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Re: [PATCH] mkfs.xfs: fix protofile name create block reservation

To: Eric Sandeen <sandeen@xxxxxxxxxx>
Subject: Re: [PATCH] mkfs.xfs: fix protofile name create block reservation
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Wed, 07 Aug 2013 15:19:17 -0500
Cc: Boris Ranto <branto@xxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <5201E28B.1050800@xxxxxxxxxx>
References: <5201E28B.1050800@xxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0
On 08/07/13 01:00, Eric Sandeen wrote:
A large protofile which creates a large directory and requires
a a dir tree split, can fail:

   mkfs.xfs: directory createname error [28 - No space left on device]

This is because when we've split a block once, we decrement args->total:
(see kernel commit a7444053fb3ebd3d905e3c7a7bd5ea80a54b083a for the
rationale)

        /* account for newly allocated blocks in reserved blocks total */
        args->total -= dp->i_d.di_nblocks - nblks;

but every call into this path from proto file parsing started
reserved / args->total as only "1" as passed tro newdirent() -
so if we allocate a block, args->total hits 0, and then in
xfs_dir2_node_addname():

         /*
          * Add the new leaf entry.
          */
         rval = xfs_dir2_leafn_add(blk->bp, args, blk->index);
         if (rval == 0) {
                ...
         } else {
                 /*
                  * It didn't work, we need to split the leaf block.
                  */
                 if (args->total == 0) {
                         ASSERT(rval == ENOSPC);
                         goto done;
                 }
                 /*
                  * Split the leaf block and insert the new entry.
                  */

we hit the args->total == 0 special case, and don't do the next
split, and ENOSPC gets returned all the way up, and we fail.

So rather than calling newdirent with a total of "1" in every case,
which doesn't account for possible tree splits, we should call it
with a more appropriate value: XFS_DIRENTER_SPACE_RES(mp, name->len),
which will handle the maximum nr of block allocations that might be
needed during a directory entry insert.

Since the reservation required doesn't depend on entry type,
just push this down a level, into newdirent() itself.

Reported-by: Boris Ranto<branto@xxxxxxxxxx>
Signed-off-by: Eric Sandeen<sandeen@xxxxxxxxxx>
---

Looks good. This does not harm the current version of the Linux 3.12 crc xfsprogs series at all. But we will wait for the weekly community phone call before any new commits.

Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>

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