[lustre-devel] [PATCH 18/30] lustre: llite: llite.stat_blocksize param for fixed st_blksize

[James Simmons <jsimmons@infradead.org>]

From: Andrew Perepechko <c17827@cray.com>

llite.stat_blocksize is added to allow configurable st_blksize
for stat(2). The latter is treated incorrectly by some
applications. For example, glibc pre-2.25 uses this value for
stdio buffering which completely ruins performance with random
reads.

The patch changes the behaviour of getattr rather than inode
initialization so that change of the setting causes immediate
effect without the need of reclaiming existing inodes.

The patch is similar to the patch from bz # 12739 by Aurelien
Degremont.

Signed-off-by: Andrew Perepechko <c17827@cray.com>
WC-bug-id: https://jira.whamcloud.com/browse/LU-9413
Reviewed-on: https://review.whamcloud.com/26869
Reviewed-by: Alexander Zarochentsev <c17826@cray.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 drivers/staging/lustre/lustre/llite/file.c         |  2 +-
 .../staging/lustre/lustre/llite/llite_internal.h   |  6 +++-
 drivers/staging/lustre/lustre/llite/lproc_llite.c  | 33 ++++++++++++++++++++++
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/file.c b/drivers/staging/lustre/lustre/llite/file.c
index b90c59c..94760eb 100644
--- a/drivers/staging/lustre/lustre/llite/file.c
+++ b/drivers/staging/lustre/lustre/llite/file.c
@@ -3267,7 +3267,7 @@ int ll_getattr(const struct path *path, struct kstat *stat,
 	stat->atime = inode->i_atime;
 	stat->mtime = inode->i_mtime;
 	stat->ctime = inode->i_ctime;
-	stat->blksize = 1 << inode->i_blkbits;
+	stat->blksize = sbi->ll_stat_blksize ?: BIT(inode->i_blkbits);
 
 	stat->nlink = inode->i_nlink;
 	stat->size = i_size_read(inode);
diff --git a/drivers/staging/lustre/lustre/llite/llite_internal.h b/drivers/staging/lustre/lustre/llite/llite_internal.h
index 9d9f623..dcb2fed 100644
--- a/drivers/staging/lustre/lustre/llite/llite_internal.h
+++ b/drivers/staging/lustre/lustre/llite/llite_internal.h
@@ -523,7 +523,11 @@ struct ll_sb_info {
 	struct root_squash_info	  ll_squash;
 	struct path		 ll_mnt;
 
-	__kernel_fsid_t		  ll_fsid;
+	/* st_blksize returned by stat(2), when non-zero */
+	unsigned int		 ll_stat_blksize;
+
+	__kernel_fsid_t		 ll_fsid;
+
 	struct kset		ll_kset;	/* sysfs object */
 	struct completion	 ll_kobj_unregister;
 };
diff --git a/drivers/staging/lustre/lustre/llite/lproc_llite.c b/drivers/staging/lustre/lustre/llite/lproc_llite.c
index f775b4f..d8ef090 100644
--- a/drivers/staging/lustre/lustre/llite/lproc_llite.c
+++ b/drivers/staging/lustre/lustre/llite/lproc_llite.c
@@ -128,6 +128,38 @@ static ssize_t blocksize_show(struct kobject *kobj, struct attribute *attr,
 }
 LUSTRE_RO_ATTR(blocksize);
 
+static ssize_t stat_blocksize_show(struct kobject *kobj, struct attribute *attr,
+				   char *buf)
+{
+	struct ll_sb_info *sbi = container_of(kobj, struct ll_sb_info,
+					      ll_kset.kobj);
+
+	return sprintf(buf, "%u\n", sbi->ll_stat_blksize);
+}
+
+static ssize_t stat_blocksize_store(struct kobject *kobj,
+				    struct attribute *attr,
+				    const char *buffer,
+				    size_t count)
+{
+	struct ll_sb_info *sbi = container_of(kobj, struct ll_sb_info,
+					      ll_kset.kobj);
+	unsigned int val;
+	int rc;
+
+	rc = kstrtouint(buffer, 10, &val);
+	if (rc)
+		return rc;
+
+	if (val != 0 && (val < PAGE_SIZE || (val & (val - 1))) != 0)
+		return -ERANGE;
+
+	sbi->ll_stat_blksize = val;
+
+	return count;
+}
+LUSTRE_RW_ATTR(stat_blocksize);
+
 static ssize_t kbytestotal_show(struct kobject *kobj, struct attribute *attr,
 				char *buf)
 {
@@ -1123,6 +1155,7 @@ static ssize_t ll_nosquash_nids_seq_write(struct file *file,
 
 static struct attribute *llite_attrs[] = {
 	&lustre_attr_blocksize.attr,
+	&lustre_attr_stat_blocksize.attr,
 	&lustre_attr_kbytestotal.attr,
 	&lustre_attr_kbytesfree.attr,
 	&lustre_attr_kbytesavail.attr,
-- 
1.8.3.1