From c0c4866f8a29a38b2bb683c267d7278e0020d90c Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Fri, 15 Dec 2023 12:51:41 -0500 Subject: [PATCH] dmu: Allow buffer fills to fail When ZFS overwrites a whole block, it does not bother to read the old content from disk. It is a good optimization, but if the buffer fill fails due to page fault or something else, the buffer ends up corrupted, neither keeping old content, nor getting the new one. On FreeBSD this is additionally complicated by page faults being blocked by VFS layer, always returning EFAULT on attempt to write from mmap()'ed but not yet cached address range. Normally it is not a big problem, since after original failure VFS will retry the write after reading the required data. The problem becomes worse in specific case when somebody tries to write into a file its own mmap()'ed content from the same location. In that situation the only copy of the data is getting corrupted on the page fault and the following retries only fixate the status quo. Block cloning makes this issue easier to reproduce, since it does not read the old data, unlike traditional file copy, that may work by chance. This patch provides the fill status to dmu_buf_fill_done(), that in case of error can destroy the corrupted buffer as if no write happened. One more complication in case of block cloning is that if error is possible during fill, dmu_buf_will_fill() must read the data via fall-back to dmu_buf_will_dirty(). It is required to allow in case of error restoring the buffer to a state after the cloning, not not before it, that would happen if we just call dbuf_undirty(). Reviewed-by: Brian Behlendorf Reviewed-by: Rob Norris Signed-off-by: Alexander Motin Sponsored by: iXsystems, Inc. Closes #15665 --- include/os/freebsd/spl/sys/uio.h | 2 +- include/os/linux/spl/sys/uio.h | 2 +- include/sys/dbuf.h | 4 ++-- lib/libspl/include/sys/uio.h | 2 +- module/os/freebsd/zfs/dmu_os.c | 4 ++-- module/zfs/dbuf.c | 33 +++++++++++++++++++++++--------- module/zfs/dmu.c | 21 +++++++++----------- module/zfs/dmu_recv.c | 2 +- 8 files changed, 41 insertions(+), 29 deletions(-) diff --git a/include/os/freebsd/spl/sys/uio.h b/include/os/freebsd/spl/sys/uio.h index b71f2f2e5..b9d41903e 100644 --- a/include/os/freebsd/spl/sys/uio.h +++ b/include/os/freebsd/spl/sys/uio.h @@ -62,7 +62,7 @@ zfs_uio_setoffset(zfs_uio_t *uio, offset_t off) } static inline void -zfs_uio_advance(zfs_uio_t *uio, size_t size) +zfs_uio_advance(zfs_uio_t *uio, ssize_t size) { zfs_uio_resid(uio) -= size; zfs_uio_offset(uio) += size; diff --git a/include/os/linux/spl/sys/uio.h b/include/os/linux/spl/sys/uio.h index a4b600004..5e6ea8d3c 100644 --- a/include/os/linux/spl/sys/uio.h +++ b/include/os/linux/spl/sys/uio.h @@ -95,7 +95,7 @@ zfs_uio_setoffset(zfs_uio_t *uio, offset_t off) } static inline void -zfs_uio_advance(zfs_uio_t *uio, size_t size) +zfs_uio_advance(zfs_uio_t *uio, ssize_t size) { uio->uio_resid -= size; uio->uio_loffset += size; diff --git a/include/sys/dbuf.h b/include/sys/dbuf.h index 1800a7e31..f2a1535c9 100644 --- a/include/sys/dbuf.h +++ b/include/sys/dbuf.h @@ -379,8 +379,8 @@ dmu_buf_impl_t *dbuf_find(struct objset *os, uint64_t object, uint8_t level, int dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags); void dmu_buf_will_clone(dmu_buf_t *db, dmu_tx_t *tx); void dmu_buf_will_not_fill(dmu_buf_t *db, dmu_tx_t *tx); -void dmu_buf_will_fill(dmu_buf_t *db, dmu_tx_t *tx); -void dmu_buf_fill_done(dmu_buf_t *db, dmu_tx_t *tx); +void dmu_buf_will_fill(dmu_buf_t *db, dmu_tx_t *tx, boolean_t canfail); +boolean_t dmu_buf_fill_done(dmu_buf_t *db, dmu_tx_t *tx, boolean_t failed); void dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx); dbuf_dirty_record_t *dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx); dbuf_dirty_record_t *dbuf_dirty_lightweight(dnode_t *dn, uint64_t blkid, diff --git a/lib/libspl/include/sys/uio.h b/lib/libspl/include/sys/uio.h index e9e21819d..665bfc423 100644 --- a/lib/libspl/include/sys/uio.h +++ b/lib/libspl/include/sys/uio.h @@ -90,7 +90,7 @@ zfs_uio_iov_at_index(zfs_uio_t *uio, uint_t idx, void **base, uint64_t *len) } static inline void -zfs_uio_advance(zfs_uio_t *uio, size_t size) +zfs_uio_advance(zfs_uio_t *uio, ssize_t size) { uio->uio_resid -= size; uio->uio_loffset += size; diff --git a/module/os/freebsd/zfs/dmu_os.c b/module/os/freebsd/zfs/dmu_os.c index a5f486b95..c33ce01ab 100644 --- a/module/os/freebsd/zfs/dmu_os.c +++ b/module/os/freebsd/zfs/dmu_os.c @@ -110,7 +110,7 @@ dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset, uint64_t size, ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size); if (tocpy == db->db_size) - dmu_buf_will_fill(db, tx); + dmu_buf_will_fill(db, tx, B_FALSE); else dmu_buf_will_dirty(db, tx); @@ -126,7 +126,7 @@ dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset, uint64_t size, } if (tocpy == db->db_size) - dmu_buf_fill_done(db, tx); + dmu_buf_fill_done(db, tx, B_FALSE); offset += tocpy; size -= tocpy; diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c index 255add6cd..280001bc3 100644 --- a/module/zfs/dbuf.c +++ b/module/zfs/dbuf.c @@ -2734,7 +2734,7 @@ dmu_buf_will_not_fill(dmu_buf_t *db_fake, dmu_tx_t *tx) } void -dmu_buf_will_fill(dmu_buf_t *db_fake, dmu_tx_t *tx) +dmu_buf_will_fill(dmu_buf_t *db_fake, dmu_tx_t *tx, boolean_t canfail) { dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake; @@ -2752,8 +2752,14 @@ dmu_buf_will_fill(dmu_buf_t *db_fake, dmu_tx_t *tx) * Block cloning: We will be completely overwriting a block * cloned in this transaction group, so let's undirty the * pending clone and mark the block as uncached. This will be - * as if the clone was never done. + * as if the clone was never done. But if the fill can fail + * we should have a way to return back to the cloned data. */ + if (canfail && dbuf_find_dirty_eq(db, tx->tx_txg) != NULL) { + mutex_exit(&db->db_mtx); + dmu_buf_will_dirty(db_fake, tx); + return; + } VERIFY(!dbuf_undirty(db, tx)); db->db_state = DB_UNCACHED; } @@ -2814,32 +2820,41 @@ dbuf_override_impl(dmu_buf_impl_t *db, const blkptr_t *bp, dmu_tx_t *tx) dl->dr_overridden_by.blk_birth = dr->dr_txg; } -void -dmu_buf_fill_done(dmu_buf_t *dbuf, dmu_tx_t *tx) +boolean_t +dmu_buf_fill_done(dmu_buf_t *dbuf, dmu_tx_t *tx, boolean_t failed) { (void) tx; dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbuf; - dbuf_states_t old_state; mutex_enter(&db->db_mtx); DBUF_VERIFY(db); - old_state = db->db_state; - db->db_state = DB_CACHED; - if (old_state == DB_FILL) { + if (db->db_state == DB_FILL) { if (db->db_level == 0 && db->db_freed_in_flight) { ASSERT(db->db_blkid != DMU_BONUS_BLKID); /* we were freed while filling */ /* XXX dbuf_undirty? */ memset(db->db.db_data, 0, db->db.db_size); db->db_freed_in_flight = FALSE; + db->db_state = DB_CACHED; DTRACE_SET_STATE(db, "fill done handling freed in flight"); + failed = B_FALSE; + } else if (failed) { + VERIFY(!dbuf_undirty(db, tx)); + db->db_buf = NULL; + dbuf_clear_data(db); + DTRACE_SET_STATE(db, "fill failed"); } else { + db->db_state = DB_CACHED; DTRACE_SET_STATE(db, "fill done"); } cv_broadcast(&db->db_changed); + } else { + db->db_state = DB_CACHED; + failed = B_FALSE; } mutex_exit(&db->db_mtx); + return (failed); } void @@ -2984,7 +2999,7 @@ dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx) DTRACE_SET_STATE(db, "filling assigned arcbuf"); mutex_exit(&db->db_mtx); (void) dbuf_dirty(db, tx); - dmu_buf_fill_done(&db->db, tx); + dmu_buf_fill_done(&db->db, tx, B_FALSE); } void diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c index 909605aa2..3215ab1c2 100644 --- a/module/zfs/dmu.c +++ b/module/zfs/dmu.c @@ -1115,14 +1115,14 @@ dmu_write_impl(dmu_buf_t **dbp, int numbufs, uint64_t offset, uint64_t size, ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size); if (tocpy == db->db_size) - dmu_buf_will_fill(db, tx); + dmu_buf_will_fill(db, tx, B_FALSE); else dmu_buf_will_dirty(db, tx); (void) memcpy((char *)db->db_data + bufoff, buf, tocpy); if (tocpy == db->db_size) - dmu_buf_fill_done(db, tx); + dmu_buf_fill_done(db, tx, B_FALSE); offset += tocpy; size -= tocpy; @@ -1330,27 +1330,24 @@ dmu_write_uio_dnode(dnode_t *dn, zfs_uio_t *uio, uint64_t size, dmu_tx_t *tx) ASSERT(size > 0); - bufoff = zfs_uio_offset(uio) - db->db_offset; + offset_t off = zfs_uio_offset(uio); + bufoff = off - db->db_offset; tocpy = MIN(db->db_size - bufoff, size); ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size); if (tocpy == db->db_size) - dmu_buf_will_fill(db, tx); + dmu_buf_will_fill(db, tx, B_TRUE); else dmu_buf_will_dirty(db, tx); - /* - * XXX zfs_uiomove could block forever (eg.nfs-backed - * pages). There needs to be a uiolockdown() function - * to lock the pages in memory, so that zfs_uiomove won't - * block. - */ err = zfs_uio_fault_move((char *)db->db_data + bufoff, tocpy, UIO_WRITE, uio); - if (tocpy == db->db_size) - dmu_buf_fill_done(db, tx); + if (tocpy == db->db_size && dmu_buf_fill_done(db, tx, err)) { + /* The fill was reverted. Undo any uio progress. */ + zfs_uio_advance(uio, off - zfs_uio_offset(uio)); + } if (err) break; diff --git a/module/zfs/dmu_recv.c b/module/zfs/dmu_recv.c index 05ca91717..54aa60259 100644 --- a/module/zfs/dmu_recv.c +++ b/module/zfs/dmu_recv.c @@ -2532,7 +2532,7 @@ receive_spill(struct receive_writer_arg *rwa, struct drr_spill *drrs, * size of the provided arc_buf_t. */ if (db_spill->db_size != drrs->drr_length) { - dmu_buf_will_fill(db_spill, tx); + dmu_buf_will_fill(db_spill, tx, B_FALSE); VERIFY0(dbuf_spill_set_blksz(db_spill, drrs->drr_length, tx)); }