Xiubo Li <xiubli@xxxxxxxxxx> writes: > On 6/2/22 12:29 AM, 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 decoding the xattrs maximum size setting that is >> distributed in the mdsmap. Then, when setting an xattr, the kernel client >> 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@xxxxxxx> >> --- >> fs/ceph/mdsmap.c | 27 +++++++++++++++++++++++---- >> fs/ceph/xattr.c | 12 ++++++++---- >> include/linux/ceph/mdsmap.h | 1 + >> 3 files changed, 32 insertions(+), 8 deletions(-) >> >> * Changes since v2 >> >> Well, a lot has changed since v2! Now the xattr max value setting is >> obtained through the mdsmap, which needs to be decoded, and the feature >> that was used in the previous revision was dropped. The drawback is that >> the MDS isn't unable to know in advance if a client is aware of this xattr >> max value. >> >> * 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/mdsmap.c b/fs/ceph/mdsmap.c >> index 30387733765d..36b2bc18ca2a 100644 >> --- a/fs/ceph/mdsmap.c >> +++ b/fs/ceph/mdsmap.c >> @@ -13,6 +13,12 @@ >> #include "super.h" >> +/* >> + * 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_SIZE (1<<16) /* 64K */ >> + >> #define CEPH_MDS_IS_READY(i, ignore_laggy) \ >> (m->m_info[i].state > 0 && ignore_laggy ? true : !m->m_info[i].laggy) >> @@ -352,12 +358,10 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void >> *end, bool msgr2) >> __decode_and_drop_type(p, end, u8, bad_ext); >> } >> if (mdsmap_ev >= 8) { >> - u32 name_len; >> /* enabled */ >> ceph_decode_8_safe(p, end, m->m_enabled, bad_ext); >> - ceph_decode_32_safe(p, end, name_len, bad_ext); >> - ceph_decode_need(p, end, name_len, bad_ext); >> - *p += name_len; >> + /* fs_name */ >> + ceph_decode_skip_string(p, end, bad_ext); >> } >> /* damaged */ >> if (mdsmap_ev >= 9) { >> @@ -370,6 +374,21 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2) >> } else { >> m->m_damaged = false; >> } >> + if (mdsmap_ev >= 17) { >> + /* balancer */ >> + ceph_decode_skip_string(p, end, bad_ext); >> + /* standby_count_wanted */ >> + ceph_decode_skip_32(p, end, bad_ext); >> + /* old_max_mds */ >> + ceph_decode_skip_32(p, end, bad_ext); >> + /* min_compat_client */ >> + ceph_decode_skip_8(p, end, bad_ext); > > This is incorrect. > > If mdsmap_ev == 15 the min_compat_client will be a feature_bitset_t instead of > int8_t. Hmm... can you point me at where that's done in the code? As usual, I'm confused with that code and simply can't see that. Also, if that happens only when mdsmap_ev == 15, then there's no problem because that branch is only taken if it's >= 17. > > >> + /* required_client_features */ >> + ceph_decode_skip_set(p, end, 64, bad_ext); >> + ceph_decode_64_safe(p, end, m->m_max_xattr_size, bad_ext); >> + } else { >> + m->m_max_xattr_size = MDS_MAX_XATTR_SIZE; >> + } >> bad_ext: >> dout("mdsmap_decode m_enabled: %d, m_damaged: %d, m_num_laggy: %d\n", >> !!m->m_enabled, !!m->m_damaged, m->m_num_laggy); >> diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c >> index 8c2dc2c762a4..67f046dac35c 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->mdsmap->m_max_xattr_size)) { > > Shouldn't it be '>' instead ? Ok, I'll fix that. > We'd better always force to do a sync request with old ceph. Just check if the > mdsmap_ev < 17. It's not safe to buffer it because it maybe discarded as your > ceph PR does. Right, that can be done. So, I can simply set the m_max_xattr_size to '0' if mdsmap_ev < 17. Then, this 'if' condition will always be evaluated to true because required_blob_size will be > 0. Does that sound OK? Cheers, -- Luís > -- Xiubo > >> + dout("%s do sync setxattr: version: %llu size: %d max: %llu\n", >> + __func__, ci->i_xattrs.version, required_blob_size, >> + mdsc->mdsmap->m_max_xattr_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; >> diff --git a/include/linux/ceph/mdsmap.h b/include/linux/ceph/mdsmap.h >> index 523fd0452856..4c3e0648dc27 100644 >> --- a/include/linux/ceph/mdsmap.h >> +++ b/include/linux/ceph/mdsmap.h >> @@ -25,6 +25,7 @@ struct ceph_mdsmap { >> u32 m_session_timeout; /* seconds */ >> u32 m_session_autoclose; /* seconds */ >> u64 m_max_file_size; >> + u64 m_max_xattr_size; /* maximum size for xattrs blob */ >> u32 m_max_mds; /* expected up:active mds number */ >> u32 m_num_active_mds; /* actual up:active mds number */ >> u32 possible_max_rank; /* possible max rank index */ >>
