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Go Back   Linux Archive > Redhat > Cluster Development

 
 
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Old 05-17-2010, 12:40 PM
Steven Whitehouse
 
Default GFS2: Fix writing to non-page aligned gfs2_quota structures

From: Abhijith Das <adas@redhat.com>

This is the upstream fix for this bug. This patch differs
from the RHEL5 fix (Red Hat bz #555754) which simply writes to the 8-byte
value field of the quota. In upstream quota code, we're
required to write the entire quota (88 bytes) which can be split
across a page boundary. We check for such quotas, and read/write
the two parts from/to the corresponding pages holding these parts.

With this patch, I don't see the bug anymore using the reproducer
in Red Hat bz 555754. I successfully ran a couple of simple tests/mounts/
umounts and it doesn't seem like this patch breaks anything else.

Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
---
fs/gfs2/quota.c | 86 +++++++++++++++++++++++++++++++++++++++----------------
1 files changed, 61 insertions(+), 25 deletions(-)

diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 6ca0967..d5f4661 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -637,15 +637,40 @@ static int gfs2_adjust_quota(struct gfs2_inode *ip, loff_t loc,
unsigned blocksize, iblock, pos;
struct buffer_head *bh, *dibh;
struct page *page;
- void *kaddr;
- struct gfs2_quota *qp;
- s64 value;
- int err = -EIO;
+ void *kaddr, *ptr;
+ struct gfs2_quota q, *qp;
+ int err, nbytes;
u64 size;

if (gfs2_is_stuffed(ip))
gfs2_unstuff_dinode(ip, NULL);
-
+
+ memset(&q, 0, sizeof(struct gfs2_quota));
+ err = gfs2_internal_read(ip, NULL, (char *)&q, &loc, sizeof(q));
+ if (err < 0)
+ return err;
+
+ err = -EIO;
+ qp = &q;
+ qp->qu_value = be64_to_cpu(qp->qu_value);
+ qp->qu_value += change;
+ qp->qu_value = cpu_to_be64(qp->qu_value);
+ qd->qd_qb.qb_value = qp->qu_value;
+ if (fdq) {
+ if (fdq->d_fieldmask & FS_DQ_BSOFT) {
+ qp->qu_warn = cpu_to_be64(fdq->d_blk_softlimit);
+ qd->qd_qb.qb_warn = qp->qu_warn;
+ }
+ if (fdq->d_fieldmask & FS_DQ_BHARD) {
+ qp->qu_limit = cpu_to_be64(fdq->d_blk_hardlimit);
+ qd->qd_qb.qb_limit = qp->qu_limit;
+ }
+ }
+
+ /* Write the quota into the quota file on disk */
+ ptr = qp;
+ nbytes = sizeof(struct gfs2_quota);
+get_a_page:
page = grab_cache_page(mapping, index);
if (!page)
return -ENOMEM;
@@ -667,7 +692,12 @@ static int gfs2_adjust_quota(struct gfs2_inode *ip, loff_t loc,
if (!buffer_mapped(bh)) {
gfs2_block_map(inode, iblock, bh, 1);
if (!buffer_mapped(bh))
- goto unlock;
+ goto unlock_out;
+ /* If it's a newly allocated disk block for quota, zero it */
+ if (buffer_new(bh)) {
+ memset(bh->b_data, 0, bh->b_size);
+ set_buffer_uptodate(bh);
+ }
}

if (PageUptodate(page))
@@ -677,32 +707,34 @@ static int gfs2_adjust_quota(struct gfs2_inode *ip, loff_t loc,
ll_rw_block(READ_META, 1, &bh);
wait_on_buffer(bh);
if (!buffer_uptodate(bh))
- goto unlock;
+ goto unlock_out;
}

gfs2_trans_add_bh(ip->i_gl, bh, 0);

kaddr = kmap_atomic(page, KM_USER0);
- qp = kaddr + offset;
- value = (s64)be64_to_cpu(qp->qu_value) + change;
- qp->qu_value = cpu_to_be64(value);
- qd->qd_qb.qb_value = qp->qu_value;
- if (fdq) {
- if (fdq->d_fieldmask & FS_DQ_BSOFT) {
- qp->qu_warn = cpu_to_be64(fdq->d_blk_softlimit);
- qd->qd_qb.qb_warn = qp->qu_warn;
- }
- if (fdq->d_fieldmask & FS_DQ_BHARD) {
- qp->qu_limit = cpu_to_be64(fdq->d_blk_hardlimit);
- qd->qd_qb.qb_limit = qp->qu_limit;
- }
- }
+ if (offset + sizeof(struct gfs2_quota) > PAGE_CACHE_SIZE)
+ nbytes = PAGE_CACHE_SIZE - offset;
+ memcpy(kaddr + offset, ptr, nbytes);
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
+ unlock_page(page);
+ page_cache_release(page);
+
+ /* If quota straddles page boundary, we need to update the rest of the
+ * quota at the beginning of the next page */
+ if (offset != 0) { /* first page, offset is closer to PAGE_CACHE_SIZE */
+ ptr = ptr + nbytes;
+ nbytes = sizeof(struct gfs2_quota) - nbytes;
+ offset = 0;
+ index++;
+ goto get_a_page;
+ }

+ /* Update the disk inode timestamp and size (if extended) */
err = gfs2_meta_inode_buffer(ip, &dibh);
if (err)
- goto unlock;
+ goto out;

size = loc + sizeof(struct gfs2_quota);
if (size > inode->i_size) {
@@ -715,7 +747,9 @@ static int gfs2_adjust_quota(struct gfs2_inode *ip, loff_t loc,
brelse(dibh);
mark_inode_dirty(inode);

-unlock:
+out:
+ return err;
+unlock_out:
unlock_page(page);
page_cache_release(page);
return err;
@@ -779,8 +813,10 @@ static int do_sync(unsigned int num_qd, struct gfs2_quota_data **qda)
* rgrp since it won't be allocated during the transaction
*/
al->al_requested = 1;
- /* +1 in the end for block requested above for unstuffing */
- blocks = num_qd * data_blocks + RES_DINODE + num_qd + 1;
+ /* +3 in the end for unstuffing block, inode size update block
+ * and another block in case quota straddles page boundary and
+ * two blocks need to be updated instead of 1 */
+ blocks = num_qd * data_blocks + RES_DINODE + num_qd + 3;

if (nalloc)
al->al_requested += nalloc * (data_blocks + ind_blocks);
--
1.6.2.5
 

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