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authorJan Kara <jack@suse.cz>2021-01-28 19:19:45 +0100
committerJan Kara <jack@suse.cz>2021-07-13 13:14:27 +0200
commit730633f0b7f951726e87f912a6323641f674ae34 (patch)
tree1c4a6eb5ddbc0c28e6d37a1418ec259cb6daef27 /fs/inode.c
parentc625b4cc57d078b03fd8aa4d86c99d584a1782be (diff)
mm: Protect operations adding pages to page cache with invalidate_lock
Currently, serializing operations such as page fault, read, or readahead against hole punching is rather difficult. The basic race scheme is like: fallocate(FALLOC_FL_PUNCH_HOLE) read / fault / .. truncate_inode_pages_range() <create pages in page cache here> <update fs block mapping and free blocks> Now the problem is in this way read / page fault / readahead can instantiate pages in page cache with potentially stale data (if blocks get quickly reused). Avoiding this race is not simple - page locks do not work because we want to make sure there are *no* pages in given range. inode->i_rwsem does not work because page fault happens under mmap_sem which ranks below inode->i_rwsem. Also using it for reads makes the performance for mixed read-write workloads suffer. So create a new rw_semaphore in the address_space - invalidate_lock - that protects adding of pages to page cache for page faults / reads / readahead. Reviewed-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/inode.c')
-rw-r--r--fs/inode.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/inode.c b/fs/inode.c
index c93500d84264..84c528cd1955 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -190,6 +190,8 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
mapping->private_data = NULL;
mapping->writeback_index = 0;
+ __init_rwsem(&mapping->invalidate_lock, "mapping.invalidate_lock",
+ &sb->s_type->invalidate_lock_key);
inode->i_private = NULL;
inode->i_mapping = mapping;
INIT_HLIST_HEAD(&inode->i_dentry); /* buggered by rcu freeing */