quota file question

[Dmitry Monakhov <dmonakhov@openvz.org>]

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I'm always wonder why do we have to allocate space for quota-file
as normal file. Because of this we have to grab i_mutex on each
quota write. And still getting in to risk of ENOSPC. The later is
really annoying issue for me(when i run fsstress tests).
Let's live the i_mutex's story for another day and consider the
simplest one. Why don't we preallocate a space for quota file
during creation. In fact we may imagine some reasonable quota-file
size expectation (65538 * 64) = 4Mb, At least this may be sufficient
for most use-cases.


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>From ef72d4ad7d23db734a7ce74b350cdd47a594130b Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Sun, 7 Mar 2010 20:08:51 +0300
Subject: [PATCH] quota: prealloc space for new quota file.


Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 convertquota.c |    4 ++--
 quotacheck.c   |    2 +-
 quotaio.c      |   15 ++++++++++++++-
 quotaio.h      |    2 +-
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/convertquota.c b/convertquota.c
index 1572cb9..2304be6 100644
--- a/convertquota.c
+++ b/convertquota.c
@@ -287,7 +287,7 @@ static int convert_format(int type, struct mntent *mnt)
 			type2name(type), mnt->mnt_dir);
 		return -1;
 	}
-	if (!(qn = new_io(mnt, type, QF_VFSV0))) {
+	if (!(qn = new_io(mnt, type, QF_VFSV0, 8192*1024))) {
 		errstr(_("Cannot create file for %ss for new format on %s: %s\n"),
 			type2name(type), mnt->mnt_dir, strerror(errno));
 		end_io(qo);
@@ -320,7 +320,7 @@ static int convert_endian(int type, struct mntent *mnt)
 		close(ofd);
 		return -1;
 	}
-	if (!(qn = new_io(mnt, type, QF_VFSV0))) {
+	if (!(qn = new_io(mnt, type, QF_VFSV0, 8192*1024))) {
 		errstr(_("Cannot create file for %ss for new format on %s: %s\n"),
 			type2name(type), mnt->mnt_dir, strerror(errno));
 		close(ofd);
diff --git a/quotacheck.c b/quotacheck.c
index b5f7e2e..2b49820 100644
--- a/quotacheck.c
+++ b/quotacheck.c
@@ -794,7 +794,7 @@ static int dump_to_file(struct mntent *mnt, int type)
 	struct quota_handle *h;
 
 	debug(FL_DEBUG, _("Dumping gathered data for %ss.\n"), type2name(type));
-	if (!(h = new_io(mnt, type, cfmt))) {
+	if (!(h = new_io(mnt, type, cfmt, 8192*1024))) {
 		errstr(_("Cannot initialize IO on new quotafile: %s\n"),
 			strerror(errno));
 		return -1;
diff --git a/quotaio.c b/quotaio.c
index d74a37d..540e89b 100644
--- a/quotaio.c
+++ b/quotaio.c
@@ -166,7 +166,7 @@ out_handle:
 /*
  *	Create new quotafile of specified format on given filesystem
  */
-struct quota_handle *new_io(struct mntent *mnt, int type, int fmt)
+struct quota_handle *new_io(struct mntent *mnt, int type, int fmt, int prealloc)
 {
 	char *qfname;
 	int fd;
@@ -212,6 +212,19 @@ struct quota_handle *new_io(struct mntent *mnt, int type, int fmt)
 		free(h);
 		goto out_fd;
 	}
+	if (prealloc) {
+		char zbuf[4096];
+		int len, ret;
+		memset(zbuf, 0, sizeof(zbuf));
+		while (prealloc) {
+			len = (sizeof(zbuf) < prealloc) ? sizeof(zbuf) : prealloc;
+			ret = write(fd, zbuf, len);
+			if (ret < 0)
+				goto out_fd;
+			prealloc -= len;
+		}
+		lseek(fd, 0, SEEK_SET);
+	}
 	return h;
       out_fd:
 	close(fd);
diff --git a/quotaio.h b/quotaio.h
index f6eef50..c66db43 100644
--- a/quotaio.h
+++ b/quotaio.h
@@ -169,7 +169,7 @@ static inline void mark_quotafile_info_dirty(struct quota_handle *h)
 struct quota_handle *init_io(struct mntent *mnt, int type, int fmt, int flags);
 
 /* Create new quotafile of specified format on given filesystem */
-struct quota_handle *new_io(struct mntent *mnt, int type, int fmt);
+struct quota_handle *new_io(struct mntent *mnt, int type, int fmt, int prealloc);
 
 /* Close quotafile */
 int end_io(struct quota_handle *h);
-- 
1.6.3.3