Re: [PATCH 3/7] quota: add new quotactl Q_GETNEXTQUOTA
From: Jan Kara <jack@suse.cz>
Date: 2016-01-22 09:28:12
Also in:
linux-fsdevel, linux-xfs
On Thu 21-01-16 22:07:20, Eric Sandeen wrote:
Q_GETNEXTQUOTA is exactly like Q_GETQUOTA, except that it will return quota information for the id equal to or greater than the id requested. In other words, if the requested id has no quota, the command will return quota information for the next higher id which does have a quota set. If no higher id has an active quota, -ESRCH is returned. This allows filesystems to do efficient iteration in kernelspace, much like extN filesystems do in userspace when asked to report all active quotas. This does require a new data structure for userspace, as the current structure does not include an ID for the returned quota information. Today, Ext4 with a hidden quota inode requires getpwent-style iterations, and for systems which have i.e. LDAP backends, this can be very slow, or even impossible if iteration is not allowed in the configuration. Signed-off-by: Eric Sandeen <redacted>
Same comments as for XFS version apply here. Furthermore:
quoted hunk
diff --git a/fs/quota/compat.c b/fs/quota/compat.c index fb1892f..80773a4 100644 --- a/fs/quota/compat.c +++ b/fs/quota/compat.c@@ -19,6 +19,19 @@ struct compat_if_dqblk { compat_uint_t dqb_valid; }; +struct compat_if_nextdqblk { + compat_u64 dqb_bhardlimit; + compat_u64 dqb_bsoftlimit; + compat_u64 dqb_curspace; + compat_u64 dqb_ihardlimit; + compat_u64 dqb_isoftlimit; + compat_u64 dqb_curinodes; + compat_u64 dqb_btime; + compat_u64 dqb_itime; + compat_uint_t dqb_valid; + compat_uint_t dqb_id; +}; +
Is there a need for compat version of this structure? Everything is
naturally aligned and the size is a multiple of 8 bytes. But these things
keep surprising me... Added CC to linux-api in a hope that there's someone
who definitely knows.
On a side note when I have API people attention: AFAIU we need
struct compat_if_dqblk (defined in fs/quota/compat.c) because its size is
not multiple of 8 bytes, right? But what is then then reason for get_user()
/ put_user() when the structure is copied into userspace (see below)?
copy_in_user() should have copied everything...
if (copy_in_user(compat_dqblk, dqblk, sizeof(*compat_dqblk)) ||
get_user(data, &dqblk->dqb_valid) ||
put_user(data, &compat_dqblk->dqb_valid))
ret = -EFAULT;
Honza
--
Jan Kara [off-list ref]
SUSE Labs, CR
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