expected to get an error when appending a PFL file made of 2 >> regions [0 - 1M] and [1M to 6M] >> even if writing in this range? >> >> I get an error when appending it, even when writting in the very first >> bytes: >> >> [root@vm0]# lfs setstripe -E 1M -c 1 -E 6M -c 2 /mnt/lustre/m_fou3 >> >> [root@vm0]# lfs getstripe /mnt/lustre/m_fou3 >> /mnt/lustre/m_fou3 >> lcm_layout_gen: 2 >> lcm_mirror_count: 1 >> lcm_entry_count: 2 >> lcme_id: 1 >> lcme_mirror_id: 0 >> lcme_flags: init >> lcme_extent.e_start: 0 >> lcme_extent.e_end: 1048576 >> lmm_stripe_count: 1 >> lmm_stripe_size: 1048576 >> lmm_pattern: raid0 >> lmm_layout_gen: 0 >> lmm_stripe_offset: 3 >> lmm_objects: >> - 0: { l_ost_idx: 3, l_fid: [0x100030000:0x9cf:0x0] } >> >> lcme_id: 2 >> lcme_mirror_id: 0 >> lcme_flags: 0 >> lcme_extent.e_start: 1048576 >> lcme_extent.e_end: 6291456 >> lmm_stripe_count: 2 >> lmm_stripe_size: 1048576 >> lmm_pattern: raid0 >> lmm_layout_gen: 0 >> lmm_stripe_offset: -1 >> >> [root@vm0]# stat -c %s /mnt/lustre/m_fou3 >> 14 >> >> * append fails: >> >> [root@vm0]# echo qsdkjqslkdjkj >> /mnt/lustre/m_fou3 >> bash: echo: write error: Invalid argument >> >> # strace indicates that write() gets the error: >> >> write(1, "qsdkjqslkdjkj\n", 14) = -1 EINVAL (Invalid argument) >> >> * no error in case of an open/truncate: >> >> [root@vm0]# echo qsdkjqslkdjkj > /mnt/lustre/m_fou3 >> >> OK >> >> Is it expected or should I open a ticket? >> >> Thomas >> >> _______________________________________________ >> lustre-discuss mailing list >> lustre-discuss@lists.lustre.org >> http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org > > _______________________________________________ > lustre-discuss mailing list > lustre-discuss@lists.lustre.org > http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org Cheers, Andreas --- Andreas Dilger CTO Whamcloud _______________________________________________ lustre-discuss mailing list lustre-discuss@lists.lustre.org http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org _______________________________________________ lustre-discuss mailing list lustre-discuss@lists.lustre.org http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
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