From 09bf4f5b6e6013f0ad6b090d4a8deebd4e56d878 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 15 Jun 2017 00:17:30 -0400 Subject: ufs: avoid grabbing ->truncate_mutex if possible tail unpacking is done in a wrong place; the deadlocks galore is best dealt with by doing that in ->write_iter() (and switching to iomap, while we are at it), but that's rather painful to backport. The trouble comes from grabbing pages that cover the beginning of tail from inside of ufs_new_fragments(); ongoing pageout of any of those is going to deadlock on ->truncate_mutex with process that got around to extending the tail holding that and waiting for page to get unlocked, while ->writepage() on that page is waiting on ->truncate_mutex. The thing is, we don't need ->truncate_mutex when the fragment we are trying to map is within the tail - the damn thing is allocated (tail can't contain holes). Let's do a plain lookup and if the fragment is present, we can just pretend that we'd won the race in almost all cases. The only exception is a fragment between the end of tail and the end of block containing tail. Protect ->i_lastfrag with ->meta_lock - read_seqlock_excl() is sufficient. Signed-off-by: Al Viro --- fs/ufs/inode.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) (limited to 'fs/ufs/inode.c') diff --git a/fs/ufs/inode.c b/fs/ufs/inode.c index da553ffec85b..1dda6c4875f9 100644 --- a/fs/ufs/inode.c +++ b/fs/ufs/inode.c @@ -401,13 +401,20 @@ static int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buff u64 phys64 = 0; unsigned frag = fragment & uspi->s_fpbmask; - if (!create) { - phys64 = ufs_frag_map(inode, offsets, depth); - if (phys64) - map_bh(bh_result, sb, phys64 + frag); - return 0; - } + phys64 = ufs_frag_map(inode, offsets, depth); + if (!create) + goto done; + if (phys64) { + if (fragment >= UFS_NDIR_FRAGMENT) + goto done; + read_seqlock_excl(&UFS_I(inode)->meta_lock); + if (fragment < UFS_I(inode)->i_lastfrag) { + read_sequnlock_excl(&UFS_I(inode)->meta_lock); + goto done; + } + read_sequnlock_excl(&UFS_I(inode)->meta_lock); + } /* This code entered only while writing ....? */ mutex_lock(&UFS_I(inode)->truncate_mutex); @@ -451,6 +458,11 @@ out: } mutex_unlock(&UFS_I(inode)->truncate_mutex); return err; + +done: + if (phys64) + map_bh(bh_result, sb, phys64 + frag); + return 0; } static int ufs_writepage(struct page *page, struct writeback_control *wbc) @@ -1161,7 +1173,9 @@ static void ufs_truncate_blocks(struct inode *inode) free_full_branch(inode, block, i - UFS_IND_BLOCK + 1); } } + read_seqlock_excl(&ufsi->meta_lock); ufsi->i_lastfrag = DIRECT_FRAGMENT; + read_sequnlock_excl(&ufsi->meta_lock); mark_inode_dirty(inode); mutex_unlock(&ufsi->truncate_mutex); } -- cgit v1.2.3 From a8fad984833832d5ca11a9ed64ddc55646da30e3 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 15 Jun 2017 03:57:46 -0400 Subject: ufs_truncate_blocks(): fix the case when size is in the last direct block The logics when deciding whether we need to do anything with direct blocks is broken when new size is within the last direct block. It's better to find the path to the last byte _not_ to be removed and use that instead of the path to the beginning of the first block to be freed... Signed-off-by: Al Viro --- fs/ufs/inode.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) (limited to 'fs/ufs/inode.c') diff --git a/fs/ufs/inode.c b/fs/ufs/inode.c index 1dda6c4875f9..9f4590261134 100644 --- a/fs/ufs/inode.c +++ b/fs/ufs/inode.c @@ -886,7 +886,6 @@ static inline void free_data(struct to_free *ctx, u64 from, unsigned count) ctx->to = from + count; } -#define DIRECT_BLOCK ((inode->i_size + uspi->s_bsize - 1) >> uspi->s_bshift) #define DIRECT_FRAGMENT ((inode->i_size + uspi->s_fsize - 1) >> uspi->s_fshift) static void ufs_trunc_direct(struct inode *inode) @@ -1124,19 +1123,24 @@ static void ufs_truncate_blocks(struct inode *inode) struct super_block *sb = inode->i_sb; struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi; unsigned offsets[4]; - int depth = ufs_block_to_path(inode, DIRECT_BLOCK, offsets); + int depth; int depth2; unsigned i; struct ufs_buffer_head *ubh[3]; void *p; u64 block; - if (!depth) - return; + if (inode->i_size) { + sector_t last = (inode->i_size - 1) >> uspi->s_bshift; + depth = ufs_block_to_path(inode, last, offsets); + if (!depth) + return; + } else { + depth = 1; + } - /* find the last non-zero in offsets[] */ for (depth2 = depth - 1; depth2; depth2--) - if (offsets[depth2]) + if (offsets[depth2] != uspi->s_apb - 1) break; mutex_lock(&ufsi->truncate_mutex); @@ -1145,9 +1149,8 @@ static void ufs_truncate_blocks(struct inode *inode) offsets[0] = UFS_IND_BLOCK; } else { /* get the blocks that should be partially emptied */ - p = ufs_get_direct_data_ptr(uspi, ufsi, offsets[0]); + p = ufs_get_direct_data_ptr(uspi, ufsi, offsets[0]++); for (i = 0; i < depth2; i++) { - offsets[i]++; /* next branch is fully freed */ block = ufs_data_ptr_to_cpu(sb, p); if (!block) break; @@ -1158,7 +1161,7 @@ static void ufs_truncate_blocks(struct inode *inode) write_sequnlock(&ufsi->meta_lock); break; } - p = ubh_get_data_ptr(uspi, ubh[i], offsets[i + 1]); + p = ubh_get_data_ptr(uspi, ubh[i], offsets[i + 1]++); } while (i--) free_branch_tail(inode, offsets[i + 1], ubh[i], depth - i - 1); -- cgit v1.2.3