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Date: Fri, 27 May 2022 08:36:14 +0800 From: Xiubo Li <xiubli@...hat.com> To: Jeff Layton <jlayton@...nel.org>, Luís Henriques <lhenriques@...e.de>, Ilya Dryomov <idryomov@...il.com> Cc: ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [RFC PATCH v2] ceph: prevent a client from exceeding the MDS maximum xattr size On 5/27/22 2:39 AM, Jeff Layton wrote: > On Wed, 2022-05-25 at 18:24 +0100, Luís Henriques wrote: >> The MDS tries to enforce a limit on the total key/values in extended >> attributes. However, this limit is enforced only if doing a synchronous >> operation (MDS_OP_SETXATTR) -- if we're buffering the xattrs, the MDS >> doesn't have a chance to enforce these limits. >> >> This patch adds support for an extra feature bit that will allow the >> client to get the MDS max_xattr_pairs_size setting in the session message. >> Then, when setting an xattr, the kernel will revert to do a synchronous >> operation if that maximum size is exceeded. >> >> While there, fix a dout() that would trigger a printk warning: >> >> [ 98.718078] ------------[ cut here ]------------ >> [ 98.719012] precision 65536 too large >> [ 98.719039] WARNING: CPU: 1 PID: 3755 at lib/vsprintf.c:2703 vsnprintf+0x5e3/0x600 >> ... >> >> URL: https://tracker.ceph.com/issues/55725 >> Signed-off-by: Luís Henriques <lhenriques@...e.de> >> --- >> fs/ceph/mds_client.c | 12 ++++++++++++ >> fs/ceph/mds_client.h | 15 ++++++++++++++- >> fs/ceph/xattr.c | 12 ++++++++---- >> 3 files changed, 34 insertions(+), 5 deletions(-) >> >> * Changes since v1 >> >> Added support for new feature bit to get the MDS max_xattr_pairs_size >> setting. >> >> Also note that this patch relies on a patch that hasn't been merged yet >> ("ceph: use correct index when encoding client supported features"), >> otherwise the new feature bit won't be correctly encoded. >> >> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c >> index 35597fafb48c..87a25b7cf496 100644 >> --- a/fs/ceph/mds_client.c >> +++ b/fs/ceph/mds_client.c >> @@ -3500,6 +3500,7 @@ static void handle_session(struct ceph_mds_session *session, >> struct ceph_mds_session_head *h; >> u32 op; >> u64 seq, features = 0; >> + u64 max_xattr_pairs_size = 0; >> int wake = 0; >> bool blocklisted = false; >> >> @@ -3545,6 +3546,9 @@ static void handle_session(struct ceph_mds_session *session, >> } >> } >> >> + if (msg_version >= 6) >> + ceph_decode_64_safe(&p, end, max_xattr_pairs_size, bad); >> + >> mutex_lock(&mdsc->mutex); >> if (op == CEPH_SESSION_CLOSE) { >> ceph_get_mds_session(session); >> @@ -3552,6 +3556,12 @@ static void handle_session(struct ceph_mds_session *session, >> } >> /* FIXME: this ttl calculation is generous */ >> session->s_ttl = jiffies + HZ*mdsc->mdsmap->m_session_autoclose; >> + >> + if (max_xattr_pairs_size && (op == CEPH_SESSION_OPEN)) { >> + dout("Changing MDS max xattrs pairs size: %llu => %llu\n", >> + mdsc->max_xattr_pairs_size, max_xattr_pairs_size); >> + mdsc->max_xattr_pairs_size = max_xattr_pairs_size; >> + } >> mutex_unlock(&mdsc->mutex); >> >> mutex_lock(&session->s_mutex); >> @@ -4761,6 +4771,8 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc) >> strscpy(mdsc->nodename, utsname()->nodename, >> sizeof(mdsc->nodename)); >> >> + mdsc->max_xattr_pairs_size = MDS_MAX_XATTR_PAIRS_SIZE; >> + >> fsc->mdsc = mdsc; >> return 0; >> >> diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h >> index ca32f26f5eed..3db777df6d88 100644 >> --- a/fs/ceph/mds_client.h >> +++ b/fs/ceph/mds_client.h >> @@ -29,8 +29,11 @@ enum ceph_feature_type { >> CEPHFS_FEATURE_MULTI_RECONNECT, >> CEPHFS_FEATURE_DELEG_INO, >> CEPHFS_FEATURE_METRIC_COLLECT, >> + CEPHFS_FEATURE_ALTERNATE_NAME, >> + CEPHFS_FEATURE_NOTIFY_SESSION_STATE, >> + CEPHFS_FEATURE_MAX_XATTR_PAIRS_SIZE, > Having to make this feature-bit-dependent kind of sucks. I wonder if it > could be avoided... > > A question: > > How do the MDS's discover this setting? Do they get it from the mons? If > so, I wonder if there is a way for the clients to query the mon for this > instead of having to extend the MDS protocol? It sounds like what the "max_file_size" does, which will be recorded in the 'mdsmap'. While currently the "max_xattr_pairs_size" is one MDS's option for each daemon and could set different values for each MDS. -- Xiubo >> >> - CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_METRIC_COLLECT, >> + CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_MAX_XATTR_PAIRS_SIZE, >> }; >> >> /* >> @@ -45,9 +48,16 @@ enum ceph_feature_type { >> CEPHFS_FEATURE_MULTI_RECONNECT, \ >> CEPHFS_FEATURE_DELEG_INO, \ >> CEPHFS_FEATURE_METRIC_COLLECT, \ >> + CEPHFS_FEATURE_MAX_XATTR_PAIRS_SIZE, \ >> } >> #define CEPHFS_FEATURES_CLIENT_REQUIRED {} >> >> +/* >> + * Maximum size of xattrs the MDS can handle per inode by default. This >> + * includes the attribute name and 4+4 bytes for the key/value sizes. >> + */ >> +#define MDS_MAX_XATTR_PAIRS_SIZE (1<<16) /* 64K */ >> + >> /* >> * Some lock dependencies: >> * >> @@ -404,6 +414,9 @@ struct ceph_mds_client { >> struct rb_root quotarealms_inodes; >> struct mutex quotarealms_inodes_mutex; >> >> + /* maximum aggregate size of extended attributes on a file */ >> + u64 max_xattr_pairs_size; >> + >> /* >> * snap_rwsem will cover cap linkage into snaprealms, and >> * realm snap contexts. (later, we can do per-realm snap >> diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c >> index 8c2dc2c762a4..175a8c1449aa 100644 >> --- a/fs/ceph/xattr.c >> +++ b/fs/ceph/xattr.c >> @@ -1086,7 +1086,7 @@ static int ceph_sync_setxattr(struct inode *inode, const char *name, >> flags |= CEPH_XATTR_REMOVE; >> } >> >> - dout("setxattr value=%.*s\n", (int)size, value); >> + dout("setxattr value size: %ld\n", size); >> >> /* do request */ >> req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS); >> @@ -1184,8 +1184,14 @@ int __ceph_setxattr(struct inode *inode, const char *name, >> spin_lock(&ci->i_ceph_lock); >> retry: >> issued = __ceph_caps_issued(ci, NULL); >> - if (ci->i_xattrs.version == 0 || !(issued & CEPH_CAP_XATTR_EXCL)) >> + required_blob_size = __get_required_blob_size(ci, name_len, val_len); >> + if ((ci->i_xattrs.version == 0) || !(issued & CEPH_CAP_XATTR_EXCL) || >> + (required_blob_size >= mdsc->max_xattr_pairs_size)) { >> + dout("%s do sync setxattr: version: %llu size: %d max: %llu\n", >> + __func__, ci->i_xattrs.version, required_blob_size, >> + mdsc->max_xattr_pairs_size); >> goto do_sync; >> + } >> >> if (!lock_snap_rwsem && !ci->i_head_snapc) { >> lock_snap_rwsem = true; >> @@ -1201,8 +1207,6 @@ int __ceph_setxattr(struct inode *inode, const char *name, >> ceph_cap_string(issued)); >> __build_xattrs(inode); >> >> - required_blob_size = __get_required_blob_size(ci, name_len, val_len); >> - >> if (!ci->i_xattrs.prealloc_blob || >> required_blob_size > ci->i_xattrs.prealloc_blob->alloc_len) { >> struct ceph_buffer *blob;
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