ext4: fix ext4_dax_read/write inode locking sequence for IOCB_NOWAIT
[ Upstream commitf629afe336
] Apparently our current rwsem code doesn't like doing the trylock, then lock for real scheme. So change our dax read/write methods to just do the trylock for the RWF_NOWAIT case. This seems to fix AIM7 regression in some scalable filesystems upto ~25% in some cases. Claimed in commit942491c9e6
("xfs: fix AIM7 regression") Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Matthew Bobrowski <mbobrowski@mbobrowski.org> Tested-by: Joseph Qi <joseph.qi@linux.alibaba.com> Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com> Link: https://lore.kernel.org/r/20191212055557.11151-2-riteshh@linux.ibm.com Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -40,9 +40,10 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
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struct inode *inode = file_inode(iocb->ki_filp);
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ssize_t ret;
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if (!inode_trylock_shared(inode)) {
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if (iocb->ki_flags & IOCB_NOWAIT)
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if (iocb->ki_flags & IOCB_NOWAIT) {
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if (!inode_trylock_shared(inode))
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return -EAGAIN;
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} else {
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inode_lock_shared(inode);
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}
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/*
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@ -190,9 +191,10 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
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struct inode *inode = file_inode(iocb->ki_filp);
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ssize_t ret;
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if (!inode_trylock(inode)) {
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if (iocb->ki_flags & IOCB_NOWAIT)
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if (iocb->ki_flags & IOCB_NOWAIT) {
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if (!inode_trylock(inode))
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return -EAGAIN;
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} else {
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inode_lock(inode);
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}
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ret = ext4_write_checks(iocb, from);
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