From: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com> mainline inclusion from mainline-v6.15-rc4 commit b86629c2b2998338b4a715058b402e47d0b36206 category: feature bugzilla: https://atomgit.com/src-openeuler/kernel/issues/8862 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- EXT4 supports bigalloc feature which allows the FS to work in size of clusters (group of blocks) rather than individual blocks. This patch adds atomic write support for bigalloc so that systems with bs = ps can also create FS using - mkfs.ext4 -F -O bigalloc -b 4096 -C 16384 <dev> With bigalloc ext4 can support multi-fsblock atomic writes. We will have to adjust ext4's atomic write unit max value to cluster size. This can then support atomic write of size anywhere between [blocksize, clustersize]. This patch adds the required changes to enable multi-fsblock atomic write support using bigalloc in the next patch. In this patch for block allocation: we first query the underlying region of the requested range by calling ext4_map_blocks() call. Here are the various cases which we then handle depending upon the underlying mapping type: 1. If the underlying region for the entire requested range is a mapped extent, then we don't call ext4_map_blocks() to allocate anything. We don't need to even start the jbd2 txn in this case. 2. For an append write case, we create a mapped extent. 3. If the underlying region is entirely a hole, then we create an unwritten extent for the requested range. 4. If the underlying region is a large unwritten extent, then we split the extent into 2 unwritten extent of required size. 5. If the underlying region has any type of mixed mapping, then we call ext4_map_blocks() in a loop to zero out the unwritten and the hole regions within the requested range. This then provide a single mapped extent type mapping for the requested range. Note: We invoke ext4_map_blocks() in a loop with the EXT4_GET_BLOCKS_ZERO flag only when the underlying extent mapping of the requested range is not entirely a hole, an unwritten extent, or a fully mapped extent. That is, if the underlying region contains a mix of hole(s), unwritten extent(s), and mapped extent(s), we use this loop to ensure that all the short mappings are zeroed out. This guarantees that the entire requested range becomes a single, uniformly mapped extent. It is ok to do so because we know this is being done on a bigalloc enabled filesystem where the block bitmap represents the entire cluster unit. Note having a single contiguous underlying region of type mapped, unwrittn or hole is not a problem. But the reason to avoid writing on top of mixed mapping region is because, atomic writes requires all or nothing should get written for the userspace pwritev2 request. So if at any point in time during the write if a crash or a sudden poweroff occurs, the region undergoing atomic write should read either complete old data or complete new data. But it should never have a mix of both old and new data. So, we first convert any mixed mapping region to a single contiguous mapped extent before any data gets written to it. This is because normally FS will only convert unwritten extents to written at the end of the write in ->end_io() call. And if we allow the writes over a mixed mapping and if a sudden power off happens in between, we will end up reading mix of new data (over mapped extents) and old data (over unwritten extents), because unwritten to written conversion never went through. So to avoid this and to avoid writes getting torned due to mixed mapping, we first allocate a single contiguous block mapping and then do the write. Acked-by: Darrick J. Wong <djwong@kernel.org> Co-developed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> Link: https://patch.msgid.link/c4965ac3407cbc773f0bc954d0966d9696f5038a.1747337952... Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/ext4/ext4.h | 2 + fs/ext4/extents.c | 87 +++++++++++++++++++ fs/ext4/file.c | 7 +- fs/ext4/inode.c | 208 +++++++++++++++++++++++++++++++++++++++++++++- 4 files changed, 299 insertions(+), 5 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 948459f512b8..d3d6c6670dc9 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -3738,6 +3738,8 @@ extern long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len); extern int ext4_convert_unwritten_extents(handle_t *handle, struct inode *inode, loff_t offset, ssize_t len); +extern int ext4_convert_unwritten_extents_atomic(handle_t *handle, + struct inode *inode, loff_t offset, ssize_t len); extern int ext4_convert_unwritten_io_end_vec(handle_t *handle, ext4_io_end_t *io_end); extern int ext4_map_blocks(handle_t *handle, struct inode *inode, diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index c603ac90977c..f0f058d6370d 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4917,6 +4917,93 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len) return ret; } +/* + * This function converts a range of blocks to written extents. The caller of + * this function will pass the start offset and the size. all unwritten extents + * within this range will be converted to written extents. + * + * This function is called from the direct IO end io call back function for + * atomic writes, to convert the unwritten extents after IO is completed. + * + * Note that the requirement for atomic writes is that all conversion should + * happen atomically in a single fs journal transaction. We mainly only allocate + * unwritten extents either on a hole on a pre-exiting unwritten extent range in + * ext4_map_blocks_atomic_write(). The only case where we can have multiple + * unwritten extents in a range [offset, offset+len) is when there is a split + * unwritten extent between two leaf nodes which was cached in extent status + * cache during ext4_iomap_alloc() time. That will allow + * ext4_map_blocks_atomic_write() to return the unwritten extent range w/o going + * into the slow path. That means we might need a loop for conversion of this + * unwritten extent split across leaf block within a single journal transaction. + * Split extents across leaf nodes is a rare case, but let's still handle that + * to meet the requirements of multi-fsblock atomic writes. + * + * Returns 0 on success. + */ +int ext4_convert_unwritten_extents_atomic(handle_t *handle, struct inode *inode, + loff_t offset, ssize_t len) +{ + unsigned int max_blocks; + int ret = 0, ret2 = 0, ret3 = 0; + struct ext4_map_blocks map; + unsigned int blkbits = inode->i_blkbits; + unsigned int credits = 0; + int flags = EXT4_GET_BLOCKS_IO_CONVERT_EXT; + + map.m_lblk = offset >> blkbits; + max_blocks = EXT4_MAX_BLOCKS(len, offset, blkbits); + + if (!handle) { + /* + * TODO: An optimization can be added later by having an extent + * status flag e.g. EXTENT_STATUS_SPLIT_LEAF. If we query that + * it can tell if the extent in the cache is a split extent. + * But for now let's assume pextents as 2 always. + */ + credits = ext4_meta_trans_blocks(inode, max_blocks, 2); + } + + if (credits) { + handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS, credits); + if (IS_ERR(handle)) { + ret = PTR_ERR(handle); + return ret; + } + } + + while (ret >= 0 && ret < max_blocks) { + map.m_lblk += ret; + map.m_len = (max_blocks -= ret); + ret = ext4_map_blocks(handle, inode, &map, flags); + if (ret != max_blocks) + ext4_msg(inode->i_sb, KERN_INFO, + "inode #%lu: block %u: len %u: " + "split block mapping found for atomic write, " + "ret = %d", + inode->i_ino, map.m_lblk, + map.m_len, ret); + if (ret <= 0) + break; + } + + ret2 = ext4_mark_inode_dirty(handle, inode); + + if (credits) { + ret3 = ext4_journal_stop(handle); + if (unlikely(ret3)) + ret2 = ret3; + } + + if (ret <= 0 || ret2) + ext4_warning(inode->i_sb, + "inode #%lu: block %u: len %u: " + "returned %d or %d", + inode->i_ino, map.m_lblk, + map.m_len, ret, ret2); + + return ret > 0 ? ret2 : ret; +} + /* * This function convert a range of blocks to written extents * The caller of this function will pass the start offset and the size. diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 128a9dfe111e..4c8ddf7adc07 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -416,7 +416,12 @@ static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size, loff_t pos = iocb->ki_pos; struct inode *inode = file_inode(iocb->ki_filp); - if (!error && size && flags & IOMAP_DIO_UNWRITTEN) + + if (!error && size && (flags & IOMAP_DIO_UNWRITTEN) && + (iocb->ki_flags & IOCB_ATOMIC)) + error = ext4_convert_unwritten_extents_atomic(NULL, inode, pos, + size); + else if (!error && size && flags & IOMAP_DIO_UNWRITTEN) error = ext4_convert_unwritten_extents(NULL, inode, pos, size); if (error) return error; diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 1a7d31095b85..8f9d0e5f38cc 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3459,12 +3459,149 @@ static void ext4_set_iomap(struct inode *inode, struct iomap *iomap, } } +static int ext4_map_blocks_atomic_write_slow(handle_t *handle, + struct inode *inode, struct ext4_map_blocks *map) +{ + ext4_lblk_t m_lblk = map->m_lblk; + unsigned int m_len = map->m_len; + unsigned int mapped_len = 0, m_flags = 0; + ext4_fsblk_t next_pblk; + bool check_next_pblk = false; + int ret = 0; + + WARN_ON_ONCE(!ext4_has_feature_bigalloc(inode->i_sb)); + + /* + * This is a slow path in case of mixed mapping. We use + * EXT4_GET_BLOCKS_CREATE_ZERO flag here to make sure we get a single + * contiguous mapped mapping. This will ensure any unwritten or hole + * regions within the requested range is zeroed out and we return + * a single contiguous mapped extent. + */ + m_flags = EXT4_GET_BLOCKS_CREATE_ZERO; + + do { + ret = ext4_map_blocks(handle, inode, map, m_flags); + if (ret < 0 && ret != -ENOSPC) + goto out_err; + /* + * This should never happen, but let's return an error code to + * avoid an infinite loop in here. + */ + if (ret == 0) { + ret = -EFSCORRUPTED; + ext4_warning_inode(inode, + "ext4_map_blocks() couldn't allocate blocks m_flags: 0x%x, ret:%d", + m_flags, ret); + goto out_err; + } + /* + * With bigalloc we should never get ENOSPC nor discontiguous + * physical extents. + */ + if ((check_next_pblk && next_pblk != map->m_pblk) || + ret == -ENOSPC) { + ext4_warning_inode(inode, + "Non-contiguous allocation detected: expected %llu, got %llu, " + "or ext4_map_blocks() returned out of space ret: %d", + next_pblk, map->m_pblk, ret); + ret = -EFSCORRUPTED; + goto out_err; + } + next_pblk = map->m_pblk + map->m_len; + check_next_pblk = true; + + mapped_len += map->m_len; + map->m_lblk += map->m_len; + map->m_len = m_len - mapped_len; + } while (mapped_len < m_len); + + /* + * We might have done some work in above loop, so we need to query the + * start of the physical extent, based on the origin m_lblk and m_len. + * Let's also ensure we were able to allocate the required range for + * mixed mapping case. + */ + map->m_lblk = m_lblk; + map->m_len = m_len; + map->m_flags = 0; + + ret = ext4_map_blocks(handle, inode, map, + EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF); + if (ret != m_len) { + ext4_warning_inode(inode, + "allocation failed for atomic write request m_lblk:%u, m_len:%u, ret:%d\n", + m_lblk, m_len, ret); + ret = -EINVAL; + } + return ret; + +out_err: + /* reset map before returning an error */ + map->m_lblk = m_lblk; + map->m_len = m_len; + map->m_flags = 0; + return ret; +} + +/* + * ext4_map_blocks_atomic: Helper routine to ensure the entire requested + * range in @map [lblk, lblk + len) is one single contiguous extent with no + * mixed mappings. + * + * We first use m_flags passed to us by our caller (ext4_iomap_alloc()). + * We only call EXT4_GET_BLOCKS_ZERO in the slow path, when the underlying + * physical extent for the requested range does not have a single contiguous + * mapping type i.e. (Hole, Mapped, or Unwritten) throughout. + * In that case we will loop over the requested range to allocate and zero out + * the unwritten / holes in between, to get a single mapped extent from + * [m_lblk, m_lblk + m_len). Note that this is only possible because we know + * this can be called only with bigalloc enabled filesystem where the underlying + * cluster is already allocated. This avoids allocating discontiguous extents + * in the slow path due to multiple calls to ext4_map_blocks(). + * The slow path is mostly non-performance critical path, so it should be ok to + * loop using ext4_map_blocks() with appropriate flags to allocate & zero the + * underlying short holes/unwritten extents within the requested range. + */ +static int ext4_map_blocks_atomic_write(handle_t *handle, struct inode *inode, + struct ext4_map_blocks *map, int m_flags, + bool *force_commit) +{ + ext4_lblk_t m_lblk = map->m_lblk; + unsigned int m_len = map->m_len; + int ret = 0; + + WARN_ON_ONCE(m_len > 1 && !ext4_has_feature_bigalloc(inode->i_sb)); + + ret = ext4_map_blocks(handle, inode, map, m_flags); + if (ret < 0 || ret == m_len) + goto out; + /* + * This is a mixed mapping case where we were not able to allocate + * a single contiguous extent. In that case let's reset requested + * mapping and call the slow path. + */ + map->m_lblk = m_lblk; + map->m_len = m_len; + map->m_flags = 0; + + /* + * slow path means we have mixed mapping, that means we will need + * to force txn commit. + */ + *force_commit = true; + return ext4_map_blocks_atomic_write_slow(handle, inode, map); +out: + return ret; +} + static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map, unsigned int flags) { handle_t *handle; u8 blkbits = inode->i_blkbits; int ret, dio_credits, m_flags = 0, retries = 0; + bool force_commit = false; /* * Trim the mapping request to the maximum value that we can map at @@ -3472,7 +3609,30 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map, */ if (map->m_len > DIO_MAX_BLOCKS) map->m_len = DIO_MAX_BLOCKS; - dio_credits = ext4_chunk_trans_blocks(inode, map->m_len); + + /* + * journal credits estimation for atomic writes. We call + * ext4_map_blocks(), to find if there could be a mixed mapping. If yes, + * then let's assume the no. of pextents required can be m_len i.e. + * every alternate block can be unwritten and hole. + */ + if (flags & IOMAP_ATOMIC) { + unsigned int orig_mlen = map->m_len; + + ret = ext4_map_blocks(NULL, inode, map, 0); + if (ret < 0) + return ret; + if (map->m_len < orig_mlen) { + map->m_len = orig_mlen; + dio_credits = ext4_meta_trans_blocks(inode, orig_mlen, + map->m_len); + } else { + dio_credits = ext4_chunk_trans_blocks(inode, + map->m_len); + } + } else { + dio_credits = ext4_chunk_trans_blocks(inode, map->m_len); + } retry: /* @@ -3503,7 +3663,11 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map, else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) m_flags = EXT4_GET_BLOCKS_IO_CREATE_EXT; - ret = ext4_map_blocks(handle, inode, map, m_flags); + if (flags & IOMAP_ATOMIC) + ret = ext4_map_blocks_atomic_write(handle, inode, map, m_flags, + &force_commit); + else + ret = ext4_map_blocks(handle, inode, map, m_flags); /* * We cannot fill holes in indirect tree based inodes as that could @@ -3517,6 +3681,22 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map, if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries)) goto retry; + /* + * Force commit the current transaction if the allocation spans a mixed + * mapping range. This ensures any pending metadata updates (like + * unwritten to written extents conversion) in this range are in + * consistent state with the file data blocks, before performing the + * actual write I/O. If the commit fails, the whole I/O must be aborted + * to prevent any possible torn writes. + */ + if (ret > 0 && force_commit) { + int ret2; + + ret2 = ext4_force_commit(inode->i_sb); + if (ret2) + return ret2; + } + return ret; } @@ -3527,6 +3707,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, int ret; struct ext4_map_blocks map; u8 blkbits = inode->i_blkbits; + unsigned int orig_mlen; if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK) return -EINVAL; @@ -3540,6 +3721,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, map.m_lblk = offset >> blkbits; map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits, EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1; + orig_mlen = map.m_len; if (flags & IOMAP_WRITE) { /* @@ -3550,8 +3732,16 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, */ if (offset + length <= i_size_read(inode)) { ret = ext4_map_blocks(NULL, inode, &map, 0); - if (ret > 0 && (map.m_flags & EXT4_MAP_MAPPED)) - goto out; + /* + * For atomic writes the entire requested length should + * be mapped. + */ + if (map.m_flags & EXT4_MAP_MAPPED) { + if ((!(flags & IOMAP_ATOMIC) && ret > 0) || + (flags & IOMAP_ATOMIC && ret >= orig_mlen)) + goto out; + } + map.m_len = orig_mlen; } ret = ext4_iomap_alloc(inode, &map, flags); } else { @@ -3572,6 +3762,16 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, */ map.m_len = fscrypt_limit_io_blocks(inode, map.m_lblk, map.m_len); + /* + * Before returning to iomap, let's ensure the allocated mapping + * covers the entire requested length for atomic writes. + */ + if (flags & IOMAP_ATOMIC) { + if (map.m_len < (length >> blkbits)) { + WARN_ON_ONCE(1); + return -EINVAL; + } + } ext4_set_iomap(inode, iomap, &map, offset, length, flags); return 0; -- 2.52.0