Hi Yan,
On Sat, 3 Nov 2012, Yan, Zheng wrote:
> From: "Yan, Zheng" <zheng.z.yan@xxxxxxxxx>
>
> ceph_aio_write() has an optimization that marks cap EPH_CAP_FILE_WR
> dirty before data is copied to page cache and inode size is updated.
> If sceph_check_caps() flushes the dirty cap before the inode size is
> updated, MDS can miss the new inode size. The fix is move
> ceph_{get,put}_cap_refs() into ceph_write_{begin,end}() and call
> __ceph_mark_dirty_caps() after inode size is updated.
>
> Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
Hmm, I'm a little worried at the get/put caps sequence inside of
write_begin/end since that happens on every page... do you think it's
something to worry about?
The Fw revocation kludge was something we hit in practice. It looks like
balance_dirty_pages*() happens outside of the write_begin/_end calls in
generic_perform_write(), so that's a win.
Comments below:
> ---
> Changes since v1
> - Fix a cap leak when ceph_write_begin fail to get page
>
> fs/ceph/addr.c | 51 +++++++++++++++++++++++++++++++++++++++----
> fs/ceph/file.c | 69 +++++++++++++++++++++++-----------------------------------
> 2 files changed, 74 insertions(+), 46 deletions(-)
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 22b6e45..21a0718 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -1078,23 +1078,51 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
> struct page **pagep, void **fsdata)
> {
> struct inode *inode = file->f_dentry->d_inode;
> + struct ceph_inode_info *ci = ceph_inode(inode);
> + struct ceph_file_info *fi = file->private_data;
> struct page *page;
> pgoff_t index = pos >> PAGE_CACHE_SHIFT;
> - int r;
> + int r, want, got = 0;
> +
> + if (fi->fmode & CEPH_FILE_MODE_LAZY)
> + want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
> + else
> + want = CEPH_CAP_FILE_BUFFER;
> +
> + dout("write_begin %p %llx.%llx %llu~%u getting caps. i_size %llu\n",
> + inode, ceph_vinop(inode), pos, len, inode->i_size);
> + r = ceph_get_caps(ci, CEPH_CAP_FILE_WR, want, &got, pos+len);
> + if (r < 0)
> + return r;
> + dout("write_begin %p %llx.%llx %llu~%u got cap refs on %s\n",
> + inode, ceph_vinop(inode), pos, len, ceph_cap_string(got));
> + if (!(got & (CEPH_CAP_FILE_BUFFER|CEPH_CAP_FILE_LAZYIO))) {
> + ceph_put_cap_refs(ci, got);
> + return -EAGAIN;
> + }
>
> do {
> /* get a page */
> page = grab_cache_page_write_begin(mapping, index, 0);
> - if (!page)
> - return -ENOMEM;
> - *pagep = page;
> + if (!page) {
> + r = -ENOMEM;
> + break;
> + }
>
> dout("write_begin file %p inode %p page %p %d~%d\n", file,
> inode, page, (int)pos, (int)len);
>
> r = ceph_update_writeable_page(file, pos, len, page);
> + if (r)
> + page_cache_release(page);
> } while (r == -EAGAIN);
>
> + if (r) {
> + ceph_put_cap_refs(ci, got);
> + } else {
> + *pagep = page;
> + *(int *)fsdata = got;
> + }
> return r;
> }
>
> @@ -1108,10 +1136,12 @@ static int ceph_write_end(struct file *file, struct address_space *mapping,
> struct page *page, void *fsdata)
> {
> struct inode *inode = file->f_dentry->d_inode;
> + struct ceph_inode_info *ci = ceph_inode(inode);
> struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
> struct ceph_mds_client *mdsc = fsc->mdsc;
> unsigned from = pos & (PAGE_CACHE_SIZE - 1);
> int check_cap = 0;
> + int got = (unsigned long)fsdata;
>
> dout("write_end file %p inode %p page %p %d~%d (%d)\n", file,
> inode, page, (int)pos, (int)copied, (int)len);
> @@ -1134,6 +1164,19 @@ static int ceph_write_end(struct file *file, struct address_space *mapping,
> up_read(&mdsc->snap_rwsem);
> page_cache_release(page);
>
> + if (copied > 0) {
> + int dirty;
> + spin_lock(&ci->i_ceph_lock);
> + dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR);
> + spin_unlock(&ci->i_ceph_lock);
> + if (dirty)
> + __mark_inode_dirty(inode, dirty);
> + }
> +
> + dout("write_end %p %llx.%llx %llu~%u dropping cap refs on %s\n",
> + inode, ceph_vinop(inode), pos, len, ceph_cap_string(got));
> + ceph_put_cap_refs(ci, got);
> +
> if (check_cap)
> ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY, NULL);
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 5840d2a..266f6e0 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -712,63 +712,49 @@ static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov,
> struct ceph_osd_client *osdc =
> &ceph_sb_to_client(inode->i_sb)->client->osdc;
> loff_t endoff = pos + iov->iov_len;
> - int want, got = 0;
> - int ret, err;
> + int got = 0;
> + int ret, err, written;
>
> if (ceph_snap(inode) != CEPH_NOSNAP)
> return -EROFS;
>
> retry_snap:
> + written = 0;
> if (ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_FULL))
> return -ENOSPC;
> __ceph_do_pending_vmtruncate(inode);
> - dout("aio_write %p %llx.%llx %llu~%u getting caps. i_size %llu\n",
> - inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
> - inode->i_size);
> - if (fi->fmode & CEPH_FILE_MODE_LAZY)
> - want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
> - else
> - want = CEPH_CAP_FILE_BUFFER;
> - ret = ceph_get_caps(ci, CEPH_CAP_FILE_WR, want, &got, endoff);
> - if (ret < 0)
> - goto out_put;
> -
> - dout("aio_write %p %llx.%llx %llu~%u got cap refs on %s\n",
> - inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
> - ceph_cap_string(got));
> -
> - if ((got & (CEPH_CAP_FILE_BUFFER|CEPH_CAP_FILE_LAZYIO)) == 0 ||
This check seems to have been dropped... I think we want
> - (iocb->ki_filp->f_flags & O_DIRECT) ||
> - (inode->i_sb->s_flags & MS_SYNCHRONOUS) ||
> - (fi->flags & CEPH_F_SYNC)) {
> - ret = ceph_sync_write(file, iov->iov_base, iov->iov_len,
> - &iocb->ki_pos);
> - } else {
> - /*
> - * buffered write; drop Fw early to avoid slow
> - * revocation if we get stuck on balance_dirty_pages
> - */
> - int dirty;
> -
> - spin_lock(&ci->i_ceph_lock);
> - dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR);
> - spin_unlock(&ci->i_ceph_lock);
> - ceph_put_cap_refs(ci, got);
>
> + if (!(iocb->ki_filp->f_flags & O_DIRECT) &&
> + !(inode->i_sb->s_flags & MS_SYNCHRONOUS) &&
> + !(fi->flags & CEPH_F_SYNC)) {
> ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
> + if (ret >= 0)
> + written = ret;
> +
> if ((ret >= 0 || ret == -EIOCBQUEUED) &&
> ((file->f_flags & O_SYNC) || IS_SYNC(file->f_mapping->host)
> || ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL))) {
> - err = vfs_fsync_range(file, pos, pos + ret - 1, 1);
> + err = vfs_fsync_range(file, pos, pos + written - 1, 1);
> if (err < 0)
> ret = err;
> }
> -
> - if (dirty)
> - __mark_inode_dirty(inode, dirty);
> - goto out;
> + if ((ret < 0 && ret != -EAGAIN) || pos + written >= endoff)
> + goto out;
This check makes me nervous. The *only* time we want to jump to the sync
path is when we get -EAGAIN, right? I'd rather see that branch explicitly
taken immediately after generic_file_aio_write(). I'm not sure when we'd
do a short write in generic_file_aio_write(), but I'm pretty sure we don't
want to fall back to a sync write in that case...
> }
>
> + dout("aio_write %p %llx.%llx %llu~%u getting caps. i_size %llu\n",
> + inode, ceph_vinop(inode), pos + written,
> + (unsigned)iov->iov_len - written, inode->i_size);
> + ret = ceph_get_caps(ci, CEPH_CAP_FILE_WR, 0, &got, endoff);
> + if (ret < 0)
> + goto out_put;
We don't want to put if the get failed.
An incremental patch is below.
> +
> + dout("aio_write %p %llx.%llx %llu~%u got cap refs on %s\n",
> + inode, ceph_vinop(inode), pos + written,
> + (unsigned)iov->iov_len - written, ceph_cap_string(got));
> +
> + ret = ceph_sync_write(file, iov->iov_base + written,
> + iov->iov_len - written, &iocb->ki_pos);
> if (ret >= 0) {
> int dirty;
> spin_lock(&ci->i_ceph_lock);
> @@ -780,10 +766,9 @@ retry_snap:
>
> out_put:
> dout("aio_write %p %llx.%llx %llu~%u dropping cap refs on %s\n",
> - inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
> - ceph_cap_string(got));
> + inode, ceph_vinop(inode), pos + written,
> + (unsigned)iov->iov_len - written, ceph_cap_string(got));
> ceph_put_cap_refs(ci, got);
> -
> out:
> if (ret == -EOLDSNAPC) {
> dout("aio_write %p %llx.%llx %llu~%u got EOLDSNAPC, retrying\n",
> --
> 1.7.11.7
How does the below look to you?
There are a few test programs in ceph.git/qa/workunits/direct_io that try
to verify the O_DIRECT and sync io paths work. Have you tested those?
I'll queue this up on our qa cluster shortly.
Thanks!
sage
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 266f6e0..2a94102 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -724,10 +724,16 @@ retry_snap:
return -ENOSPC;
__ceph_do_pending_vmtruncate(inode);
+ /*
+ * try to do a buffered write. if we don't have sufficient
+ * caps, we'll get -EAGAIN from generic_file_aio_write.
+ */
if (!(iocb->ki_filp->f_flags & O_DIRECT) &&
!(inode->i_sb->s_flags & MS_SYNCHRONOUS) &&
!(fi->flags & CEPH_F_SYNC)) {
ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
+ if (ret == -EAGAIN)
+ goto sync_write;
if (ret >= 0)
written = ret;
@@ -738,16 +744,16 @@ retry_snap:
if (err < 0)
ret = err;
}
- if ((ret < 0 && ret != -EAGAIN) || pos + written >= endoff)
- goto out;
+ goto out;
}
+sync_write:
dout("aio_write %p %llx.%llx %llu~%u getting caps. i_size %llu\n",
inode, ceph_vinop(inode), pos + written,
(unsigned)iov->iov_len - written, inode->i_size);
ret = ceph_get_caps(ci, CEPH_CAP_FILE_WR, 0, &got, endoff);
if (ret < 0)
- goto out_put;
+ goto out;
dout("aio_write %p %llx.%llx %llu~%u got cap refs on %s\n",
inode, ceph_vinop(inode), pos + written,
@@ -763,8 +769,6 @@ retry_snap:
if (dirty)
__mark_inode_dirty(inode, dirty);
}
-
-out_put:
dout("aio_write %p %llx.%llx %llu~%u dropping cap refs on %s\n",
inode, ceph_vinop(inode), pos + written,
(unsigned)iov->iov_len - written, ceph_cap_string(got));
--
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